Articles on Andrew Odendaal

AWS Step Functions: Orchestrating Complex Workflows

Wed, 01 Apr 2026 08:00:00 +0400

I deleted roughly 2,000 lines of orchestration code from our payment processing service last year. Replaced it with about 200 lines of Amazon States Language JSON. The system got more reliable, not less. That’s the short version of why I think Step Functions is one of the most underappreciated services in AWS.

The longer version involves a 3am incident, a chain of Lambda functions calling each other through direct invocation, and a payment that got charged twice because nobody could tell where the workflow had actually failed.

Terraform Testing: Unit, Integration, and End-to-End

Sat, 28 Mar 2026 08:00:00 +0400

Most Terraform code has zero tests. That’s insane for something managing production infrastructure. We wouldn’t ship application code without tests — why do we treat the thing that creates our VPCs, databases, and IAM roles like it’s somehow less important?

I learned this lesson the painful way. Last year I pushed a Terraform change that modified a security group rule on a shared networking stack. The plan looked clean. Added an ingress rule, removed an old one. Terraform showed exactly two changes. I approved it, applied it, and went to lunch. By the time I got back, three services were down. The “old” rule I removed was the one allowing traffic between our application tier and the database subnet. The plan was technically correct — it did exactly what I told it to. But I’d told it the wrong thing, and nothing in our pipeline caught it.

Distributed Tracing with OpenTelemetry: A Complete Guide

Wed, 25 Mar 2026 08:00:00 +0400

I spent four hours on a Tuesday night debugging a 30-second API call. Four hours. The call touched 12 services — auth, inventory, pricing, three different caching layers, a recommendation engine, two legacy adapters, and a handful of internal APIs that nobody remembered writing. Logs told me nothing useful. Metrics showed elevated latency somewhere in the pricing path, but “somewhere” isn’t actionable at 11pm when your on-call phone won’t stop buzzing.

Container Security Scanning in CI/CD Pipelines

Sat, 21 Mar 2026 08:00:00 +0400

If you’re not scanning container images before they hit production, it’s only a matter of time before something ugly shows up in your environment. I learned this the hard way, and I’m going to walk you through exactly how I set up container security scanning in CI/CD pipelines so you don’t repeat my mistakes.

The Wake-Up Call

About two years ago, I was running a handful of microservices on ECS. Everything was humming along. Deployments were smooth, monitoring looked clean, the team was shipping features weekly. Life was good.

AWS EventBridge: Building Event-Driven Architectures

Tue, 17 Mar 2026 08:00:00 +0400

EventBridge is the most underused AWS service. I’ll die on that hill. Teams will build these elaborate Rube Goldberg machines out of SNS topics, SQS queues, and Lambda functions stitched together with duct tape and prayers, when EventBridge would’ve given them a cleaner architecture in a fraction of the time.

I know this because I was one of those teams. About two years ago I inherited a system where a single order placement triggered a cascade of 14 SNS topics fanning out to 23 SQS queues. Nobody could tell me what happened when an order was placed without opening a spreadsheet. A spreadsheet. For message routing. When I asked why they hadn’t used EventBridge, the answer was “we started before it existed and never migrated.” Fair enough. But the pain was real — we’d get phantom duplicate processing, messages landing in DLQs with no context about where they came from, and debugging meant grepping through six different CloudWatch log groups hoping to find a correlation ID someone remembered to pass along.

Python Performance Optimization: Profiling and Tuning Guide

Sat, 14 Mar 2026 08:00:00 +0400

Don’t optimize until you’ve profiled. I’ve watched teams rewrite entire modules that weren’t even the bottleneck. Weeks of work, zero measurable improvement. The code was “cleaner” I guess, but the endpoint was still slow because the actual problem was three database queries hiding inside a template tag.

I learned this the hard way on a Django project a couple of years back. We had a view that took 4+ seconds to render. The team was convinced it was the serialization layer — we were building a big nested JSON response, lots of related objects. Someone had already started rewriting the serializers when I asked if anyone had actually profiled it. Blank stares.

Kubernetes Operators: Building Custom Controllers in Go

Tue, 10 Mar 2026 08:00:00 +0400

Operator SDK vs kubebuilder — I pick kubebuilder every time. Operator SDK wraps kubebuilder anyway, adds a layer of abstraction that mostly just gets in the way, and the documentation lags behind. Kubebuilder gives you the scaffolding, the code generation, and then gets out of your face. That’s what I want from a framework.

I built my first operator about two years ago. The task: automate database provisioning for development teams. Every time a team needed a new PostgreSQL instance, they’d file a Jira ticket, wait for the platform team to provision it, get credentials back in a Slack DM (yes, really), and manually configure their app. The whole cycle took three to five days. Sometimes longer if someone was on leave.

Rust Error Handling Patterns for Production Applications

Sat, 07 Mar 2026 08:00:00 +0400

I got paged at 3am on a Tuesday because a Rust service I’d deployed two weeks earlier crashed hard. No graceful degradation, no useful error message in the logs. Just a panic backtrace pointing at line 247 of our config parser: .unwrap().

The config file had a trailing comma that our test fixtures didn’t cover. One .unwrap() on a serde_json::from_str call, and the whole service went down. I sat there in the dark, laptop balanced on my knees, fixing a one-line bug that should never have made it past code review.

AWS CDK vs Terraform: A Practical Comparison in 2026

Tue, 03 Mar 2026 08:00:00 +0400

I use both. Terraform for multi-cloud, CDK when it’s pure AWS and the team knows TypeScript. That’s the short answer. But the long answer has a lot more nuance, and I’ve earned that nuance the hard way — including one migration that nearly broke a team’s shipping cadence for two months.

This isn’t a “which one is better” post. I don’t think that question makes sense without context. What I can tell you is where each tool shines, where each one will bite you, and how to pick the right one for your situation in 2026. I’ve shipped production infrastructure with both, maintained both in anger, and migrated between them. Here’s what I’ve learned.

Platform Engineering: Building an Internal Developer Platform

Sat, 28 Feb 2026 08:00:00 +0400

Platform engineering is DevOps done right. Or maybe it’s DevOps with a product mindset. Either way, it’s the recognition that telling every team to “own their own infrastructure” without giving them decent tooling is a recipe for chaos. I’ve watched organisations try the “you build it, you run it” approach and end up with fifteen different ways to deploy a container, nine half-configured Terraform repos, and developers who spend more time fighting YAML than writing features.

Kubernetes Horizontal Pod Autoscaling with Custom Metrics

Wed, 25 Feb 2026 08:00:00 +0400

CPU-based autoscaling is a lie for most web services. There, I said it.

I spent a painful week last year watching an HPA scale our API pods from 3 to 15 based on CPU utilization. The dashboards looked great — CPU was being “managed.” Meanwhile, the service was falling over because every single one of those 15 pods was fighting over a connection pool limited to 50 database connections. More pods made the problem worse. We were autoscaling ourselves into an outage.

Go Concurrency Patterns for Microservices

Sat, 21 Feb 2026 08:00:00 +0400

Goroutines are cheap. Goroutine leaks are not.

I learned this the hard way at 2am on a Tuesday, staring at Grafana dashboards showing one of our services consuming 40GB of RAM and climbing. The service normally sat around 500MB. We’d shipped a change three days earlier — a seemingly innocent fan-out pattern to parallelize calls to a downstream API. The code looked fine. Reviews passed. Tests passed. What we’d missed was that when the downstream service timed out, nothing was cancelling the spawned goroutines. They just… accumulated. Thousands per minute, each holding onto its request body and response buffer, waiting for a context that would never expire because we’d used context.Background() instead of propagating the parent context.

Implementing Zero-Trust Networking on AWS

Wed, 18 Feb 2026 08:00:00 +0400

VPNs are not zero trust. Stop calling them that.

I can’t count how many times I’ve sat in architecture reviews where someone points at a Site-to-Site VPN or a Client VPN endpoint and says “we’re zero trust.” No. You’ve built a tunnel. A tunnel that, once you’re inside, gives you access to everything on the network. That’s the opposite of zero trust. That’s a castle with a drawbridge and nothing inside but open hallways.

Python Type Hints and Static Analysis in Production Codebases

Sat, 14 Feb 2026 08:00:00 +0400

If you’re writing Python without type hints in 2026, you’re making life harder for everyone — including future you. I held out for a while. I liked Python’s flexibility, the duck typing, the “we’re all consenting adults here” philosophy. Then a production bug cost my team three days of debugging, and I changed my mind permanently.

I’m going to walk through how I’ve adopted type hints across production codebases, the tooling that makes it practical, and the patterns that actually matter versus the ones that are just academic noise.

AWS Cost Optimization: 15 Techniques That Actually Work

Tue, 10 Feb 2026 08:00:00 +0400

I got a call from a startup founder last year. “Our AWS bill just hit $47,000 and we have twelve engineers.” They’d been running for about eighteen months, never really looked at the bill, and suddenly it was eating their runway. I spent a week inside their account. We cut it to $28,000. That’s a 40% reduction, and honestly most of it was embarrassingly obvious stuff.

That experience crystallized something I’d been thinking about for a while: most AWS cost problems aren’t sophisticated. They’re neglect. People provision things, forget about them, and the meter keeps running. The fixes aren’t glamorous either — they’re methodical, sometimes tedious, and they work.

Kubernetes RBAC Deep Dive: Securing Multi-Tenant Clusters

Sat, 07 Feb 2026 08:00:00 +0400

I’m going to say something that’ll upset people: if your developers have cluster-admin access in production, you’re running on borrowed time. I don’t care how small your team is. I don’t care if “everyone’s responsible.” It’s insane, and I’ve got the scars to prove it.

This article is the RBAC deep dive I wish I’d had before a developer on my team ran kubectl delete namespace production-api on a Friday afternoon. Not maliciously. He thought he was pointed at his local minikube. He wasn’t. That namespace had 14 services, and we spent the weekend rebuilding it from manifests that were — let’s be generous — “mostly” up to date.

Terraform Modules: Design Patterns for Reusable Infrastructure

Tue, 03 Feb 2026 08:00:00 +0400

I once inherited a project with a single main.tf that was over 3,000 lines long. No modules. No abstractions. Just one enormous file that deployed an entire production environment — VPCs, ECS clusters, RDS instances, Lambda functions, IAM roles — all jammed together with hardcoded values and copy-pasted blocks. Changing a security group rule meant scrolling for five minutes and praying you edited the right resource. It was, without exaggeration, the worst Terraform I’ve ever seen.

GitOps with ArgoCD: From Zero to Production

Sat, 31 Jan 2026 08:00:00 +0400

ArgoCD won the GitOps war. I’ll say it. Flux is fine—it works, it’s CNCF graduated, it has its fans—but ArgoCD’s UI alone makes it worth choosing. When something’s out of sync at 2am, I don’t want to be parsing CLI output. I want to click on a resource tree and see exactly what drifted.

I’ve been running ArgoCD in production across multiple clusters for a couple of years now, and this is the guide I wish I’d had when I started. We’ll go from a fresh install to a production-grade setup with app-of-apps, RBAC, SSO, multi-cluster management, and sane sync policies.

Rust for Cloud Engineers: Why Systems Programming Matters

Tue, 27 Jan 2026 08:00:00 +0400

I started learning Rust as someone who’d spent years writing Python scripts and Go services for cloud infrastructure. My first reaction was honestly frustration — the borrow checker felt like a compiler that existed purely to reject my code. But something kept pulling me back. The binaries were tiny. The startup times were instant. And once my code compiled, it just… worked. No runtime panics at 3am. No mysterious memory leaks creeping up after a week in production.

AWS ECS vs EKS: Choosing the Right Container Orchestrator in 2026

Sat, 24 Jan 2026 08:00:00 +0400

ECS is underrated. Most teams picking EKS don’t need it. I’ve been saying this for years, and I’ll keep saying it until the industry stops treating Kubernetes as the default answer to every container question.

I watched a team — smart engineers, solid product — choose EKS for what was essentially a three-service CRUD application behind an ALB. They’d read the blog posts, watched the conference talks, and decided Kubernetes was the future. Three months later they were still stabilizing the cluster. Not building features. Not shipping value. Debugging Helm chart conflicts, fighting with the AWS VPC CNI plugin, and trying to understand why their pods kept getting evicted. The application itself worked fine. The orchestration layer was the problem.

Building Production-Ready Docker Images: A Multi-Stage Build Guide

Tue, 20 Jan 2026 08:00:00 +0400

I’ve shipped Docker images to production for years now, and the single biggest improvement I’ve made wasn’t some fancy orchestration tool or a new CI platform. It was learning to write proper multi-stage Dockerfiles. My CI pipeline used to spend 20 minutes rebuilding a bloated 2GB image every push. After switching to multi-stage builds, that image dropped to 45MB and builds finished in under 3 minutes. That’s not a typo.

Python Async Programming: asyncio, Tasks, and Real-World Patterns

Fri, 16 Jan 2026 08:00:00 +0400

I avoided asyncio for years. Callbacks, event loops, futures — it all felt like unnecessary complexity when threads worked fine. Then we had an API endpoint making 200 sequential HTTP calls to an upstream service. 45 seconds per request. We threw asyncio.gather at it and the whole thing dropped to 3 seconds. That was the moment it clicked.

Python’s async story has matured enormously. What used to be a mess of yield from and manual loop management is now clean, readable, and genuinely powerful. If you’ve been putting off learning asyncio properly, this is the guide I wish I’d had.

Kubernetes Network Policies: A Practical Security Guide

Mon, 12 Jan 2026 08:00:00 +0400

I’m going to be blunt here. If you’re running Kubernetes without network policies, every pod in your cluster can talk to every other pod. That’s a flat network. It’s terrifying.

I learned this the hard way. A few years back, a compromised container in our staging namespace made a direct TCP connection to the production PostgreSQL pod. No firewall, no segmentation, nothing stopping it. The attacker didn’t even need to be clever — they just scanned the internal network and found an open port. We had pod security policies in place, RBAC locked down, image scanning, the works. But zero network policies. That one gap made everything else irrelevant.

AWS Lambda Cold Starts: Causes, Measurement, and Mitigation Strategies

Thu, 08 Jan 2026 08:00:00 +0400

I’ve lost count of how many times someone’s told me “Lambda has cold start problems” like it’s some fatal flaw. It isn’t. Cold starts are a tradeoff. You get near-infinite scale and zero idle cost, and in return, the first request to a new execution environment takes a bit longer. That’s the deal.

The real problem is that most teams either panic about cold starts when they don’t matter, or ignore them completely when they absolutely do. I’ve seen both. We had a payment API on Lambda that was timing out on cold starts during Black Friday — the Java function took 6 seconds to initialize with Spring Boot, and our API Gateway timeout was set to 5 seconds. Every new concurrent request during the traffic spike just… failed. That was a bad day.

Terraform State Management Best Practices in 2026

Mon, 05 Jan 2026 08:00:00 +0400

I’ve been managing Terraform state across production environments for years now, and if there’s one thing I’m certain of, it’s this: state management is where most Terraform setups fall apart. Not modules. Not provider quirks. State.

The state file is Terraform’s memory. It’s how Terraform knows what it built, what changed, and what to tear down. Lose it, corrupt it, or let two people write to it at the same time, and you’re in for a rough day. I once lost a state file for a networking stack and spent the better part of 6 hours reimporting over 200 resources by hand. VPCs, subnets, route tables, NAT gateways — one at a time. Never again.

SRE Practices for Serverless Architectures: Ensuring Reliability Without Servers

Tue, 30 Dec 2025 09:00:00 +0400

Serverless architectures have transformed how organizations build and deploy applications, offering benefits like reduced operational overhead, automatic scaling, and consumption-based pricing. However, the ephemeral nature of serverless functions, limited execution contexts, and distributed architecture introduce unique reliability challenges. Site Reliability Engineering (SRE) practices must evolve to address these challenges while maintaining the core principles of reliability, observability, and automation.

This comprehensive guide explores how to apply SRE practices to serverless architectures, with practical examples and implementation strategies for ensuring reliability in environments where you don’t manage the underlying infrastructure.

Rust Year in Review: 2025's Major Milestones and Achievements

Thu, 25 Dec 2025 08:00:00 +0400

As 2025 draws to a close, it’s time to look back on what has been an extraordinary year for the Rust programming language. From significant language enhancements and ecosystem growth to expanding industry adoption and community achievements, Rust has continued its impressive trajectory. What began as Mozilla’s research project has evolved into a mainstream programming language that’s reshaping how we think about systems programming, web development, and beyond.

In this comprehensive year-in-review, we’ll explore the major milestones and achievements that defined Rust in 2025. We’ll examine the language improvements that landed, the ecosystem developments that expanded Rust’s capabilities, the industry adoption trends that solidified its position, and the community growth that fueled its success. Whether you’ve been following Rust closely throughout the year or are just catching up, this retrospective will provide valuable insights into Rust’s evolution over the past twelve months.

AI-Driven Cybersecurity: Advanced Threat Detection and Response

Tue, 16 Dec 2025 10:30:00 +0400

The cybersecurity landscape has reached a critical inflection point. As threat actors deploy increasingly sophisticated attacks using automation and artificial intelligence, traditional security approaches are struggling to keep pace. Security teams face overwhelming volumes of alerts, complex attack patterns, and a persistent shortage of skilled personnel. In response, organizations are turning to AI-driven cybersecurity solutions to detect, analyze, and respond to threats with greater speed and accuracy than ever before.

Rust in 2025: Future Directions and Predictions

Mon, 15 Dec 2025 08:00:00 +0400

As 2025 draws to a close, the Rust programming language continues its impressive trajectory of growth and adoption. From its humble beginnings as Mozilla’s research project to its current status as a mainstream language used by tech giants and startups alike, Rust has proven that its unique combination of safety, performance, and expressiveness fills a critical gap in the programming language landscape. But what lies ahead for Rust in 2025? What new features, ecosystem developments, and adoption trends can we expect to see?

Rust for AI and Machine Learning in 2025: Libraries, Performance, and Use Cases

Fri, 05 Dec 2025 08:00:00 +0400

Artificial Intelligence and Machine Learning continue to transform industries across the globe, driving innovations in everything from healthcare and finance to autonomous vehicles and creative tools. While Python has long dominated the AI/ML landscape due to its extensive ecosystem and ease of use, Rust has been steadily gaining ground as a compelling alternative for performance-critical components and production deployments. With its focus on safety, speed, and concurrency, Rust offers unique advantages for AI/ML workloads that require efficiency and reliability.

DevOps for Edge Computing: Extending CI/CD to the Network Edge

Tue, 02 Dec 2025 09:00:00 +0400

The rise of edge computing is transforming how organizations deploy and manage applications. By moving computation closer to data sources and end users, edge computing reduces latency, conserves bandwidth, and enables new use cases that weren’t previously possible. However, this distributed architecture introduces significant challenges for DevOps teams accustomed to centralized cloud environments.

This comprehensive guide explores how to extend DevOps principles and practices to edge computing environments, enabling reliable, secure, and scalable deployments across potentially thousands of edge locations.

FinOps Practices for Cloud Cost Optimization in Distributed Systems

Mon, 01 Dec 2025 08:00:00 +0400

As organizations increasingly adopt distributed systems in the cloud, managing and optimizing costs has become a critical challenge. The dynamic, scalable nature of cloud resources that makes distributed systems powerful can also lead to unexpected expenses and inefficiencies if not properly managed. This is where FinOps—the practice of bringing financial accountability to cloud spending—comes into play.

This article explores practical FinOps strategies and techniques for optimizing cloud costs in distributed systems without compromising performance, reliability, or security.

Hiring Cloud Engineers: What to Look For

Mon, 01 Dec 2025 08:00:00 +0400

As organizations accelerate their cloud adoption journeys, the demand for skilled cloud engineers has skyrocketed. Building a high-performing cloud team is now a critical competitive advantage, yet finding and retaining top cloud talent remains one of the most significant challenges facing technology leaders today. The rapid evolution of cloud technologies, combined with a global shortage of experienced professionals, has created a fiercely competitive hiring landscape.

This comprehensive guide explores what to look for when hiring cloud engineers, from essential technical skills and certifications to soft skills and cultural fit. Whether you’re building a cloud team from scratch or expanding an existing one, this guide provides actionable strategies for attracting, assessing, and retaining the cloud talent your organization needs to succeed.

Rust Best Practices for Maintainable Code in 2025

Tue, 25 Nov 2025 08:00:00 +0400

Writing code that works is just the first step in software development. For projects that need to evolve and be maintained over time, code quality and maintainability are just as important as functionality. Rust, with its emphasis on safety and correctness, provides many tools and patterns that can help you write code that’s not only correct but also maintainable. However, like any language, it requires discipline and adherence to best practices to ensure your codebase remains clean, understandable, and sustainable.

Service Mesh Architecture: The SRE's Guide to Network Reliability

Tue, 18 Nov 2025 10:00:00 +0400

As organizations adopt microservices architectures, the complexity of service-to-service communication grows exponentially. Managing this communication layer—including routing, security, reliability, and observability—has become one of the most challenging aspects of operating modern distributed systems. Service mesh architecture has emerged as a powerful solution to these challenges, providing a dedicated infrastructure layer that handles service-to-service communication.

This comprehensive guide explores service mesh architecture from an SRE perspective, focusing on how it enhances reliability, security, and observability in microservices environments.

Rust in Industry: Case Studies and Success Stories in 2025

Sat, 15 Nov 2025 08:00:00 +0400

Since its 1.0 release in 2015, Rust has steadily gained adoption across various industries, from tech giants to startups, and from web services to embedded systems. What began as Mozilla’s research project has evolved into a mainstream programming language that companies increasingly rely on for performance-critical, secure, and reliable systems. As we look at the landscape in 2025, Rust’s adoption has reached new heights, with more organizations than ever using it to solve real-world problems.

Rust Compared to Other Programming Languages: A Comprehensive Analysis

Wed, 05 Nov 2025 08:00:00 +0400

Choosing the right programming language for a project is a critical decision that can significantly impact development speed, code quality, performance, and maintainability. Rust, with its focus on memory safety without garbage collection, has carved out a unique position in the programming language landscape. But how does it compare to other popular languages like C/C++, Go, Java, Python, and JavaScript? Understanding these comparisons can help you make informed decisions about when and why to choose Rust for your projects.

AI-Powered Data Analytics: Transforming Enterprise Decision Making

Tue, 04 Nov 2025 10:00:00 +0400

The volume, velocity, and variety of data that organizations generate today have far outpaced traditional analytics methods. As businesses struggle to extract meaningful insights from increasingly complex datasets, artificial intelligence has emerged as a transformative force in data analytics. AI-powered analytics goes beyond conventional approaches by automating pattern detection, generating predictive insights, and even recommending actions based on data-driven findings.

This comprehensive guide explores how AI is revolutionizing data analytics, with practical implementation strategies and real-world examples to help organizations harness the full potential of their data assets.

Common Cloud Security Misconfigurations: Detection and Remediation

Sat, 01 Nov 2025 08:00:00 +0400

Cloud security misconfigurations have become one of the leading causes of data breaches and security incidents. As organizations rapidly adopt cloud services and infrastructure, the complexity of configurations increases, creating numerous opportunities for security gaps. According to recent industry reports, misconfigurations account for nearly 65-70% of cloud security incidents, making them a critical area of focus for security teams.

This comprehensive guide explores common cloud security misconfigurations across major cloud providers (AWS, Azure, and Google Cloud), providing detailed detection methods, remediation strategies, and prevention techniques. Whether you’re a cloud architect, security engineer, or DevOps professional, this guide will help you identify and address the most prevalent security risks in your cloud environments.

Rust's Design Philosophy and Principles: Understanding the Language's Core Values

Sat, 25 Oct 2025 08:00:00 +0400

Every programming language embodies a set of values and principles that guide its design decisions and evolution. Rust, with its unique combination of memory safety, performance, and expressiveness, is built on a foundation of carefully considered principles that shape everything from its syntax to its type system. Understanding these principles not only helps you write better Rust code but also provides insight into why Rust works the way it does and how to make decisions that align with the language’s philosophy.

Container Security Best Practices: Protecting Your Containerized Applications

Tue, 21 Oct 2025 09:30:00 +0400

As organizations increasingly adopt containerization for application deployment, securing these environments has become a critical concern. Containers introduce unique security challenges that differ from traditional infrastructure, requiring specialized approaches and tools. From vulnerable base images to insecure runtime configurations, the attack surface for containerized applications is substantial and often overlooked.

This comprehensive guide explores container security best practices across the entire container lifecycle, providing practical strategies and tools to help DevOps teams build and maintain secure containerized environments.

Go Distributed Consensus: Implementing Raft and Leader Election

Tue, 07 Oct 2025 11:00:00 +0400

In distributed systems, one of the most challenging problems is achieving consensus among a group of nodes that may experience failures, network partitions, and message delays. How do we ensure that a cluster of servers agrees on a shared state when any node might fail at any time? This fundamental problem underlies many distributed systems challenges, from database replication to distributed locking and coordination services.

Distributed consensus algorithms provide a solution by enabling a collection of machines to work as a coherent group that can survive the failures of some of its members. Among these algorithms, Raft has emerged as one of the most widely implemented due to its focus on understandability and practical implementation. Unlike more complex algorithms like Paxos, Raft was designed to be comprehensible and implementable, making it an excellent choice for Go developers building distributed systems.

Observability Patterns for Distributed Systems: Beyond Metrics, Logs, and Traces

Tue, 07 Oct 2025 10:00:00 +0400

In today’s world of microservices, serverless functions, and complex distributed systems, traditional monitoring approaches fall short. Modern systems generate vast amounts of telemetry data across numerous components, making it challenging to understand system behavior, identify issues, and troubleshoot problems. This is where observability comes in—providing deep insights into what’s happening inside your systems without having to deploy new code to add instrumentation.

This comprehensive guide explores advanced observability patterns for distributed systems, going beyond the basic “three pillars” of metrics, logs, and traces to help SRE teams build more observable systems and solve complex problems faster.

Data Mesh Architecture: A Paradigm Shift for Distributed Data

Wed, 01 Oct 2025 08:00:00 +0400

As organizations scale their data initiatives, traditional centralized data architectures—data warehouses, data lakes, and even lake houses—often struggle to keep pace with the growing complexity and domain diversity of modern enterprises. Data Mesh has emerged as a paradigm shift in how we think about and implement data architectures, particularly in distributed systems.

This article explores the principles, implementation patterns, and practical considerations for adopting Data Mesh architecture in distributed systems.

AI-Powered Code Generation: Transforming Enterprise Software Development

Tue, 16 Sep 2025 09:00:00 +0400

The landscape of software development is undergoing a profound transformation with the rise of AI-powered code generation tools. What began as simple code completion features has evolved into sophisticated systems capable of generating entire functions, classes, and even applications from natural language descriptions. For enterprise organizations, these tools offer unprecedented opportunities to accelerate development cycles, reduce technical debt, and allow developers to focus on higher-value creative work.

This comprehensive guide explores how enterprises can effectively implement AI code generation tools, establish appropriate governance frameworks, and maximize developer productivity while maintaining code quality and security.

Rust Package Management with Cargo: Beyond the Basics

Mon, 15 Sep 2025 08:00:00 +0400

Cargo, Rust’s package manager and build system, is one of the language’s greatest strengths. It handles dependency management, compilation, testing, documentation generation, and package publishing, providing a seamless experience for Rust developers. While most Rust programmers are familiar with basic Cargo commands like cargo build and cargo test, the tool offers a wealth of advanced features that can significantly improve your development workflow and help you manage complex projects more effectively.

Rust Documentation Practices: Creating Clear, Comprehensive, and Useful Docs

Fri, 05 Sep 2025 08:00:00 +0400

Documentation is a crucial aspect of software development, serving as a bridge between code authors and users. Well-written documentation helps users understand how to use your code, explains why certain design decisions were made, and guides contributors on how to extend or modify your project. Rust takes documentation seriously, providing first-class tools and conventions that make it easy to create clear, comprehensive, and useful documentation directly alongside your code.

In this comprehensive guide, we’ll explore Rust’s documentation ecosystem, from inline doc comments to full-fledged documentation websites. You’ll learn how to write effective documentation, leverage Rust’s documentation tools, and follow best practices that have emerged in the Rust community. By the end, you’ll have a solid understanding of how to create documentation that enhances the quality and usability of your Rust projects, whether you’re working on a small library or a large-scale application.

GitOps for Multi-Environment Deployments: Scaling Infrastructure as Code

Tue, 02 Sep 2025 10:30:00 +0400

As organizations scale their cloud-native applications, managing deployments across multiple environments—from development and staging to production and disaster recovery—becomes increasingly complex. GitOps has emerged as a powerful paradigm for managing this complexity by using Git as the single source of truth for declarative infrastructure and applications.

This comprehensive guide explores how to implement GitOps practices for multi-environment deployments, providing practical strategies and tools to ensure consistency, security, and scalability across your entire deployment pipeline.

SOC 2 and ISO 27001 for SaaS Companies: A Comprehensive Implementation Guide

Mon, 01 Sep 2025 08:00:00 +0400

For SaaS companies, security and compliance have evolved from optional differentiators to essential business requirements. As organizations increasingly rely on cloud-based solutions to handle sensitive data, customers and partners demand assurance that their information is protected according to recognized standards. SOC 2 and ISO 27001 have emerged as the two most important compliance frameworks for SaaS providers, serving as trusted indicators of security maturity and risk management capabilities.

This comprehensive guide explores the implementation of SOC 2 and ISO 27001 for SaaS companies. We’ll cover the requirements, implementation strategies, certification processes, and approaches for maintaining ongoing compliance. Whether you’re just starting your compliance journey or looking to enhance your existing security program, this guide provides actionable insights to help you achieve and maintain these critical certifications.

Testing and Debugging in Rust: Ensuring Code Quality and Reliability

Mon, 25 Aug 2025 08:00:00 +0400

Testing and debugging are essential aspects of software development, ensuring that code works as expected and helping to identify and fix issues when it doesn’t. Rust provides a rich set of tools and features for testing and debugging, from built-in unit testing frameworks to advanced property-based testing libraries and powerful debugging capabilities. These tools, combined with Rust’s strong type system and ownership model, help developers catch bugs early and build reliable, maintainable software.

Quantum Computing for Enterprise: Implementation Guide

Mon, 25 Aug 2025 00:00:00 +0000

Understand quantum computing applications in enterprise environments.

Understanding Quantum Computing

Quantum Computing Fundamentals

Key concepts that distinguish quantum from classical computing:

Quantum Bits (Qubits):

Unlike classical bits (0 or 1), qubits can exist in superposition
Can represent multiple states simultaneously
Enable quantum computers to process vast amounts of information
Current systems have dozens to hundreds of qubits
Future fault-tolerant systems will require millions

Quantum Superposition:

Qubits can exist in multiple states at once
Allows quantum computers to explore multiple solutions simultaneously
Creates exponential scaling of computational space
Enables certain algorithms to achieve dramatic speedups

Quantum Entanglement:

Rust's Security Features: Building Robust, Vulnerability-Free Software

Fri, 15 Aug 2025 08:00:00 +0400

Security vulnerabilities continue to plague software systems, with memory safety issues like buffer overflows, use-after-free, and data races accounting for a significant percentage of critical CVEs (Common Vulnerabilities and Exposures). Rust was designed from the ground up with security in mind, offering a unique approach that prevents these classes of bugs at compile time without sacrificing performance. This “security by design” philosophy has made Rust increasingly popular for security-critical applications, from operating systems and browsers to cryptographic libraries and network services.

SRE Incident Management: Response and Recovery

Mon, 11 Aug 2025 00:00:00 +0000

Implement effective incident management processes.

The Foundations of Effective Incident Management

Before diving into specific practices, let’s establish the core principles that underpin effective incident management:

Key Principles

Blameless Culture: Focus on systems and processes, not individuals
Preparedness: Plan and practice for incidents before they occur
Clear Ownership: Define roles and responsibilities clearly
Proportional Response: Match the response to the severity of the incident
Continuous Learning: Use incidents as opportunities to improve

The Incident Lifecycle

Understanding the complete incident lifecycle helps teams develop comprehensive management strategies:

Transfer Learning Techniques: Leveraging Pre-trained Models for Enterprise AI Applications

Tue, 05 Aug 2025 09:45:00 +0400

In the rapidly evolving field of artificial intelligence, transfer learning has emerged as one of the most powerful techniques for building effective models with limited data and computational resources. By leveraging knowledge gained from pre-trained models, organizations can significantly reduce the time, data, and computing power needed to develop high-performing AI applications.

This comprehensive guide explores practical transfer learning techniques that can help enterprise teams build sophisticated AI solutions even when faced with constraints on data availability and computational resources.

Serverless Architecture Patterns for Distributed Systems

Tue, 05 Aug 2025 08:00:00 +0400

Serverless computing has revolutionized how we build and deploy distributed systems, offering a model where cloud providers dynamically manage the allocation and provisioning of servers. This approach allows developers to focus on writing code without worrying about infrastructure management, scaling, or maintenance. As serverless architectures mature, distinct patterns have emerged that address common challenges in distributed systems.

This article explores key serverless architecture patterns, providing practical implementation examples and guidance on when to apply each pattern in your distributed systems.

The Future of Rust: Roadmap and Upcoming Features

Tue, 05 Aug 2025 08:00:00 +0400

Since its 1.0 release in 2015, Rust has evolved from a promising systems programming language into a mature, production-ready technology used by companies and developers worldwide. Its unique combination of performance, safety, and ergonomics has driven adoption across various domains, from operating systems and embedded devices to web services and game development. As we look to the future, Rust continues to evolve with an ambitious roadmap that aims to address current limitations, expand into new domains, and further improve developer experience.

Microservices Architecture Patterns: Design Strategies for Scalable Systems

Tue, 22 Jul 2025 10:15:00 +0400

Microservices architecture has become the dominant approach for building complex, scalable applications. By breaking down monolithic applications into smaller, independently deployable services, organizations can achieve greater agility, scalability, and resilience. However, implementing microservices effectively requires careful consideration of numerous design patterns and architectural decisions.

This comprehensive guide explores proven microservices architecture patterns that help teams navigate the complexities of distributed systems while avoiding common pitfalls. Whether you’re planning a new microservices implementation or refining an existing one, these patterns will provide valuable strategies for building robust, maintainable systems.

Service Discovery in Distributed Systems: Patterns and Implementation

Sun, 20 Jul 2025 08:00:00 +0400

In distributed systems, particularly microservices architectures, services need to find and communicate with each other efficiently. As systems scale and become more dynamic—with services being deployed, scaled, and terminated frequently—hardcoded network locations become impractical. This is where service discovery comes in, providing mechanisms for services to locate each other dynamically at runtime.

This article explores various service discovery patterns, their implementation approaches, and best practices for building robust service discovery mechanisms in distributed systems.

Rust Interoperability: Seamlessly Working with Other Languages

Tue, 15 Jul 2025 08:00:00 +0400

One of Rust’s greatest strengths is its ability to interoperate with other programming languages. This interoperability allows developers to gradually introduce Rust into existing projects, leverage specialized libraries from other ecosystems, and build components that can be used across different platforms and languages. Whether you’re looking to speed up a Python application with Rust, integrate Rust components into a C++ codebase, or expose Rust functionality to JavaScript, the language provides robust tools and patterns for seamless integration.

Edge Computing Architectures: Bringing Computation Closer to Data Sources

Thu, 10 Jul 2025 08:00:00 +0400

As data volumes grow exponentially and latency requirements become more stringent, traditional cloud computing models face increasing challenges. Edge computing has emerged as a powerful paradigm that brings computation and data storage closer to the sources of data, enabling faster processing, reduced bandwidth usage, and new capabilities for real-time applications. From IoT devices and autonomous vehicles to content delivery and industrial automation, edge computing is transforming how we architect distributed systems.

Automated Remediation: Building Self-Healing Systems for Modern SRE Teams

Tue, 08 Jul 2025 09:30:00 +0400

In the world of Site Reliability Engineering (SRE), the goal has always been to reduce toil—repetitive, manual work that adds little value and scales linearly with service growth. One of the most effective ways to achieve this is through automated remediation: the practice of automatically detecting and fixing common issues without human intervention. By building self-healing systems, SRE teams can not only improve reliability but also free up valuable time for strategic engineering work.

SRE Capacity Planning: Resource Management

Tue, 01 Jul 2025 00:00:00 +0000

Master capacity planning techniques.

Understanding Capacity Planning for SRE

Before diving into specific methodologies, let’s establish what capacity planning means in the context of Site Reliability Engineering.

What is Capacity Planning?

Capacity planning is the process of determining the resources required to meet expected workloads while maintaining service level objectives (SLOs). For SRE teams, this involves:

Forecasting demand: Predicting future workload based on historical data and business projections
Resource modeling: Understanding how workload translates to resource requirements
Capacity allocation: Provisioning appropriate resources across services and regions
Performance analysis: Ensuring systems meet performance targets under expected load
Cost optimization: Balancing reliability requirements with infrastructure costs

Why Capacity Planning Matters for SRE

Effective capacity planning directly impacts several key aspects of reliability engineering:

Rust's Ecosystem and Community: The Foundation of Success

Wed, 25 Jun 2025 08:00:00 +0400

A programming language is more than just syntax and features—it’s also the ecosystem of libraries, tools, and resources that surround it, and the community of people who use, develop, and advocate for it. Rust has distinguished itself not only through its technical merits but also through its exceptionally vibrant ecosystem and welcoming community. From the comprehensive package manager Cargo to the collaborative governance model, Rust’s ecosystem and community have been instrumental in the language’s growing adoption and success.

Data Consistency Models in Distributed Systems

Fri, 20 Jun 2025 08:00:00 +0400

In distributed systems, one of the most challenging aspects is managing data consistency across multiple nodes. The CAP theorem tells us that we can’t simultaneously achieve perfect consistency, availability, and partition tolerance—we must make trade-offs. Understanding these trade-offs and the spectrum of consistency models is crucial for designing distributed systems that meet your specific requirements.

This article explores the various consistency models available in distributed systems, from strong consistency to eventual consistency, and provides guidance on selecting the appropriate model for your application needs.

Building an AI Ethics and Governance Framework for Enterprise Applications

Tue, 17 Jun 2025 11:30:00 +0400

As artificial intelligence becomes increasingly embedded in enterprise applications and decision-making processes, organizations face growing pressure to ensure their AI systems are developed and deployed responsibly. Beyond regulatory compliance, implementing robust AI ethics and governance frameworks has become a business imperative—protecting against reputational damage, enhancing customer trust, and mitigating risks associated with AI deployment.

This comprehensive guide explores how to build and implement an effective AI ethics and governance framework for enterprise applications, providing practical strategies and tools that technical leaders can use to ensure responsible AI development and deployment.

Machine Learning with Rust: Performance and Safety for AI Applications

Sun, 15 Jun 2025 08:00:00 +0400

Machine learning has traditionally been dominated by languages like Python, which offer ease of use and a rich ecosystem of libraries. However, as models grow larger and performance requirements become more demanding, there’s increasing interest in alternatives that can provide better efficiency without sacrificing developer productivity. Rust, with its focus on performance, safety, and modern language features, is emerging as a compelling option for machine learning applications, particularly in production environments where speed and reliability are critical.

Site Reliability Engineering Fundamentals: Building and Scaling Reliable Services

Sun, 15 Jun 2025 08:00:00 +0400

Site Reliability Engineering (SRE) has emerged as a critical discipline at the intersection of software engineering and operations. Pioneered by Google and now adopted by organizations of all sizes, SRE applies software engineering principles to operations and infrastructure challenges, with a focus on creating scalable and highly reliable software systems. As distributed systems grow more complex, the principles and practices of SRE have become essential for maintaining service reliability while enabling rapid innovation.

Data Engineering Best Practices: Building Robust Pipelines

Thu, 12 Jun 2025 00:00:00 +0000

Master data engineering principles.

Data Pipeline Architecture

Architectural Patterns

Foundational approaches to data pipeline design:

Batch Processing:

Processing data in scheduled intervals
Handling large volumes efficiently
Optimizing for throughput over latency
Implementing idempotent operations
Managing dependencies between jobs

Stream Processing:

Processing data in near real-time
Handling continuous data flows
Implementing windowing strategies
Managing state and checkpointing
Ensuring exactly-once processing

Lambda Architecture:

Combining batch and streaming layers
Providing both accurate and real-time views
Managing duplicate processing logic
Reconciling batch and speed layers
Optimizing for different access patterns

Kappa Architecture:

API Design for Distributed Systems: Principles and Best Practices

Thu, 05 Jun 2025 08:00:00 +0400

In distributed systems, APIs serve as the critical interfaces between services, enabling communication, integration, and collaboration across components. Well-designed APIs can significantly enhance system flexibility, maintainability, and scalability, while poorly designed ones can lead to tight coupling, performance bottlenecks, and brittle architectures. As organizations increasingly adopt microservices and distributed architectures, mastering API design has become an essential skill for modern software engineers.

This article explores key principles, patterns, and best practices for designing effective APIs in distributed systems, with practical examples to guide your implementation.

Game Development with Rust: Building Fast, Reliable Games

Thu, 05 Jun 2025 08:00:00 +0400

Game development demands a unique combination of performance, reliability, and expressiveness from programming languages. Traditionally dominated by C++ for its speed and control, the field is now seeing growing interest in Rust as an alternative. Rust offers comparable performance to C++ while eliminating entire classes of bugs through its ownership system and providing modern language features that improve developer productivity. From indie 2D games to high-performance game engines, Rust is proving to be a compelling choice for game developers.

DevSecOps Implementation Guide: Integrating Security into the Development Lifecycle

Tue, 03 Jun 2025 08:00:00 +0400

As organizations accelerate their digital transformation and software delivery, security can no longer be an afterthought or a final checkpoint before deployment. DevSecOps—the integration of security practices within the DevOps process—has emerged as a critical approach for building secure applications from the ground up. By embedding security throughout the software development lifecycle, organizations can deliver secure, compliant applications without sacrificing speed or agility.

This comprehensive guide explores the principles, practices, tools, and cultural changes needed to successfully implement DevSecOps in your organization. Whether you’re just starting your DevSecOps journey or looking to enhance your existing practices, this guide provides actionable strategies to integrate security into every phase of your development process.

Embedded Systems Programming with Rust: Safety and Performance for Resource-Constrained Devices

Sun, 25 May 2025 08:00:00 +0400

Embedded systems programming has traditionally been dominated by C and C++, languages that offer the low-level control and performance necessary for resource-constrained environments. However, these languages also come with significant drawbacks, particularly in terms of memory safety and modern language features. Rust offers a compelling alternative, providing the same level of control and performance while eliminating entire classes of bugs through its ownership system and zero-cost abstractions.

In this comprehensive guide, we’ll explore how Rust is changing the landscape of embedded systems development. From bare-metal programming on microcontrollers to higher-level abstractions for IoT devices, you’ll learn how Rust’s unique features make it an excellent choice for embedded applications. By the end, you’ll understand how to leverage Rust’s safety and performance for your own embedded projects, whether you’re building a simple sensor node or a complex industrial control system.

Monitoring and Observability in Distributed Systems

Sun, 25 May 2025 08:00:00 +0400

In the world of distributed systems, understanding what’s happening across your services is both critical and challenging. As systems grow in complexity—spanning multiple services, data stores, and infrastructure components—traditional monitoring approaches fall short. This is where modern monitoring and observability practices come into play, providing the visibility needed to operate distributed systems with confidence.

This article explores the evolution from basic monitoring to comprehensive observability, providing practical guidance on implementing effective observability practices in distributed systems.

Real-Time Data Processing: Stream Analytics

Sun, 25 May 2025 00:00:00 +0000

Build real-time data processing systems using stream processing frameworks.

Real-Time Data Processing Fundamentals

Core Concepts and Terminology

Understanding the building blocks of real-time systems:

Real-Time Processing vs. Batch Processing:

Real-time: Continuous processing with minimal latency
Batch: Periodic processing of accumulated data
Micro-batch: Small batches with higher frequency
Near real-time: Low but not immediate latency
Stream processing: Continuous data flow processing

Key Concepts:

Events: Discrete data records representing occurrences
Streams: Unbounded sequences of events
Producers: Systems generating event data
Consumers: Systems processing event data
Topics/Channels: Named streams for event organization
Partitions: Subdivisions of streams for parallelism
Offsets: Positions within event streams

Processing Semantics:

Event-Driven Architecture Patterns: Building Responsive and Scalable Systems

Thu, 15 May 2025 08:00:00 +0400

Event-driven architecture (EDA) has emerged as a powerful architectural paradigm for building responsive, scalable, and resilient distributed systems. By decoupling components through asynchronous event-based communication, EDA enables organizations to build systems that can handle complex workflows, scale independently, and evolve more flexibly than traditional request-response architectures. However, implementing EDA effectively requires understanding various patterns, technologies, and trade-offs.

This comprehensive guide explores event-driven architecture patterns, covering event sourcing, CQRS, message brokers, stream processing, and implementation strategies. Whether you’re designing a new system or evolving an existing one, these insights will help you leverage event-driven approaches to build systems that can adapt to changing business requirements while maintaining performance, reliability, and maintainability.

Web Development with Rust: An Introduction to Building Fast, Secure Web Applications

Thu, 15 May 2025 08:00:00 +0400

Web development with Rust is gaining momentum as developers seek alternatives that offer better performance, improved security, and fewer runtime surprises than traditional web stacks. While Rust wasn’t initially designed for web development, its emphasis on safety, speed, and concurrency makes it an excellent fit for modern web applications that need to be reliable and efficient. From low-level HTTP servers to full-stack frameworks, the Rust ecosystem now offers a variety of tools for building web applications at different levels of abstraction.

Testing Distributed Systems: Strategies for Ensuring Reliability

Sat, 10 May 2025 08:00:00 +0400

Testing distributed systems presents unique challenges that go far beyond traditional application testing. With components spread across multiple machines, complex network interactions, and various failure modes, ensuring reliability requires specialized testing strategies. Traditional testing approaches often fall short when confronted with the complexities of distributed environments, where issues like network partitions, race conditions, and partial failures can lead to subtle and hard-to-reproduce bugs.

This article explores comprehensive testing strategies for distributed systems, providing practical approaches to validate functionality, performance, and resilience across distributed components.

AI Anomaly Detection Systems: Architectures and Implementation

Mon, 05 May 2025 08:00:00 +0400

Anomaly detection has become a critical capability for modern organizations, enabling them to identify unusual patterns that could indicate security breaches, system failures, performance issues, or business opportunities. With the explosion of data from infrastructure, applications, and business processes, traditional rule-based approaches to anomaly detection are no longer sufficient. This is where AI-powered anomaly detection systems come in, offering the ability to automatically learn normal patterns and identify deviations without explicit programming.

GraphQL API Design Best Practices: Building Flexible and Efficient APIs

Thu, 01 May 2025 08:00:00 +0400

GraphQL has transformed API development by enabling clients to request exactly the data they need, reducing over-fetching and under-fetching that plague traditional REST APIs. Since its public release by Facebook in 2015, GraphQL has gained widespread adoption across organizations of all sizes, from startups to enterprises. However, building a well-designed GraphQL API requires careful consideration of schema design, performance optimization, security, and maintainability.

This comprehensive guide explores GraphQL API design best practices, covering schema design principles, performance optimization techniques, security considerations, versioning strategies, and implementation approaches. Whether you’re building your first GraphQL API or looking to improve existing implementations, these insights will help you create flexible, efficient, and maintainable GraphQL APIs that deliver an exceptional developer experience.

File I/O in Rust: Reading and Writing Files Safely and Efficiently

Fri, 25 Apr 2025 08:00:00 +0400

File input and output (I/O) operations are fundamental to many applications, from configuration management to data processing. Rust’s approach to file I/O combines safety, performance, and ergonomics, providing powerful abstractions that prevent common errors while maintaining fine-grained control when needed. Unlike languages with implicit error handling or those that ignore potential failures, Rust’s type system ensures that file operations are handled correctly, making your code more robust and reliable.

In this comprehensive guide, we’ll explore Rust’s file I/O capabilities, from basic reading and writing to advanced techniques like memory mapping and asynchronous I/O. You’ll learn how to work with files efficiently, handle errors gracefully, and choose the right approach for different scenarios. By the end, you’ll have a solid understanding of how to perform file operations in Rust that are both safe and performant.

Kubernetes Advanced Deployment Strategies: Beyond Rolling Updates

Tue, 22 Apr 2025 08:00:00 +0400

Kubernetes has revolutionized how we deploy and manage containerized applications, with its built-in rolling update strategy providing a solid foundation for zero-downtime deployments. However, as applications grow in complexity and criticality, more sophisticated deployment strategies become necessary to minimize risk, validate changes in production, and respond quickly to issues.

This comprehensive guide explores advanced deployment strategies in Kubernetes that go beyond basic rolling updates. We’ll cover blue-green deployments, canary releases, A/B testing, and progressive delivery patterns, with practical examples and implementation guidance. Whether you’re looking to reduce deployment risk, test features with real users, or build a fully automated progressive delivery pipeline, this guide will help you implement the right strategy for your needs.

Security in Distributed Systems: Challenges and Best Practices

Tue, 22 Apr 2025 08:00:00 +0400

Security in distributed systems presents unique challenges that go beyond traditional application security. With components spread across multiple machines, networks, and potentially different trust domains, the attack surface expands dramatically. Each communication channel, data store, and service becomes a potential entry point for attackers. As organizations increasingly adopt distributed architectures, understanding how to secure these complex systems has become a critical concern.

This article explores the key security challenges in distributed systems and provides practical strategies and best practices to address them effectively.

Kubernetes Networking: Advanced Cluster Communication

Mon, 21 Apr 2025 00:00:00 +0000

Master Kubernetes networking including CNI.

Introduction and Setup

Kubernetes networking has a reputation for being complex, and honestly, that reputation is well-deserved. The challenge isn’t that the concepts are inherently difficult—it’s that they’re completely different from traditional networking. If you’re coming from a world of VLANs, subnets, and static IP addresses, Kubernetes networking requires a fundamental shift in thinking.

The good news is that once you understand the core principles, Kubernetes networking is actually quite elegant. It’s dynamic, software-defined, and surprisingly simple—once you stop fighting it and start working with its design philosophy.

AI Governance Frameworks: Building Responsible AI Systems

Fri, 18 Apr 2025 08:00:00 +0400

As artificial intelligence becomes increasingly integrated into critical business systems and decision-making processes, organizations face growing pressure to ensure their AI systems are developed and deployed responsibly. AI governance frameworks provide structured approaches to managing AI risks, ensuring ethical compliance, and maintaining regulatory alignment. Without proper governance, organizations risk developing AI systems that make biased decisions, violate privacy, lack transparency, or create other unintended consequences.

This comprehensive guide explores AI governance frameworks, covering risk management, ethical principles, regulatory compliance, and best practices. Whether you’re just beginning to implement AI or looking to enhance governance of existing AI systems, these insights will help you build more responsible, trustworthy, and compliant AI capabilities.

Rust's Standard Library: Essential Tools for Every Project

Tue, 15 Apr 2025 08:00:00 +0400

Rust’s standard library is a carefully curated collection of core components that provide essential functionality for almost every Rust program. Unlike some languages that include “batteries” for nearly every use case, Rust’s standard library is intentionally focused, offering only the most fundamental tools while leaving more specialized functionality to the crate ecosystem. This design philosophy ensures that the standard library remains lean, well-maintained, and suitable for a wide range of environments, from embedded systems to web servers.

Kubernetes Security: Cluster and Workload Protection

Tue, 15 Apr 2025 00:00:00 +0000

Security in Kubernetes isn’t just about locking down your cluster—it’s about building a defense-in-depth strategy that protects your workloads, data, and infrastructure while maintaining operational efficiency. This guide takes you through the essential security practices that separate production-ready clusters from development environments.

Security Foundations

Kubernetes security isn’t something you can add as an afterthought—it needs to be designed into your cluster architecture from the beginning. The difference between a secure cluster and a vulnerable one often comes down to understanding the fundamental security model and implementing proper controls at every layer.

Quantum Computing in Distributed Systems: Preparing for the Quantum Future

Thu, 10 Apr 2025 08:00:00 +0400

Quantum computing represents one of the most significant technological revolutions on the horizon, with the potential to transform how we approach complex computational problems. As quantum computers continue to advance, their integration with distributed systems will create new possibilities and challenges for system architects and developers. While fully fault-tolerant quantum computers are still developing, organizations should begin preparing for the quantum future today.

This article explores the intersection of quantum computing and distributed systems, examining how quantum technologies will impact distributed architectures and providing practical guidance on preparing for the quantum advantage.

Building Fault-Tolerant Distributed Systems: Strategies and Patterns

Sat, 05 Apr 2025 08:00:00 +0400

In distributed systems, failures are not just possible—they’re inevitable. Networks partition, servers crash, disks fail, and software bugs manifest in production. Building systems that can withstand these failures while maintaining acceptable service levels is the essence of fault tolerance. As distributed architectures become increasingly complex, mastering fault tolerance has never been more critical.

This article explores strategies, patterns, and practical techniques for building fault-tolerant distributed systems that can gracefully handle failures without catastrophic service disruptions.

Macros in Rust: Metaprogramming Made Simple

Sat, 05 Apr 2025 08:00:00 +0400

Macros are one of Rust’s most powerful features, enabling metaprogramming—code that writes code. Unlike macros in C and C++, which are simple text substitution mechanisms, Rust’s macros are hygienic and operate on the abstract syntax tree (AST), making them both powerful and safe. They allow you to extend the language, reduce boilerplate, create domain-specific languages, and implement compile-time code generation without sacrificing Rust’s safety guarantees.

In this comprehensive guide, we’ll explore Rust’s macro system in depth, from basic declarative macros to advanced procedural macros. You’ll learn how macros work, when to use them, and how to write your own macros to solve real-world problems. By the end, you’ll have a solid understanding of how to leverage Rust’s macro system to write more expressive, maintainable, and DRY (Don’t Repeat Yourself) code.

API Security Best Practices: Protecting Your Digital Interfaces

Tue, 01 Apr 2025 08:00:00 +0400

As organizations increasingly expose their services and data through APIs, these interfaces have become prime targets for attackers. According to recent studies, API attacks have grown by over 300% in the past two years, with the average organization experiencing dozens of API security incidents annually. The consequences of API breaches can be severe, ranging from data theft and service disruption to regulatory penalties and reputational damage.

This comprehensive guide explores API security best practices, covering authentication, authorization, encryption, rate limiting, input validation, and monitoring. Whether you’re building new APIs or securing existing ones, these insights will help you implement robust protection against common vulnerabilities and attacks, ensuring your digital interfaces remain secure, reliable, and compliant with regulatory requirements.

Rust's Memory Safety Guarantees: How the Compiler Protects Your Code

Sat, 29 Mar 2025 08:00:00 +0400

Memory-related bugs are among the most pernicious issues in software development. Buffer overflows, use-after-free errors, double frees, and data races have plagued systems programming for decades, leading to security vulnerabilities, crashes, and unpredictable behavior. Traditional approaches to solving these problems involve either manual memory management (prone to human error) or garbage collection (which introduces runtime overhead and unpredictable pauses).

Rust takes a revolutionary approach to memory safety by enforcing strict rules at compile time through its ownership system, borrow checker, and type system. This approach ensures memory safety without garbage collection, combining the performance of languages like C and C++ with the safety guarantees typically associated with higher-level languages.

LLM Production Deployment: Architectures, Strategies, and Best Practices

Tue, 25 Mar 2025 08:00:00 +0400

Large Language Models (LLMs) have revolutionized natural language processing and AI applications, enabling capabilities that were previously impossible. However, deploying these powerful models in production environments presents unique challenges due to their size, computational requirements, and the complexity of the systems needed to serve them efficiently.

This comprehensive guide explores the architectures, strategies, and best practices for deploying LLMs in production. Whether you’re working with open-source models like Llama 2 or Mistral, fine-tuned variants, or commercial APIs like OpenAI’s GPT-4, this guide will help you navigate the complexities of building robust, scalable, and cost-effective LLM-powered applications.

Rust for Robotics in 2025: Libraries, Tools, and Best Practices

Tue, 25 Mar 2025 08:00:00 +0400

Robotics development presents unique challenges that demand high performance, reliability, and safety guarantees. From industrial automation and autonomous vehicles to consumer robots and drones, these systems must interact with the physical world in real-time while ensuring predictable behavior. Rust, with its combination of performance comparable to C/C++ and memory safety guarantees without garbage collection, has emerged as an excellent choice for robotics development.

In this comprehensive guide, we’ll explore Rust’s ecosystem for robotics as it stands in early 2025. We’ll examine the libraries, frameworks, and tools that have matured over the years, providing developers with robust building blocks for creating efficient and reliable robotic systems. Whether you’re building industrial robots, autonomous drones, or experimental platforms, this guide will help you navigate the rich landscape of Rust’s robotics ecosystem.

Concurrency in Rust: Fearless Parallelism

Sat, 22 Mar 2025 08:00:00 +0400

Concurrency is notoriously difficult to get right. Race conditions, deadlocks, and other concurrency bugs are among the most insidious issues in software development, often manifesting only under specific timing conditions that are hard to reproduce and debug. Rust tackles this challenge head-on with a concurrency model that leverages the type system and ownership rules to prevent data races and other concurrency errors at compile time.

In this comprehensive guide, we’ll explore Rust’s approach to concurrency, from basic threads to advanced asynchronous programming. You’ll learn how Rust’s ownership system enables “fearless concurrency”—the ability to write concurrent code with confidence that the compiler will catch common mistakes before they become runtime bugs. By the end, you’ll have a solid understanding of how to build efficient, safe concurrent applications in Rust.

Case Study: How We Cut Cloud Costs by 30% Without Sacrificing Performance

Sat, 15 Mar 2025 08:00:00 +0400

Cloud cost optimization is a critical concern for organizations of all sizes, but particularly for growing companies that experience the shock of rapidly escalating cloud bills as they scale. At Ataiva, we recently worked with TechNova, a mid-sized SaaS company experiencing this exact challenge. Their monthly AWS bill had grown from $50,000 to over $200,000 in just 18 months as their customer base expanded, putting significant pressure on margins and raising concerns among investors.

Lifetimes in Rust: Managing References Safely

Sat, 15 Mar 2025 08:00:00 +0400

Lifetimes are one of Rust’s most distinctive and initially challenging features. While other aspects of Rust’s ownership system deal with who owns a value, lifetimes address how long references to that value remain valid. This mechanism ensures memory safety without a garbage collector by validating at compile time that no reference outlives the data it points to—a common source of bugs in languages like C and C++.

In this comprehensive guide, we’ll explore Rust’s lifetime system in depth, from basic concepts to advanced patterns. You’ll learn how lifetimes work, when and how to use lifetime annotations, and techniques for handling complex borrowing scenarios. By the end, you’ll have a solid understanding of how lifetimes contribute to Rust’s memory safety guarantees and how to leverage them effectively in your code.

Rust for Computer Vision in 2025: Libraries, Tools, and Best Practices

Sat, 15 Mar 2025 08:00:00 +0400

Computer vision and image processing applications demand high performance, reliability, and often real-time capabilities. From autonomous vehicles and robotics to augmented reality and medical imaging, these systems process enormous amounts of visual data and must do so efficiently and safely. Rust, with its combination of performance comparable to C/C++ and memory safety guarantees without garbage collection, has emerged as an excellent choice for computer vision development.

In this comprehensive guide, we’ll explore Rust’s ecosystem for computer vision and image processing as it stands in early 2025. We’ll examine the libraries, frameworks, and tools that have matured over the years, providing developers with robust building blocks for creating efficient and reliable vision applications. Whether you’re building real-time video processing systems, image analysis tools, or integrating computer vision with machine learning, this guide will help you navigate the rich landscape of Rust’s computer vision ecosystem.

Kubernetes Operators: Custom Resource Management

Sat, 15 Mar 2025 00:00:00 +0000

Build and deploy Kubernetes operators for automated application management.

Introduction and Setup

When I first started working with Kubernetes, I quickly realized that managing complex applications required more than just deploying pods and services. That’s where operators come in - they’re like having an experienced system administrator encoded in software, continuously managing your applications with domain-specific knowledge.

Understanding Kubernetes Operators

Operators extend Kubernetes by combining Custom Resource Definitions (CRDs) with controllers that understand how to manage specific applications. I’ve seen teams struggle with manual database backups, complex scaling decisions, and application lifecycle management. Operators solve these problems by automating operational tasks that would otherwise require human intervention.

Blockchain in Enterprise Distributed Systems: Beyond Cryptocurrencies

Mon, 10 Mar 2025 08:00:00 +0400

While blockchain technology first gained prominence as the foundation for cryptocurrencies like Bitcoin, its potential applications extend far beyond digital currencies. At its core, blockchain is a distributed ledger technology that provides a secure, transparent, and immutable record of transactions across a decentralized network. These properties make it particularly valuable for enterprise distributed systems that require trust, transparency, and data integrity across multiple parties.

This article explores practical enterprise applications of blockchain technology in distributed systems, examining implementation patterns, challenges, and best practices for organizations looking to leverage this transformative technology.

Infrastructure as Code Best Practices: Beyond the Basics

Mon, 10 Mar 2025 08:00:00 +0400

Infrastructure as Code (IaC) has revolutionized how organizations manage their cloud resources, enabling teams to provision and manage infrastructure through machine-readable definition files rather than manual processes. While most teams have adopted basic IaC practices, many struggle to implement the advanced patterns and workflows that lead to truly maintainable, secure, and efficient infrastructure management.

This comprehensive guide explores advanced Infrastructure as Code best practices that go beyond the basics. We’ll cover strategies for testing, security, modularity, team workflows, and more—all designed to help you elevate your IaC implementation from functional to exceptional. Whether you’re using Terraform, CloudFormation, Pulumi, or another IaC tool, these principles will help you build more robust infrastructure management capabilities.

Distributed Caching Strategies for High-Performance Applications

Fri, 07 Mar 2025 08:00:00 +0400

In today’s digital landscape, where milliseconds can make the difference between user engagement and abandonment, caching has become an indispensable technique for building high-performance applications. As systems scale and distribute across multiple servers or regions, simple in-memory caching is no longer sufficient. This is where distributed caching comes into play—providing a shared cache that spans multiple servers, enabling consistent performance across distributed applications.

This article explores distributed caching strategies, patterns, and implementations that can help you build faster, more scalable applications while reducing the load on your databases and backend services.

Rust for Audio Programming in 2025: Libraries, Tools, and Best Practices

Wed, 05 Mar 2025 08:00:00 +0400

Audio programming presents unique challenges that demand both high performance and reliability. From real-time digital signal processing to music creation tools, audio applications require low latency, predictable memory usage, and freedom from unexpected crashes or glitches. Rust, with its combination of performance comparable to C/C++ and memory safety guarantees without garbage collection, has emerged as an excellent choice for audio development.

In this comprehensive guide, we’ll explore Rust’s ecosystem for audio programming as it stands in early 2025. We’ll examine the libraries, frameworks, and tools that have matured over the years, providing developers with robust building blocks for creating efficient and reliable audio applications. Whether you’re building digital audio workstations, audio plugins, embedded audio devices, or game audio engines, this guide will help you navigate the rich landscape of Rust’s audio programming ecosystem.

Traits in Rust: Interfaces with Superpowers

Wed, 05 Mar 2025 08:00:00 +0400

In object-oriented programming, interfaces define a contract that implementing classes must fulfill. Rust’s trait system serves a similar purpose but goes far beyond traditional interfaces, offering a powerful mechanism for defining shared behavior, enabling polymorphism, and creating flexible abstractions—all while maintaining Rust’s guarantees of memory safety and performance.

Traits are one of Rust’s most distinctive and powerful features, enabling code reuse without inheritance and polymorphism without runtime overhead. In this comprehensive guide, we’ll explore Rust’s trait system in depth, from basic usage to advanced patterns. You’ll learn how to define and implement traits, use trait bounds, work with trait objects, and leverage traits to write generic code that is both flexible and efficient.

Kubernetes Configuration Management

Sat, 01 Mar 2025 00:00:00 +0000

Master Kubernetes configuration with ConfigMaps.

Introduction and Setup

Configuration management in Kubernetes nearly broke me when I first started trying to use it. I spent three days debugging why my application couldn’t connect to the database, only to discover I’d misspelled “postgres” as “postgress” in a ConfigMap. That typo taught me more about Kubernetes configuration than any documentation ever could.

The frustrating truth about Kubernetes configuration is that it looks simple until you need it to work reliably across environments. ConfigMaps and Secrets seem straightforward, but managing configuration at scale requires patterns that aren’t obvious from the basic examples.

Working with Structs and Enums in Rust: Building Robust Data Models

Fri, 28 Feb 2025 08:00:00 +0400

Data modeling is at the heart of software development, and the tools a language provides for representing data significantly impact code quality, maintainability, and correctness. Rust offers two powerful constructs for modeling data: structs and enums. These complementary tools allow developers to express complex data relationships with precision while leveraging Rust’s type system to prevent entire categories of bugs at compile time.

In this comprehensive guide, we’ll explore Rust’s structs and enums in depth, from basic usage to advanced patterns. You’ll learn how to create flexible, type-safe data models that express your domain concepts clearly and leverage the compiler to catch errors early. By the end, you’ll have a solid understanding of when and how to use each construct effectively in your Rust projects.

SLO and SLI Implementation Guide: Building Reliable Services

Tue, 25 Feb 2025 08:00:00 +0400

In today’s digital landscape, reliability has become a critical differentiator for services and products. Users expect systems to be available, responsive, and correct—all the time. However, pursuing 100% reliability is not only prohibitively expensive but often unnecessary. This is where Service Level Objectives (SLOs) and Service Level Indicators (SLIs) come in, providing a framework to define, measure, and maintain appropriate reliability targets that balance user expectations with engineering costs.

This comprehensive guide explores the practical aspects of implementing SLOs and SLIs in your organization. We’ll cover everything from selecting the right metrics to building the technical infrastructure needed to track them, and establishing the processes to act on the resulting data. Whether you’re just starting with reliability engineering or looking to refine your existing practices, this guide provides actionable insights to help you build more reliable services.

Pattern Matching in Rust: Powerful, Expressive, and Safe

Sat, 15 Feb 2025 08:00:00 +0400

Pattern matching stands as one of Rust’s most powerful and distinctive features, elevating it beyond a mere control flow mechanism to a fundamental aspect of the language’s design philosophy. Unlike the simple switch statements found in many languages, Rust’s pattern matching system provides a rich, expressive way to destructure complex data types, handle multiple conditions, and ensure exhaustive checking of all possible cases. This combination of power and safety makes pattern matching an essential tool in every Rust programmer’s toolkit.

Rust's Blockchain Development Ecosystem in 2025

Sat, 15 Feb 2025 08:00:00 +0400

Blockchain technology has evolved significantly since the introduction of Bitcoin in 2009, expanding beyond cryptocurrencies to encompass smart contracts, decentralized finance (DeFi), non-fungible tokens (NFTs), and various forms of decentralized applications (dApps). As blockchain systems have grown more complex and demanding, the need for programming languages that prioritize safety, performance, and reliability has become increasingly apparent. Rust, with its focus on memory safety without sacrificing performance, has emerged as a leading language for blockchain development.

Scaling Startups with Cloud Best Practices

Sat, 15 Feb 2025 08:00:00 +0400

Scaling a startup’s technical infrastructure is one of the most challenging aspects of company growth. As user numbers increase, feature sets expand, and market demands evolve, the technology decisions made in the early days are put to the test. Cloud computing has revolutionized how startups scale, offering unprecedented flexibility and power—but also introducing complexity and potential pitfalls.

This comprehensive guide explores cloud best practices for scaling startups, covering everything from architectural patterns and cost optimization to security, DevOps, and organizational strategies. Whether you’re experiencing hypergrowth or planning for sustainable expansion, these practices will help you build a robust, efficient, and adaptable cloud infrastructure that supports your business goals.

MLOps Pipeline Architecture: Building Production-Ready ML Systems

Wed, 12 Feb 2025 08:00:00 +0400

Machine learning has moved beyond research and experimentation to become a critical component of many production systems. However, successfully deploying and maintaining ML models in production requires more than just good data science—it demands robust engineering practices, automated pipelines, and governance frameworks. This is where MLOps (Machine Learning Operations) comes in, bridging the gap between ML development and operational excellence.

This comprehensive guide explores the architecture of production-grade MLOps pipelines, covering everything from data preparation to model monitoring. Whether you’re building your first ML system or looking to improve your existing ML operations, this guide provides practical insights and implementation patterns for creating reliable, scalable, and governable machine learning systems.

Error Handling in Rust: Mastering Result and Option Types

Wed, 05 Feb 2025 08:00:00 +0400

Error handling is a critical aspect of writing reliable software, yet it’s often treated as an afterthought in many programming languages. Some languages rely on exceptions that can be easily overlooked, while others use error codes that can be ignored. Rust takes a fundamentally different approach by making error handling explicit through its type system, primarily using the Result and Option types. This approach ensures that errors are handled deliberately rather than by accident or omission. This error handling system works hand-in-hand with Rust’s ownership system to create safe, reliable code.

Rust's Distributed Systems Ecosystem in 2025

Wed, 05 Feb 2025 08:00:00 +0400

Distributed systems have become the backbone of modern computing infrastructure, powering everything from cloud services and microservices architectures to blockchain networks and IoT platforms. Building these systems presents unique challenges: network partitions, partial failures, consistency issues, and the inherent complexity of coordinating multiple nodes. Rust, with its focus on reliability, performance, and fine-grained control, has emerged as an excellent language for tackling these challenges.

In this comprehensive guide, we’ll explore Rust’s ecosystem for building distributed systems as it stands in early 2025. We’ll examine the libraries, frameworks, and tools that have matured over the years, providing developers with robust building blocks for creating reliable and scalable distributed applications. Whether you’re building a microservices architecture, a peer-to-peer network, or a distributed database, this guide will help you navigate the rich landscape of Rust’s distributed systems ecosystem.

Rust's Type System: A Deep Dive into Safety and Expressiveness

Fri, 31 Jan 2025 08:00:00 +0400

Rust’s type system stands as one of its most powerful features, combining the expressiveness of modern languages with the safety guarantees that systems programming demands. Unlike dynamically typed languages that defer type checking to runtime, or statically typed languages with escape hatches that can lead to undefined behavior, Rust’s type system is designed to catch errors at compile time while remaining flexible enough for real-world programming challenges.

In this comprehensive exploration, we’ll dive deep into Rust’s type system, examining how it balances safety and expressiveness. We’ll cover everything from basic types to advanced type-level programming techniques, providing you with the knowledge to leverage Rust’s type system to its fullest potential. By the end, you’ll understand why Rust’s approach to types is a game-changer for building reliable software.

Borrowing and References in Rust: The Art of Safe Memory Sharing

Sat, 25 Jan 2025 08:00:00 +0400

In our previous exploration of Rust’s ownership system, we established how Rust manages memory through a set of compile-time rules that track the ownership of values. While ownership provides the foundation for Rust’s memory safety guarantees, constantly transferring ownership would make code unnecessarily complex and inefficient. This is where Rust’s borrowing system comes into play—a sophisticated mechanism that allows you to use values without transferring ownership.

Borrowing, implemented through references, is what makes Rust’s ownership model practical for everyday programming. It enables multiple parts of your code to access the same data concurrently while still maintaining Rust’s strict safety guarantees. In this comprehensive guide, we’ll dive deep into Rust’s borrowing system, explore the nuances of references, and uncover advanced patterns that will elevate your Rust programming skills.

Implementing Distributed Tracing: A Practical Guide for Modern Applications

Mon, 20 Jan 2025 08:00:00 +0400

In today’s world of distributed systems and microservices architectures, understanding the flow of requests across dozens or even hundreds of services has become increasingly challenging. When a user experiences a slow response or an error, pinpointing the root cause can feel like searching for a needle in a haystack. This is where distributed tracing comes in—providing a powerful lens through which we can observe, understand, and optimize our distributed applications.

Rust Security Features and Best Practices in 2025

Mon, 20 Jan 2025 08:00:00 +0400

Security has become a paramount concern in software development, with vulnerabilities and exploits causing billions in damages annually. As systems become more interconnected and complex, the need for programming languages that prioritize security by design has never been greater. Rust, with its focus on memory safety without sacrificing performance, has positioned itself as a leading language for security-critical applications. By eliminating entire classes of bugs at compile time, Rust provides developers with powerful tools to write secure code from the ground up.

Kubernetes Pod Security Policies: Best Practices for Cluster Protection

Wed, 15 Jan 2025 08:00:00 +0400

As Kubernetes adoption continues to grow across organizations of all sizes, securing containerized workloads has become a critical concern. Pod Security Policies (PSPs) and their successor, Pod Security Admission, represent Kubernetes’ native approach to enforcing security best practices at the pod level. By controlling the security-sensitive aspects of pod specifications, these mechanisms help prevent privilege escalation and limit the potential damage from container-based attacks.

This comprehensive guide explores how to implement effective pod security controls in Kubernetes, covering both the legacy Pod Security Policies and the newer Pod Security Standards and Admission Controller. You’ll learn practical strategies for balancing security with operational requirements, implementing defense in depth, and addressing common security challenges in Kubernetes environments.

Understanding Rust's Ownership System: The Key to Memory Safety

Wed, 15 Jan 2025 08:00:00 +0400

Rust’s ownership system stands as one of the language’s most revolutionary contributions to systems programming. While other languages rely on garbage collection or manual memory management, Rust introduces a third approach: ownership with borrowing. This system enables Rust to guarantee memory safety at compile time without runtime overhead, preventing entire categories of bugs that plague other languages. For developers coming from languages like C++, Java, or Python, understanding ownership is the key to unlocking Rust’s full potential. This ownership system is also a key part of Rust’s security features and best practices and works hand-in-hand with Rust’s error handling system.

Distributed Systems Fundamentals: Core Concepts Every Developer Should Know

Tue, 07 Jan 2025 08:00:00 +0400

In today’s interconnected world, distributed systems have become the backbone of modern software architecture. From global e-commerce platforms to real-time collaboration tools, distributed systems enable applications to scale beyond the confines of a single machine, providing resilience, performance, and global reach. However, with these benefits come significant challenges that every developer must understand to build effective distributed applications.

This article explores the fundamental concepts of distributed systems, providing a solid foundation for developers looking to navigate this complex but essential domain. We’ll examine the core principles, common challenges, and practical approaches that form the basis of distributed system design.

Getting Started with Rust: A Comprehensive Installation and Setup Guide

Sun, 05 Jan 2025 08:00:00 +0400

Rust has emerged as one of the most promising programming languages of the decade, offering an unparalleled combination of performance, reliability, and productivity. Whether you’re a seasoned developer looking to expand your toolkit or a newcomer to systems programming, setting up Rust correctly is your first step toward mastering this powerful language. This comprehensive guide will walk you through the installation process across different operating systems, help you configure your development environment, and introduce you to essential tools in the Rust ecosystem.

Rust Interoperability: Seamlessly Working with Other Languages in 2025

Sun, 05 Jan 2025 08:00:00 +0400

In today’s complex software landscape, few applications are built using a single programming language. Different languages offer different strengths, and existing codebases represent significant investments that can’t be rewritten overnight. This reality makes language interoperability—the ability for code written in different languages to work together seamlessly—a critical feature for any modern programming language. Rust, with its focus on safety, performance, and practicality, has developed robust interoperability capabilities that allow it to integrate smoothly with a wide range of other languages.

Rust's unwrap: Unlocking Its Potential and Avoiding Pitfalls

Mon, 30 Dec 2024 06:00:00 +0400

Learn how to effectively use Rust’s unwrap method, including its benefits, risks, and safer alternatives, in this comprehensive guide. At the heart of its error-handling mechanism lie the Option and Result types, which provide developers with tools to explicitly manage the presence or absence of values and handle potential errors in computations. However, there exists a method—unwrap—that offers a shortcut for extracting values from these types. While powerful, its misuse can lead to unexpected panics, making it a topic of both fascination and caution among Rustaceans.

Optimizing the Two Sum Problem: Techniques, Trade-offs, and Performance

Fri, 13 Dec 2024 06:00:00 +0400

The Problem Statement

One of the classic algorithm problems frequently encountered in interviews is the Two Sum problem. It challenges you to find two indices in an array such that the sum of the elements at these indices equals a given target. It seems simple, but the real depth lies in optimizing its solution.

There is this common programming question that goes something like this:

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

Chaos Engineering Practices: Building Resilient Systems Through Controlled Failure

Tue, 10 Dec 2024 08:00:00 +0400

In today’s complex distributed systems, failures are inevitable. Networks partition, services crash, dependencies slow down, and hardware fails. Traditional testing approaches often fall short in identifying how these systems behave under unexpected conditions. Chaos Engineering has emerged as a disciplined approach to identify weaknesses in distributed systems by deliberately injecting failures in a controlled manner.

This comprehensive guide explores chaos engineering principles, tools, implementation strategies, and real-world examples. Whether you’re just starting your reliability journey or looking to enhance your existing practices, these approaches will help you build more resilient systems that can withstand the turbulence of production environments.

Low-Code/No-Code Platforms: Democratizing Application Development

Fri, 15 Nov 2024 08:00:00 +0400

The demand for software applications continues to outpace the availability of professional developers, creating significant backlogs and slowing digital transformation initiatives. Low-code and no-code development platforms have emerged as powerful solutions to this challenge, enabling both professional developers and business users to build applications with minimal traditional coding. By abstracting away complex technical details through visual interfaces and pre-built components, these platforms democratize application development and accelerate delivery.

This comprehensive guide explores low-code and no-code platforms, covering their capabilities, use cases, implementation strategies, governance, and best practices. Whether you’re evaluating these platforms for your organization or looking to optimize your existing implementation, these insights will help you leverage low-code/no-code approaches to drive innovation while maintaining enterprise standards.

Kubernetes Fundamentals: Container Orchestration Basics

Sun, 10 Nov 2024 00:00:00 +0000

Learn the core concepts and practical skills needed to deploy, manage, and scale containerized applications using Kubernetes.

Introduction and Setup

Introduction to Kubernetes

Container orchestration sounds complicated, but the problem it solves is simple: how do you run dozens or hundreds of containers across multiple servers without losing your sanity? Docker works great for single containers, but when you need to manage entire applications with databases, web servers, and background workers, you quickly realize you need something more sophisticated.

Cloud Cost Optimization: Maximizing ROI

Wed, 06 Nov 2024 00:00:00 +0000

Master cloud cost optimization strategies.

Understanding Cloud Waste: The Hidden Cost of Convenience

Before diving into solutions, it’s important to understand the common sources of cloud waste:

1. Idle Resources

Resources that are provisioned but not actively used:

Running instances with low CPU utilization
Provisioned databases with minimal connections
Load balancers routing traffic to a single instance

2. Overprovisioned Resources

Resources allocated beyond actual requirements:

Instances with more CPU/memory than needed
Databases with excessive provisioned IOPS
Oversized storage volumes with low utilization

3. Orphaned Resources

Resources that are no longer needed but still incurring costs:

Cloud Performance Tuning: Optimization Strategies

Wed, 06 Nov 2024 00:00:00 +0000

Optimize cloud application performance with advanced tuning techniques.

Introduction to Cloud Performance Tuning

Working with hundreds of customer applications has taught me that performance problems follow predictable patterns. Whether it’s a startup scaling their first viral app or an enterprise migrating legacy systems, the same fundamental issues appear repeatedly: chatty applications making too many API calls, databases overwhelmed by inefficient queries, and auto-scaling policies that react too slowly to traffic spikes.

Observability Platforms Comparison: Choosing the Right Monitoring Solution

Tue, 05 Nov 2024 08:00:00 +0400

As systems grow more complex and distributed, traditional monitoring approaches fall short. Modern observability platforms have emerged to provide deeper insights into system behavior, performance, and health. However, choosing the right observability solution for your organization can be challenging given the wide range of options available, each with different strengths, architectures, and pricing models.

This comprehensive guide compares leading observability platforms including Prometheus, Grafana, Datadog, New Relic, Elastic Observability, and Dynatrace. We’ll examine their features, architectures, pricing models, and ideal use cases to help you make an informed decision for your specific needs.

Microservices vs Monoliths: Architecture Patterns

Tue, 05 Nov 2024 00:00:00 +0000

Understand the trade-offs between microservices and monolithic architectures.

Understanding the Architectural Patterns

Before diving into comparisons, let’s establish a clear understanding of each architectural pattern.

Monolithic Architecture

A monolithic architecture is a traditional unified model where all components of an application are interconnected and interdependent, functioning as a single unit.

Key Characteristics:

Single Codebase: All functionality exists in a single codebase
Shared Database: Components typically share a single database
Unified Deployment: The entire application is deployed as a single unit
Tightly Coupled: Components are interconnected and interdependent
Vertical Scaling: Typically scaled by adding more resources to a single server

Example Structure of a Monolithic E-commerce Application:

How to Migrate Docker Repositories to a New DockerHub Username

Mon, 04 Nov 2024 06:00:00 +0400

If you’ve ever tried to rename your DockerHub username, you know there’s no direct way to do it. For many users, creating a new DockerHub account and transferring all their repositories is the best option. This guide walks you through automating the process of migrating all Docker images from an old username to a new one. We’ll share a complete shell script, so you don’t have to manually tag and push each image, saving you time and effort.

Python 3.13 No-GIL Mode: How to Unlock True Multi-Threading and Boost Performance

Fri, 01 Nov 2024 06:00:00 +0400

Python 3.13 has quietly introduced a game-changing experimental feature: no-GIL mode! For years, the Global Interpreter Lock (GIL) has been a barrier to true parallelism in Python, limiting Python threads to one at a time. But with Python 3.13, you can now compile Python to run without the GIL, allowing Python threads to fully utilize multiple cores. Let’s dive into why this matters, how to try it out, and what kinds of performance gains you might see.

API-First Development: Building Scalable Interfaces

Fri, 25 Oct 2024 00:00:00 +0000

Master API-first development methodologies.

API-First Fundamentals

Core Principles and Benefits

Understanding the foundational concepts:

API-First Definition:

Designing APIs before implementing applications
Treating APIs as first-class products
Focusing on consumer needs and use cases
Establishing clear contracts between systems
Enabling parallel development workflows
Creating consistent, reusable interfaces

Traditional vs. API-First Approach:

Traditional Development:
Requirements → Application Development → API Creation → Integration → Deployment

API-First Development:
Requirements → API Design → API Contract → Parallel Development → Integration → Deployment
                                            ├─ Frontend Development
                                            ├─ Backend Implementation
                                            └─ Consumer Integration

Key Benefits:

Kubernetes vs Serverless: Architecture Decision Guide

Thu, 17 Oct 2024 00:00:00 +0000

Compare Kubernetes and serverless architectures.

Understanding the Core Concepts

Before diving into comparisons, let’s establish a clear understanding of each approach.

Kubernetes: Container Orchestration at Scale

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.

Key Components:

Nodes: Physical or virtual machines that form the Kubernetes cluster
Pods: The smallest deployable units, containing one or more containers
Deployments: Controllers that manage pod replication and updates
Services: Abstractions that define how to access pods
ConfigMaps and Secrets: Resources for configuration and sensitive data
Namespaces: Virtual clusters for resource isolation
Ingress: Rules for external access to services

Core Capabilities:

Benefits of Cloud-Native Applications: Building for the Modern Infrastructure

Tue, 15 Oct 2024 06:00:00 +0400

The landscape of application development and deployment has undergone a profound transformation over the past decade. Traditional monolithic applications hosted on physical servers have given way to cloud-native applications designed specifically to leverage the capabilities of modern cloud infrastructure. This shift isn’t merely a change in hosting environment—it represents a fundamental reimagining of how applications are built, deployed, and operated.

Cloud-native applications are specifically designed to thrive in cloud environments, embracing principles like containerization, microservices architecture, declarative APIs, and immutable infrastructure. These applications are built to harness the full potential of cloud platforms, delivering unprecedented levels of scalability, resilience, and agility.

Event-Driven Architecture: Building Reactive Systems

Tue, 15 Oct 2024 00:00:00 +0000

Design and implement event-driven architectures using messaging patterns.

Understanding Event-Driven Architecture

Before diving into specific patterns, let’s establish a clear understanding of what constitutes an event-driven architecture.

What is an Event?

An event is a record of something that has happened—a fact. Events are immutable, meaning once an event has occurred, it cannot be changed or deleted. Events typically include:

A unique identifier
Event type or name
Timestamp
Payload (the data describing what happened)
Metadata (additional contextual information)

Examples of events include:

Rust Performance Optimization: High-Performance Programming

Sun, 06 Oct 2024 00:00:00 +0000

Optimize Rust applications for maximum performance with profiling.

Performance Optimization Fundamentals

Before diving into specific techniques, let’s establish some fundamental principles:

The Optimization Process

1. Measure - Establish a baseline and identify bottlenecks
2. Analyze - Understand why the bottlenecks exist
3. Improve - Make targeted changes to address the bottlenecks
4. Verify - Measure again to confirm improvements
5. Repeat - Continue until performance goals are met

Premature Optimization

As Donald Knuth famously said, “Premature optimization is the root of all evil.” Focus on writing clear, correct code first, then optimize where necessary:

AI-Powered Distributed Systems: Architectures and Implementation Patterns

Sat, 05 Oct 2024 08:00:00 +0400

The integration of artificial intelligence (AI) with distributed systems represents one of the most significant technological advancements in recent years. As distributed systems grow in complexity, traditional management approaches struggle to keep pace. AI offers powerful capabilities to enhance these systems with self-healing, intelligent scaling, anomaly detection, and automated optimization. This convergence is creating a new generation of distributed systems that are more resilient, efficient, and adaptive than ever before.

API Security Guide: Protect Your Application from Cyber Threats

Wed, 02 Oct 2024 06:00:00 +0400

Welcome to our journey into the world of API Security, Definitions, and Meanings!

My name is Alex, and I’m a cybersecurity expert with a passion for helping individuals and organizations understand the importance of protecting their APIs. With over 10 years of experience in the field, I’ve seen firsthand how a single misconfigured API can lead to catastrophic consequences.

So, why am I so passionate about API security? Well, it all started when I was working on a project that involved developing a custom API for a client. As I delved deeper into the world of APIs, I realized just how vulnerable they were to attacks. A single malicious actor could exploit a weakness in our API and gain access to sensitive data or disrupt the entire system.

Rust Design Patterns: Idiomatic Programming

Sat, 28 Sep 2024 00:00:00 +0000

Master Rust design patterns.

Memory Management Patterns

Rust’s ownership system influences how we manage resources:

RAII (Resource Acquisition Is Initialization)

RAII is a fundamental pattern in Rust where resources are acquired during initialization and released when the object goes out of scope:

struct File {
    handle: std::fs::File,
}

impl File {
    fn new(path: &str) -> Result<Self, std::io::Error> {
        let handle = std::fs::File::open(path)?;
        Ok(File { handle })
    }
    
    fn read_to_string(&mut self) -> Result<String, std::io::Error> {
        let mut content = String::new();
        self.handle.read_to_string(&mut content)?;
        Ok(content)
    }
}

// The file is automatically closed when `file` goes out of scope
fn process_file(path: &str) -> Result<String, std::io::Error> {
    let mut file = File::new(path)?;
    file.read_to_string()
}

Drop Guard

A drop guard ensures that cleanup code runs even if a function returns early:

How to Create Your Own Programming Language

Thu, 19 Sep 2024 06:00:00 +0400

A programming language is a system of communication and computation used to control a computer. Languages allow us to write instructions in a format that computers can understand and execute.

While many popular languages like Python, Java, and JavaScript already exist, you may want to create your own for learning purposes or to solve a specific problem. Here is an overview of the key steps involved in designing a custom programming language.

Poetry vs Pip: Comparing Python Dependency Management and Packaging Tools

Fri, 13 Sep 2024 06:00:00 +0400

Poetry and Pip are two popular tools for managing Python dependencies and packaging Python projects. Both have their own sets of advantages and disadvantages. This guide will provide a technical comparison of the two tools and demonstrate why Poetry has more features and is generally preferable to Pip for most use cases.

Key Differences

Some of the key differences between Poetry and Pip include:

Dependency resolution: Poetry uses a resolver to find the best combination of package versions to meet your requirements. Pip does not do this, it just installs the latest version that matches each requirement.

Sustainable Cloud Computing for Distributed Systems

Thu, 12 Sep 2024 08:00:00 +0400

As distributed systems increasingly rely on cloud computing resources, their environmental impact has become a growing concern. The global IT industry accounts for approximately 2-3% of worldwide carbon emissions—comparable to the aviation industry—with data centers alone consuming about 1% of global electricity. With the exponential growth of distributed systems and cloud computing, implementing sustainable practices is not just an environmental imperative but also a business necessity.

This article explores practical strategies and technologies for implementing sustainable cloud computing in distributed systems, helping organizations reduce their environmental impact while maintaining performance, reliability, and cost-effectiveness.

API Design Principles: Building Interfaces That Last

Tue, 10 Sep 2024 08:00:00 +0400

Application Programming Interfaces (APIs) have become the foundation of modern software development, enabling seamless integration between systems, powering microservices architectures, and facilitating third-party ecosystems. However, designing APIs that are intuitive, efficient, secure, and able to evolve over time requires careful consideration of numerous principles and best practices.

This comprehensive guide explores API design principles that lead to robust, developer-friendly interfaces. We’ll cover RESTful design, GraphQL, versioning strategies, authentication methods, documentation approaches, and patterns for creating APIs that stand the test of time. Whether you’re building public APIs for third-party developers or internal interfaces for microservices, these principles will help you create APIs that are a joy to use and maintain.

A Complete DevOps Guide for Beginners

Thu, 05 Sep 2024 06:00:00 +0400

Are you looking to improve your software development workflow and increase efficiency? Look no further than DevOps! In this comprehensive guide, we’ll explore what DevOps means, its benefits, and how to get started with implementing it in your own organization.

Hello there! My name is Andrew, and I’m excited to share my expertise on DevOps Engineering with you. As someone who has spent years working in the field, I’ve seen firsthand how it can transform organizations and bring people together. In this guide, we’ll explore what DevOps means, its benefits, and how to get started with implementing it in your own life.

Creating a Docker Alternative in Python

Mon, 26 Aug 2024 06:00:00 +0400

Docker is a popular containerization platform that allows developers to easily package applications into lightweight containers that can run isolated on any system. Containers provide a convenient way to deploy and scale applications by bundling together all the dependencies and configurations needed to run the app.

In this guide, we will walk through how to create a simple docker alternative in Python. The goal is to build a basic container runtime that can build images, run containers, and manage containers lifecycles. While this will only cover a subset of Docker’s functionality, it will demonstrate the core concepts needed to build a container engine.

Why Different Programming Languages Need to Exist

Mon, 26 Aug 2024 06:00:00 +0400

Programming languages allow us to communicate with computers by writing code. There are hundreds of programming languages in use today, and new ones are constantly being created. But why do we need so many different languages? Here are some key reasons:

Different Levels of Abstraction

Programming languages operate at different levels of abstraction from the underlying machine code that computers understand. Lower level languages like C and Assembly provide direct access to computer hardware and memory. They require developers to manage many details but allow for precise control and high performance.

Database Scaling Strategies: From Gigabytes to Petabytes

Thu, 15 Aug 2024 08:00:00 +0400

As applications grow in popularity and data volumes expand, database performance often becomes a critical bottleneck. What worked perfectly during development or early production can quickly become inadequate as user numbers increase and data accumulates. Scaling database systems effectively requires a deep understanding of various strategies, their trade-offs, and implementation approaches.

This comprehensive guide explores database scaling strategies from vertical scaling to distributed systems, covering relational and NoSQL approaches, replication, sharding, and cloud-native solutions. Whether you’re experiencing growing pains with your current database or planning ahead for future scale, these strategies will help you build resilient, high-performance database systems that grow with your business.

Rust for Quantum Computing in 2024: Libraries, Tools, and Best Practices

Sat, 10 Aug 2024 08:00:00 +0400

Quantum computing represents one of the most exciting frontiers in computer science, promising computational capabilities that could revolutionize fields from cryptography to drug discovery. As quantum hardware continues to advance, there’s a growing need for robust software tools to bridge the gap between quantum algorithms and physical quantum processors. Rust, with its combination of performance comparable to C/C++ and memory safety guarantees without garbage collection, has emerged as an excellent choice for quantum computing development.

The Future of AI in Software Development: What to Expect in 2025

Thu, 08 Aug 2024 06:00:00 +0400

As we stand on the cusp of a new era in technology, the integration of Artificial Intelligence (AI) into software development is poised to revolutionize the way we create, maintain, and evolve digital solutions. By 2025, the landscape of software engineering is expected to undergo a dramatic transformation, with AI playing a pivotal role in every aspect of the development lifecycle. From intelligent code generation to predictive maintenance and beyond, the fusion of AI and software development promises to enhance productivity, improve code quality, and accelerate innovation at an unprecedented scale.

Learn Concurrency in Go

Mon, 22 Jul 2024 06:00:00 +0400

Concurrency in Go is one of its most powerful features, designed to make it easy to write concurrent programs. Go’s concurrency model is based on goroutines and channels, which provide a simple and efficient way to manage multiple tasks running in parallel.

Goroutines

A goroutine is a lightweight thread managed by the Go runtime. You can start a new goroutine using the go keyword followed by a function call. Goroutines run concurrently with other goroutines.

Learn Go as a DevOps Engineer

Thu, 18 Jul 2024 06:00:00 +0400

Go, also known as Golang, is an open-source programming language designed for simplicity, efficiency, and reliability. It has become increasingly popular in the DevOps community due to its powerful standard library, ease of use, and performance capabilities. This guide aims to provide DevOps engineers with a comprehensive understanding of Go, from basic syntax to advanced topics, complete with practical examples and code snippets.

1. Introduction to Go

What is Go?

Go is a statically typed, compiled programming language designed by Google. It emphasizes simplicity and efficiency, making it ideal for scalable system programming and cloud-native development.

Rust CLI Applications: Command-Line Tool Development

Mon, 15 Jul 2024 00:00:00 +0000

Build robust.

Getting Started: A Simple CLI Application

Let’s start with a basic command-line application that accepts arguments and prints output:

use std::env;

fn main() {
    // Collect command-line arguments
    let args: Vec<String> = env::args().collect();
    
    // The first argument is the program name
    println!("Program name: {}", args[0]);
    
    // Print the remaining arguments
    if args.len() > 1 {
        println!("Arguments:");
        for (i, arg) in args.iter().enumerate().skip(1) {
            println!("  {}: {}", i, arg);
        }
    } else {
        println!("No arguments provided");
    }
}

This simple example demonstrates how to access command-line arguments using the standard library. However, for more complex applications, we’ll want to use dedicated argument parsing libraries.

How to Run Technical Discovery Sessions: A Comprehensive Guide

Fri, 05 Jul 2024 08:00:00 +0400

Technical discovery sessions are the foundation of successful software projects. These structured conversations between technical teams, stakeholders, and subject matter experts uncover requirements, constraints, and context that shape the entire project lifecycle. When done well, discovery sessions align expectations, identify risks early, and create a shared understanding that guides implementation. When done poorly, they lead to misaligned expectations, missed requirements, and ultimately, project failure.

This comprehensive guide explores how to plan and facilitate effective technical discovery sessions. Whether you’re a solution architect, technical lead, or project manager, this guide provides actionable strategies for preparation, facilitation, documentation, and follow-up to ensure your discovery sessions deliver maximum value.

Secrets Management in Cloud Environments: Best Practices and Tools

Mon, 01 Jul 2024 06:00:00 +0400

In today’s cloud-native world, applications require access to numerous secrets—API keys, database credentials, encryption keys, and other sensitive information. Managing these secrets securely is one of the most critical aspects of cloud security. Poor secrets management can lead to data breaches, unauthorized access, and compliance violations that can severely impact your organization.

This comprehensive guide explores best practices, tools, and implementation strategies for effective secrets management across AWS, Azure, and Google Cloud Platform (GCP), helping you build a robust security posture for your cloud environments.

Rust Module System: Code Organization

Sat, 22 Jun 2024 00:00:00 +0000

Master Rust’s module system.

Understanding the Basics of Rust’s Module System

At its core, Rust’s module system is about organizing code and controlling visibility. Let’s start with the fundamental concepts:

Modules: Organizing Code into Logical Units

A module is a container for items such as functions, structs, traits, impl blocks, and even other modules:

// Define a module named 'geometry"
mod geometry {
    // Constants within the module
    const PI: f64 = 3.14159;
    
    // Functions within the module
    pub fn area_of_circle(radius: f64) -> f64 {
        PI * radius * radius
    }
    
    // Nested module
    pub mod shapes {
        pub struct Rectangle {
            pub width: f64,
            pub height: f64,
        }
        
        impl Rectangle {
            pub fn new(width: f64, height: f64) -> Rectangle {
                Rectangle { width, height }
            }
            
            pub fn area(&self) -> f64 {
                self.width * self.height
            }
        }
    }
}

fn main() {
    // Using items from the module
    let area = geometry::area_of_circle(5.0);
    println!("Area of circle: {}", area);
    
    let rect = geometry::shapes::Rectangle::new(10.0, 5.0);
    println!("Area of rectangle: {}", rect.area());
}

Visibility and the pub Keyword

By default, everything in Rust is private. The pub keyword makes items accessible outside their defining module:

Developing a Custom Kubernetes Controller in Go

Thu, 20 Jun 2024 06:00:00 +0400

A custom Kubernetes controller manages custom resources within a Kubernetes cluster, allowing for extended functionalities and custom automation.

Step-by-Step Guide

Define Custom Resource:

Define a custom resource definition (CRD) in a YAML file.

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: myresources.mydomain.com
spec:
  group: mydomain.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                size:
                  type: integer
  scope: Namespaced
  names:
    plural: myresources
    singular: myresource
    kind: MyResource
    shortNames:
    - mr

Generate Clientset:

Use kubebuilder to generate clientset, informers, and listers for your CRD.

Rust for IoT Development in 2024: Frameworks, Tools, and Best Practices

Tue, 18 Jun 2024 08:00:00 +0400

The Internet of Things (IoT) continues to transform our world, connecting billions of devices that collect, process, and exchange data. As IoT deployments grow in scale and complexity, the need for reliable, secure, and efficient software becomes increasingly critical. Rust, with its unique combination of memory safety without garbage collection, predictable performance, and modern language features, has emerged as an excellent choice for IoT development.

In this comprehensive guide, we’ll explore Rust’s ecosystem for IoT development as it stands in mid-2024. We’ll examine the frameworks, libraries, and tools that have matured over the years, providing developers with robust building blocks for creating secure and efficient IoT applications. Whether you’re building smart home devices, industrial sensors, wearables, or large-scale IoT platforms, this guide will help you navigate the rich landscape of Rust’s IoT development ecosystem.

Creating a Monitoring Agent in Go

Tue, 18 Jun 2024 06:00:00 +0400

Building a monitoring agent involves collecting metrics from a system and sending them to a monitoring server or displaying them on a dashboard.

Step-by-Step Guide

Define Metrics Structure:

Create a structure to store metrics.

type Metric struct {
    Name  string
    Value float64
}

Collect Metrics:

Implement functions to collect various system metrics (CPU usage, memory usage, etc.).

import (
    "github.com/shirou/gopsutil/cpu"
    "github.com/shirou/gopsutil/mem"
)

func collectCPUMetrics() Metric {
    usage, _ := cpu.Percent(0, false)
    return Metric{Name: "cpu_usage", Value: usage[0]}
}

func collectMemoryMetrics() Metric {
    v, _ := mem.VirtualMemory()
    return Metric{Name: "memory_usage", Value: v.UsedPercent}
}

Send Metrics:

Implement a function to send metrics to a monitoring server (e.g., Prometheus, InfluxDB).

Building a CI/CD Pipeline Tool in Go

Sat, 15 Jun 2024 06:00:00 +0400

Developing a custom CI/CD pipeline tool in Go can help automate the processes of building, testing, and deploying applications. This project involves setting up pipelines, triggering builds, running tests, and deploying applications.

Step-by-Step Guide

Define the Pipeline Structure:

Create a structure to define pipeline stages, jobs, and steps.

type Step struct {
    Name string
    Command string
}

type Job struct {
    Name string
    Steps []Step
}

type Pipeline struct {
    Name string
    Jobs []Job
}

Parse Configuration:

Write a function to parse a pipeline configuration file (e.g., YAML or JSON).

Cloud Networking Best Practices: Designing Secure and Scalable Architectures

Mon, 10 Jun 2024 08:00:00 +0400

Networking is the foundation of cloud infrastructure, connecting your applications, services, and data across regions and to the internet. As organizations migrate more workloads to the cloud, designing secure, scalable, and high-performance network architectures becomes increasingly critical. Poor network design can lead to security vulnerabilities, performance bottlenecks, and operational challenges that impact your entire cloud environment.

This comprehensive guide explores cloud networking best practices across major cloud providers, covering VPC design, security controls, connectivity options, performance optimization, and monitoring strategies. Whether you’re building a new cloud environment or optimizing an existing one, these practices will help you create a robust networking foundation for your cloud infrastructure.

Rust Error Handling: Robust Program Design

Sun, 02 Jun 2024 00:00:00 +0000

Master Rust’s error handling with Result types.

Beyond the Basics: Result and Option

Let’s start with a quick refresher on Rust’s basic error handling types:

Result and Option Recap

// Result: for operations that can fail
fn divide(a: i32, b: i32) -> Result<i32, &'static str> {
    if b == 0 {
        Err("Division by zero")
    } else {
        Ok(a / b)
    }
}

// Option: for values that might be absent
fn find_user(id: u64) -> Option<User> {
    if id == 0 {
        None
    } else {
        Some(User { id, name: "User".to_string() })
    }
}

// Using Result and Option together
fn get_user_name(id: u64) -> Result<String, &'static str> {
    find_user(id).map(|user| user.name).ok_or("User not found")
}

The ? Operator

fn process_data() -> Result<String, &'static str> {
    let data = read_file("data.txt")?;  // Returns early if Err
    let processed = process_string(&data)?;  // Returns early if Err
    Ok(processed)
}

// Works with Option too
fn first_even_number(numbers: &[i32]) -> Option<i32> {
    let first = numbers.first()?;  // Returns None if empty
    if first % 2 == 0 {
        Some(*first)
    } else {
        None
    }
}

Combining Result and Option

fn process_optional_data(data: Option<&str>) -> Result<String, &'static str> {
    // Convert Option to Result
    let data = data.ok_or("No data provided")?;
    
    // Process the data
    if data.is_empty() {
        return Err("Data is empty");
    }
    
    Ok(data.to_uppercase())
}

// Using map and map_err for transformations
fn transform_data(input: Option<&str>) -> Result<i32, String> {
    input
        .ok_or("No input provided".to_string())
        .map(|s| s.parse::<i32>())
        .map_err(|e| format!("Invalid input: {}", e))?
        .map_err(|e| format!("Parse error: {}", e))
}

Custom Error Types

For real-world applications, custom error types provide better organization and flexibility:

Everything you need to know to Master API Creation

Fri, 31 May 2024 06:00:00 +0400

Introduction to APIs

An API (Application Programming Interface) is a set of rules and protocols that allows different software applications to communicate with each other. APIs can be categorized into various types, including REST, SOAP, GraphQL, and RPC. Among these, REST (Representational State Transfer) is the most widely used due to its simplicity and scalability.

This guide focuses primarily on RESTful APIs, which adhere to a set of constraints that make them efficient and easy to use. We’ll also touch on advanced topics like authentication, error handling, and rate limiting.

Progressive Web Apps: Modern Web Development

Mon, 27 May 2024 00:00:00 +0000

Build progressive web applications with service workers.

Understanding Progressive Web Apps

Core Concepts and Principles

Fundamental elements that define Progressive Web Apps:

Progressive Enhancement:

Works for all users regardless of browser choice
Core functionality available to everyone
Enhanced experience for modern browsers
Feature detection over browser detection
Graceful degradation for older browsers

Responsive Design:

Adapts to different screen sizes and orientations
Fluid layouts and flexible images
Mobile-first approach
Touch-friendly interfaces
Consistent experience across devices

App-like Experience:

Zero Trust Architecture: Security Framework Implementation

Mon, 20 May 2024 00:00:00 +0000

Design and implement zero trust security architectures with identity-based access control.

Understanding Zero Trust Security

Zero Trust is a security framework that requires all users and services, whether inside or outside the organization’s network, to be authenticated, authorized, and continuously validated before being granted access to applications and data.

Core Principles of Zero Trust

Verify explicitly: Always authenticate and authorize based on all available data points
Use least privilege access: Limit user access with Just-In-Time and Just-Enough-Access
Assume breach: Minimize blast radius and segment access, verify end-to-end encryption, and use analytics to improve security posture

Traditional vs. Zero Trust Security

Traditional security models operate on the concept of “trust but verify,” where entities inside the network perimeter are inherently trusted. Zero Trust, by contrast, operates on “never trust, always verify,” treating every request as if it originates from an untrusted network.

WebAssembly in the Enterprise: Beyond the Browser

Sat, 18 May 2024 08:00:00 +0400

WebAssembly (Wasm) has evolved far beyond its origins as a browser technology. Initially designed to enable high-performance code execution in web browsers, Wasm has expanded into server-side applications, edge computing, containerization alternatives, and more. Its unique combination of near-native performance, sandboxed security, language-agnostic design, and compact binary format makes it increasingly attractive for enterprise applications seeking portability, security, and efficiency.

This comprehensive guide explores WebAssembly’s role in enterprise applications, covering server-side Wasm, edge computing use cases, containerization alternatives, multi-language development, and security considerations. Whether you’re evaluating Wasm for your organization or looking to expand your existing implementation, these insights will help you leverage WebAssembly’s capabilities to build portable, secure, and high-performance applications across diverse computing environments.

Building CI/CD Pipelines with GitHub Actions: A Comprehensive Guide

Wed, 15 May 2024 06:00:00 +0400

Continuous Integration and Continuous Deployment (CI/CD) have revolutionized how software teams deliver value. By automating the build, test, and deployment processes, CI/CD enables faster, more reliable software delivery with fewer manual interventions. Among the various CI/CD tools available today, GitHub Actions has emerged as a powerful and flexible solution, particularly for teams already using GitHub for source control.

This comprehensive guide will walk you through building effective CI/CD pipelines with GitHub Actions, from basic concepts to advanced implementation strategies, helping you accelerate your software delivery while maintaining quality and security.

How to AWS Assume Role and then revert to the previous role after

Wed, 01 May 2024 06:00:00 +0400

If you need to assume a role in AWS and then revert back to the previous role once complete, you can use the following snippet of code:

# Save original environment variables
ORIGINAL_AWS_ACCESS_KEY_ID="$AWS_ACCESS_KEY_ID"
ORIGINAL_AWS_SECRET_ACCESS_KEY="$AWS_SECRET_ACCESS_KEY"
ORIGINAL_AWS_SESSION_TOKEN="$AWS_SESSION_TOKEN"

# Assume the role and store the output in a variable
assume_role_output=$(aws sts assume-role --role-arn arn:aws:iam::12345678912:role/YourCrossAccountAccessRole --role-session-name "AssumeRoleSession")

# Extract temporary credentials from the assume role output using jq (JSON processor)
export AWS_ACCESS_KEY_ID=$(echo "$assume_role_output" | jq -r '.Credentials.AccessKeyId')
export AWS_SECRET_ACCESS_KEY=$(echo "$assume_role_output" | jq -r '.Credentials.SecretAccessKey')
export AWS_SESSION_TOKEN=$(echo "$assume_role_output" | jq -r '.Credentials.SessionToken')

# Later, if you want to revert back to the original environment variables
# Restore the original environment variables
export AWS_ACCESS_KEY_ID="$ORIGINAL_AWS_ACCESS_KEY_ID"
export AWS_SECRET_ACCESS_KEY="$ORIGINAL_AWS_SECRET_ACCESS_KEY"
export AWS_SESSION_TOKEN="$ORIGINAL_AWS_SESSION_TOKEN"

Understanding the Process

Assuming a role in AWS allows you to temporarily access AWS resources that you wouldn’t have permission to access with your current credentials. After completing your tasks, it’s essential to revert back to your original role for security and access control reasons. This snippet demonstrates how to accomplish that using Bash scripting and the AWS CLI.

Zero Trust in the Cloud: Implementation Guide

Wed, 24 Apr 2024 00:00:00 +0000

Implement zero trust security models in cloud environments with identity management.

Understanding Zero Trust: Core Principles

Before diving into implementation details, let’s establish a clear understanding of Zero Trust principles and how they apply to cloud environments.

What is Zero Trust?

Zero Trust is a security model that assumes no user or system should be inherently trusted, whether inside or outside the traditional network perimeter. Instead, verification is required from everyone trying to access resources in the network.

Infrastructure as Code with Terraform: From Basics to Best Practices

Fri, 12 Apr 2024 06:00:00 +0400

In today’s cloud-centric world, managing infrastructure manually is no longer feasible. As organizations scale their cloud presence, the complexity of managing resources across multiple providers and environments becomes overwhelming. Infrastructure as Code (IaC) has emerged as the solution to this challenge, with Terraform standing out as one of the most powerful and flexible IaC tools available.

This comprehensive guide will take you through the journey of mastering Terraform—from understanding core concepts to implementing advanced techniques and best practices that enable you to manage infrastructure at scale with confidence and efficiency.

Cloud-Native Security: Modern Protection Strategies

Fri, 12 Apr 2024 00:00:00 +0000

Implement comprehensive security for cloud-native applications including container security.

Cloud-Native Security Fundamentals

The Cloud-Native Security Landscape

Understanding the unique security challenges:

Cloud-Native Architecture Characteristics:

Distributed and decentralized
Ephemeral and immutable
API-driven and programmable
Highly automated
Dynamically orchestrated
Microservices-based
Infrastructure as code

Security Implications:

Expanded attack surface
Dynamic trust boundaries
Short-lived resources
Increased complexity
Shared responsibility model
Infrastructure as code vulnerabilities
Supply chain risks

The 4C’s of Cloud-Native Security:

┌───────────────────────────────────────────────────────────┐
│                                                           │
│                        Cloud                             │
│                                                           │
│  ┌───────────────────────────────────────────────────┐    │
│  │                                                   │    │
│  │                    Cluster                        │    │
│  │                                                   │    │
│  │  ┌───────────────────────────────────────────┐    │    │
│  │  │                                           │    │    │
│  │  │               Container                   │    │    │
│  │  │                                           │    │    │
│  │  │  ┌───────────────────────────────────┐    │    │    │
│  │  │  │                                   │    │    │    │
│  │  │  │             Code                  │    │    │    │
│  │  │  │                                   │    │    │    │
│  │  │  └───────────────────────────────────┘    │    │    │
│  │  │                                           │    │    │
│  │  └───────────────────────────────────────────┘    │    │
│  │                                                   │    │
│  └───────────────────────────────────────────────────┘    │
│                                                           │
└───────────────────────────────────────────────────────────┘

Cloud-Native Security Principles:

Python Web Development: Building Modern Applications

Fri, 12 Apr 2024 00:00:00 +0000

Build modern web applications using Python frameworks like Flask and Django with database integration.

Setting Up Your Python Web Development Environment

When I first started building web applications with Python, I made the classic mistake of jumping straight into Django without understanding the fundamentals. Three weeks later, I was drowning in middleware, models, and migrations without grasping why any of it mattered. That’s why we’re starting this guide with the foundation—understanding what Python web development actually means and setting up an environment that’ll serve you well throughout your journey.

Essential Policies for Administering an AWS EKS Cluster

Fri, 22 Mar 2024 06:00:00 +0400

So, what policies does my role need to create an AWS EKS cluster and be the admin?

AmazonEKSClusterPolicy: This policy grants permissions to create and manage EKS clusters. It includes actions like eks:CreateCluster, eks:DescribeCluster, eks:UpdateClusterConfig, eks:DeleteCluster, etc.
AmazonEKSServicePolicy: This policy allows the necessary permissions for the EKS service to manage resources on your behalf. It includes actions like eks:DescribeUpdates, eks:ListClusters, eks:ListUpdates, etc.
AmazonEKSServiceRolePolicy: This policy is attached to the IAM role assumed by the EKS service. It allows the service to perform necessary operations within your AWS account. This policy is typically managed by AWS and attached to the service role.

Show the Top 10 Largest Directories on Linux

Wed, 13 Mar 2024 06:00:00 +0400

If you need to see the top 10 largest directories on your Linux system, you can use the following command:

du -h --max-depth=1 / | sort -rh | head -n 11

Alternative

If you are okay to install additional software, then you can use a tool like ncdu to do the same, but with a lot more options and more features.

Installing `ncdu`

ncdu is a software package that standards for “NCurses Disk Usage” and is a disk utility tool for Unix based systems.

Cloud Cost Optimization Strategies: Maximizing ROI in the Cloud

Fri, 01 Mar 2024 06:00:00 +0400

As organizations continue to migrate workloads to the cloud, many are experiencing the phenomenon known as “cloud shock”—the realization that cloud costs are significantly higher than anticipated. While the cloud offers tremendous benefits in terms of agility, scalability, and innovation, these advantages can come at a substantial cost if not managed properly. According to Gartner, through 2024, nearly 60% of organizations will encounter public cloud cost overruns that negatively impact their budgets.

Retrieve the Latest Versioned Tag from AWS ECR in Bash

Wed, 21 Feb 2024 06:00:00 +0400

Managing Docker images in Amazon Elastic Container Registry (ECR) is a common task for many developers and DevOps practitioners. Often, you need to retrieve the latest versioned tag from a repository to streamline deployment processes or ensure compatibility with the most recent features or fixes.

In this post, we’ll explore a simple Bash command using the AWS CLI and jq to fetch the latest versioned tag from an ECR repository.

Designing Scalable Systems in AWS: Architecture Patterns for Growth

Mon, 05 Feb 2024 06:00:00 +0400

In today’s digital landscape, building systems that can scale effectively is no longer a luxury—it’s a necessity. Whether you’re launching a startup that might experience overnight success or managing enterprise applications with predictable but substantial growth, your architecture must be designed to scale seamlessly. Amazon Web Services (AWS) provides a rich ecosystem of services and tools to build highly scalable systems, but knowing how to leverage these resources effectively requires understanding key architectural patterns and best practices.

How to install MySQL on AmazonLinux2023

Mon, 29 Jan 2024 06:00:00 +0400

If you are using Amazon Linux 2023 base-image, and you have tried to run yum install -y mysql, you will soon realize that it doesn’t work.

Instead install MySQL on Amazon Linux 2023 like this:

sudo dnf update -y
sudo dnf install mariadb105-server

For advanced use-cases where you are installing this in a Docker-in-Docker environment, do it without the sudo, as follows:

dnf update -y
dnf install mariadb105-server

Now if you run mysql, you will no longer get the mysql: command not found message.

Object-Oriented Programming in Python

Mon, 29 Jan 2024 00:00:00 +0000

Master OOP concepts in Python including classes.

Introduction and Setup

When I first started programming in Python, I thought object-oriented programming was just a fancy way to organize code. I couldn’t have been more wrong. After years of building everything from web applications to data processing pipelines, I’ve learned that OOP isn’t just about organization—it’s about modeling real-world problems in ways that make your code more maintainable, reusable, and intuitive.

Python Testing and Debugging: Quality Assurance

Thu, 18 Jan 2024 00:00:00 +0000

Master testing frameworks.

Understanding the Testing Mindset and Environment Setup

I’ve seen countless developers jump straight into writing tests without understanding why they’re doing it. They treat testing like a checkbox exercise—something to appease their team lead or satisfy code coverage metrics. But here’s what I’ve learned after years of debugging production failures at 3 AM: testing isn’t about proving your code works; it’s about discovering how it fails.

The mindset shift from “my code is perfect” to “my code will break in ways I haven’t imagined” is fundamental. When you write tests, you’re not just verifying functionality—you’re documenting your assumptions, creating safety nets for future changes, and building confidence in your system’s behavior under stress.

Choosing the Right Cloud Architecture: A Decision Framework for Modern Applications

Mon, 15 Jan 2024 06:00:00 +0400

In today’s rapidly evolving technology landscape, selecting the right cloud architecture is one of the most consequential decisions that organizations face. The architecture you choose not only impacts your application’s performance, scalability, and reliability but also significantly affects your development velocity, operational overhead, and total cost of ownership. With multiple architectural patterns available—from traditional monoliths to microservices, serverless, and various hybrid approaches—making an informed decision requires a structured approach that considers your specific business context, technical requirements, and organizational constraints.

Python Data Science: Analytics and Machine Learning

Sat, 13 Jan 2024 00:00:00 +0000

Master Python for data science with NumPy.

Setting Up Your Data Science Environment and Understanding the Ecosystem

Environment setup might seem boring, but I’ve learned it’s where most data science projects succeed or fail. You can have the best analysis in the world, but if your colleagues can’t reproduce it because of dependency conflicts, your work becomes worthless. Getting this foundation right from the start saves enormous headaches later.

The Python data science ecosystem has evolved dramatically over the past decade. What started as a collection of separate tools has become an integrated platform that rivals specialized statistical software. Understanding how these pieces fit together will make you more effective at solving real problems.

Python Data Structures: Algorithms and Implementation

Tue, 09 Jan 2024 00:00:00 +0000

Master Python’s built-in data structures and implement custom algorithms for efficient data manipulation and problem-solving.

Introduction and Fundamentals

Last month, I watched a developer spend three hours debugging why their web application was timing out. The culprit wasn’t a complex algorithm or a database issue - it was using a list to check if user IDs were valid. With 50,000 users, each login attempt was checking potentially all 50,000 entries. A simple change to a set reduced login time from 2 seconds to 2 milliseconds.

Asynchronous Programming in Python: Building High-Performance Applications

Wed, 03 Jan 2024 00:00:00 +0000

Master Python’s asynchronous programming capabilities to build fast, scalable applications that handle thousands of concurrent operations efficiently.

Why Async Programming Matters

Asynchronous programming can seem like magic when you see a single Python process handle 10,000 concurrent connections. How can one thread outperform traditional multi-threaded servers? The answer lies in efficiency and smart resource management.

Think of a restaurant where waiters take one order, go to the kitchen, wait for the food to cook, bring it back, then serve the next customer. If your meal takes 20 minutes, other customers wait 20 minutes just to place their order.

Python Fundamentals: Complete Programming Foundation

Sat, 30 Dec 2023 00:00:00 +0000

Build a solid foundation in Python programming with comprehensive coverage of syntax.

Introduction and Setup

Python has earned its reputation as one of the most approachable programming languages. What takes 20 lines of code in other languages often requires just 3 lines in Python. This simplicity isn’t accidental—it’s the result of deliberate design choices that prioritize readability and developer productivity.

When Guido van Rossum created Python, he built it around a philosophy of clean, readable code. The result is a language that reads almost like English, making it perfect for beginners while remaining powerful enough for complex applications. This guide will take you from Python basics to building real-world applications.

Run any version of Terrform using Docker

Fri, 22 Dec 2023 06:00:00 +0400

So our friend Docker comes around for another usecase.

Run Terraform (any version) from Docker

In this example, we will try and configure Terraform 1.4.0 through Docker, so that we don’t need to install it on our host system.

alias terraform14='docker run --rm -it -w $PWD:$PWD -v $PWD:$PWD hashicorp/terraform:1.4.0'

To use it, we simply run a Terraform command:

terraform14 -version

Next let’s try another Terraform version as well

alias terraform15='docker run --rm -it -w $PWD:$PWD -v $PWD:$PWD hashicorp/terraform:1.5.0'

To use it, like before:

Select * to Show Database Table Sizes MariaDB

Thu, 21 Dec 2023 06:00:00 +0400

In database management, understanding the size of your tables is crucial for optimizing performance and ensuring efficient resource utilization. If you’re a technical enthusiast or a seasoned database administrator working with MariaDB, this blog post is tailored just for you. Today, we’ll unravel the mystery behind MariaDB database table sizes using a powerful SQL query.

SELECT 
  table_schema AS DB_NAME, 
  TABLE_NAME, 
  (DATA_LENGTH+INDEX_LENGTH)/1024/1024/1024 AS TABLE_SIZE_in_MB
FROM 
  information_schema.TABLES
ORDER BY 
  TABLE_SIZE_in_MB DESC

Exploring MariaDB Table Sizes

MariaDB stands out as a robust and reliable option. To gain insights into your database’s table sizes, we’re going to wield the mighty SQL language. Our tool of choice is a concise yet potent query that taps into the depths of MariaDB’s information schema.

Graceful Shutdown Patterns in Go

Sun, 10 Dec 2023 00:00:00 +0000

Implement proper shutdown procedures for Go applications.

Signal Handling Fundamentals

At the core of graceful shutdown is the ability to detect and respond to termination signals. Before diving into complex implementations, let’s establish a solid understanding of signal handling in Go.

Understanding OS Signals

Operating systems communicate with processes through signals. The most common signals relevant to application lifecycle management include:

SIGINT (Ctrl+C): Interrupt signal, typically sent when a user presses Ctrl+C
SIGTERM: Termination signal, the standard way to request graceful termination
SIGKILL: Kill signal, forces immediate termination (cannot be caught or ignored)
SIGHUP: Hangup signal, traditionally used to indicate a controlling terminal has closed

In Go, we can capture and handle these signals using the os/signal package and channels:

Rate Limiting Strategies in Go

Fri, 08 Dec 2023 00:00:00 +0000

Implement sophisticated rate limiting algorithms and patterns in Go for API protection.

Rate Limiting Fundamentals

Rate limiting is a strategy to control the rate at which a user, service, or system can access a resource or perform operations. Before diving into complex implementations, let’s establish a solid understanding of the core concepts and basic approaches.

Core Concepts and Terminology

Rate limiting involves several key concepts:

Request Rate: The number of requests per unit time (e.g., 100 requests per second)
Burst: A temporary spike in request rate
Quota: The maximum number of requests allowed in a given time window
Throttling: The act of delaying or rejecting requests that exceed defined limits
Rate Limiter: The component that enforces rate limits

Simple Counter-Based Rate Limiter

Let’s start with a basic implementation—a fixed window counter rate limiter:

Advanced Go Reflection and Code Generation

Wed, 22 Nov 2023 00:00:00 +0000

Master Go’s reflection capabilities and code generation techniques for building flexible.

#Go is known for simplicity, but sometimes you need more flexibility. Reflection lets you inspect types and values at runtime, while code generation creates Go code automatically. Both techniques help eliminate repetitive code and build more flexible systems.

When You Need These Techniques

Most Go code doesn’t need reflection or code generation. But they’re valuable when:

Building frameworks: ORMs, web frameworks, and serialization libraries
Eliminating boilerplate: Generating repetitive struct methods
Dynamic behavior: Handling unknown types at runtime
API tooling: Generating client libraries from definitions
Testing utilities: Creating mocks and test helpers

Reflection vs Code Generation

Reflection happens at runtime:

The Future Prospects of DevOps in an AI World

Mon, 20 Nov 2023 06:00:00 +0400

Abstract

DevOps has become an integral part of modern software development, emphasizing communication and collaboration between software developers and IT operations professionals. However, with the rise of artificial intelligence (AI), the future role and necessity of devops has been brought into question. This paper explores the prospects for devops in an increasingly AI-driven world, including devops’ potential contributions to and collaboration with AI, as well as the possibility of eventual replacement by intelligent systems. Both theoretical analysis and real-world trajectory suggest devops retaining relevance, albeit with an evolving role and skillset demands.

Go Pipeline Patterns for Data Processing

Thu, 09 Nov 2023 00:00:00 +0000

Build efficient data processing pipelines in Go using channel patterns.

#Processing large amounts of data efficiently is a common challenge. Pipeline patterns break complex processing into stages, where each stage does one thing well and passes results to the next stage.

What Are Pipeline Patterns?

Think of an assembly line: each worker performs a specific task and passes the work to the next person. Pipeline patterns work similarly:

Input Stage: Receives raw data
Processing Stages: Transform, filter, or enrich data
Output Stage: Sends results somewhere useful

Each stage runs concurrently, so while stage 1 processes item N, stage 2 can process item N-1, and stage 3 can process item N-2.

Event Sourcing Implementation in Go

Fri, 03 Nov 2023 00:00:00 +0000

Build event-sourced systems in Go with CQRS patterns.

#Most applications store only current state - when something changes, the old data is lost. Event sourcing takes a different approach: store every change as an immutable event, preserving the complete history.

The Problem with State-Based Storage

Traditional applications work like this:

// Traditional approach - only current state
type Account struct {
    ID      string
    Balance int
    Status  string
}

// When balance changes, old value is lost
func (a *Account) Withdraw(amount int) {
    a.Balance -= amount  // History is gone
}

Problems with this approach:

Supercharge Your Code with Amazon CodeWhisperer

Sun, 29 Oct 2023 06:00:00 +0400

Amazon CodeWhisperer is a cutting-edge service that leverages advanced AI and machine learning to provide real-time code generation, recommendations, and security analysis. As a developer, CodeWhisperer can supercharge your productivity and code quality.

Key Capabilities

Neural Code Generation

CodeWhisperer utilizes powerful neural networks to generate code snippets and entire functions on demand. The advanced models are trained on millions of code samples and can produce idiomatic, human-readable code for a wide variety of programming languages.

A Deep Dive into Machine Learning Algorithms

Sat, 28 Oct 2023 06:00:00 +0400

Machine learning algorithms are the backbone of modern artificial intelligence. They enable computers to learn and make predictions or decisions without being explicitly programmed. In this comprehensive guide, we will delve into common machine learning algorithms, providing detailed explanations and code examples to help you understand their inner workings. Whether you’re a beginner or an experienced data scientist, this post will be a valuable resource to enhance your understanding of machine learning.

What is GitHub? A Comprehensive Guide from Basics to Advanced

Fri, 27 Oct 2023 06:00:00 +0400

GitHub is a platform that has revolutionized the world of software development, enabling individuals and teams to collaborate efficiently on projects of all sizes. In this comprehensive guide, we’ll explore GitHub from the very basics to the most advanced features. Whether you’re a novice or an experienced developer, you’ll find valuable insights and tips to enhance your understanding of GitHub.

Part 1: Git Basics

Before diving into GitHub, it’s essential to grasp the fundamental concepts of Git, the version control system that underlies GitHub.

Connect IPv4 and IPv6 Networks Seamlessly with Amazon VPC Lattice

Thu, 26 Oct 2023 06:00:00 +0400

As the internet continues to grow, the transition from IPv4 to IPv6 has become more critical. Organizations need to manage both IP stacks efficiently and ensure seamless connectivity. Amazon Web Services (AWS) offers a groundbreaking solution: Amazon VPC Lattice. In this advanced guide, we’ll delve deeper into Amazon VPC Lattice, its technical details, and provide code examples for advanced users.

A Lattice of Connectivity

Amazon VPC Lattice simplifies the coexistence of IPv4 and IPv6 stacks within your Virtual Private Cloud (VPC). The innovation lies in its ability to bridge the gap between these two IP versions without the need for Network Address Translation (NAT) devices. Let’s explore the capabilities of VPC Lattice and its significance in modern networking.

Building Event-Driven Architectures with Amazon EventBridge

Wed, 25 Oct 2023 06:00:00 +0400

In the realm of real-time data streaming applications, managing the routing and processing of events efficiently is a complex challenge. Amazon Web Services (AWS) has a powerful solution: Amazon EventBridge. In this advanced guide, we’ll delve deeper into EventBridge, its key concepts, and provide code examples for advanced users.

Splitting Terraform Modules into Separate Git Repositories

Tue, 24 Oct 2023 06:00:00 +0400

In the world of Infrastructure as Code (IaC), Terraform has emerged as a powerful tool for managing infrastructure resources. As your Terraform codebase grows, managing monolithic code can become challenging. In this advanced-level blog post, we will explore the process of moving Terraform modules into separate Git repositories and referencing these modules across multiple repositories. This approach can help you achieve better code organization, reusability, and collaboration in your infrastructure provisioning projects.

Accelerating Machine Learning with SageMaker Jumpstart

Sun, 22 Oct 2023 06:00:00 +0400

Machine learning (ML) projects can be complex, time-consuming, and resource-intensive. Amazon SageMaker Jumpstart aims to change that by providing pre-built solutions, pre-trained models, and end-to-end ML capabilities. In this advanced guide, we’ll dive deep into SageMaker Jumpstart and provide code examples to illustrate its power.

Unleashing ML Potential

Amazon SageMaker Jumpstart is designed to accelerate your ML journey. It offers a wide range of pre-built solutions and pre-trained models for various ML use cases, including natural language processing, computer vision, and more. Let’s delve into the capabilities of SageMaker Jumpstart and how it can make your ML projects more efficient.

Understanding the AWS Well-Architected Framework

Thu, 19 Oct 2023 06:00:00 +0400

The AWS Well-Architected Framework is more than just a set of best practices; it’s a blueprint for success in the cloud. It offers a comprehensive guide to building high-quality, efficient, and cost-effective architectures on Amazon Web Services (AWS). In this blog post, we’ll delve into the key principles and pillars of the AWS Well-Architected Framework and explore how you can leverage it to ensure your cloud infrastructure is robust and resilient.

Mastering Advanced Networking in EKS and Kubernetes

Mon, 16 Oct 2023 06:00:00 +0400

Kubernetes has revolutionized container orchestration, and Amazon’s Elastic Kubernetes Service (EKS) is one of the most popular managed Kubernetes solutions available today. While getting started with EKS and Kubernetes is relatively straightforward, mastering advanced networking topics is essential for managing complex workloads and achieving optimal performance. In this comprehensive guide, we will explore advanced networking concepts in EKS and Kubernetes, accompanied by code examples and practical insights.

1. VPC Design and EKS Setup

When working with EKS, it’s crucial to have a well-architected VPC. This section will cover best practices for VPC design, creating EKS clusters, and securing them with security groups and Network ACLs. Let’s look at a snippet of Terraform code to create a VPC:

How to Ignore SSL Certificates Globally in Git

Sat, 14 Oct 2023 06:00:00 +0400

In the world of software development, Git is an indispensable tool for version control. However, when working with repositories that use SSL certificates, you might encounter situations where you need to ignore SSL certificate verification globally. Whether it’s for testing or debugging purposes, this guide will show you how to ignore SSL certificates globally in Git and even disable SSL certificate checks altogether. We’ll cover everything from the basics to advanced configurations to help you manage SSL certificates effectively in your Git workflow.

Semantic Versioning with npm

Fri, 13 Oct 2023 06:00:00 +0400

Semantic Versioning, often referred to as SemVer, is a crucial convention within the Node.js ecosystem. It provides a clear and structured way of versioning software, ensuring that developers can easily understand the impact of version changes. In this blog post, we’ll explore the principles of Semantic Versioning and how npm (Node Package Manager) leverages it to manage packages effectively.

Understanding Semantic Versioning

Semantic Versioning is based on a three-digit version number, often expressed as x.y.z, where each digit has a specific meaning:

Understanding Peer Dependencies in Node Modules

Thu, 12 Oct 2023 06:00:00 +0400

When working with Node.js and managing packages for your projects, you’re likely familiar with the dependencies and devDependencies sections in a package.json file. These sections define the packages your project depends on for both production and development purposes. However, there’s another crucial field often overlooked but equally important: peerDependencies.

In this blog post, we will delve into the concept of peerDependencies and how they differ from regular dependencies and devDependencies.

How to Programmatically get Amazon IP Ranges/CIDRs

Wed, 11 Oct 2023 06:00:00 +0400

Amazon Web Services (AWS) operates an extensive network infrastructure with a vast number of IP addresses and CIDR blocks. As a developer or network administrator, you may need to programmatically retrieve the IP ranges or CIDRs associated with AWS regions and services for various reasons, such as configuring firewall rules or network security groups. In this guide, we’ll show you how to accomplish this using Python.

Prerequisites

Before we dive into the code, make sure you have the following prerequisites in place:

The Ultimate Guide to Emacs: Mastering the Art of CLI Programming

Tue, 10 Oct 2023 06:00:00 +0400

In the realm of command-line interface (CLI) programming, Emacs stands as a legendary text editor, known for its immense power and unparalleled extensibility. For decades, Emacs has been the tool of choice for seasoned CLI programmers who demand efficiency and customization. In this ultimate guide, we will explore advanced and expert ways to harness the full potential of Emacs, helping you become an amazing CLI programmer.

Introduction to Emacs

What is Emacs?

Emacs is a highly extensible, open-source text editor with a rich history dating back to the 1970s. It’s renowned for its “everything is a buffer” philosophy, which means you can edit not only code but also emails, calendar events, and more from within Emacs.

The Ultimate Guide to VI: Mastering the Art of CLI Programming

Mon, 09 Oct 2023 06:00:00 +0400

In the world of command-line interface (CLI) programming, efficiency is paramount. And when it comes to text editing in the CLI, there’s no tool more legendary than VI. This powerful, yet enigmatic text editor has been the choice of seasoned CLI programmers for decades. In this ultimate guide, we will explore advanced and expert ways to harness the full potential of VI, helping you become an amazing CLI programmer.

Introduction to VI

What is VI?

VI, which stands for “Visual Editor,” is a highly efficient and lightweight text editor that comes pre-installed on most Unix-like systems. Its minimalist design and keyboard-centric interface make it a favorite among power users who spend a lot of time in the terminal.

AWS Assume to another role

Sun, 08 Oct 2023 06:00:00 +0400

OUT=$(aws sts assume-role --role-arn arn:aws:iam::0123456789:role/OrganizationAccountAccessRole --role-session-name test)
export AWS_ACCESS_KEY_ID=$(echo $OUT | cut -d '"' -f 6 )
export AWS_SECRET_ACCESS_KEY=$(echo $OUT | cut -d '"' -f 10 )
export AWS_SESSION_TOKEN=$(echo $OUT | cut -d '"' -f 14 )
aws sts get-caller-identity

Service Discovery Patterns in Go

Wed, 04 Oct 2023 00:00:00 +0000

Implement service discovery mechanisms in Go microservices using various patterns and tools for dynamic service registration and lookup.

Service Discovery Fundamentals

Before diving into implementation details, let’s establish a solid understanding of service discovery concepts and their role in distributed systems.

The Service Discovery Problem

In a traditional monolithic application, components communicate through in-memory function calls or well-known local interfaces. In distributed systems, however, services run on different machines with their own network locations, creating several challenges:

Programming Languages Series

Mon, 02 Oct 2023 06:00:00 +0400

1. Introduction

Welcome to our Programming Languages Series! In this series, we’ll explore various programming languages, understand their purposes, provide code examples, and discuss when to use each one. Let’s begin with an introduction to programming languages.

What Are Programming Languages?

Programming languages are a means of communication between humans and computers. They allow developers to instruct computers to perform specific tasks, ranging from simple calculations to complex data processing and application development.

Go Worker Pool Patterns: Scalable Concurrent Processing

Thu, 28 Sep 2023 00:00:00 +0000

Master worker pool patterns in Go for building scalable.

#Processing many tasks concurrently is a common need, but creating unlimited goroutines can overwhelm your system. Worker pools solve this by using a fixed number of workers to process tasks from a queue.

The Problem with Unlimited Goroutines

Consider processing 10,000 images:

// Don't do this - creates 10,000 goroutines
for _, image := range images {
    go processImage(image)
}

This approach can:

Exhaust memory with too many goroutines
Overwhelm the CPU with context switching
Crash your system under high load
Make it hard to control resource usage

Worker Pool Solution

Instead, use a fixed number of workers:

Docker Deep Dive Series

Fri, 22 Sep 2023 06:00:00 +0400

1. Getting Started

In this first part of the series, we will kick things off by getting Docker installed and running on your system. Docker makes it easy to package and distribute applications as containers, ensuring consistent environments across different stages of the development and deployment pipeline.

Let’s jump right in and get Docker up and running!

Prerequisites

Before we start, ensure that you have the following prerequisites installed on your system:

Go Atomic Operations: Lock-Free Programming

Thu, 21 Sep 2023 00:00:00 +0000

Master Go’s atomic operations for building high-performance.

Understanding Go’s Memory Model

Before diving into atomic operations, it’s essential to understand Go’s memory model, which defines the rules for how memory operations in one goroutine become visible to another. This understanding forms the foundation for correct concurrent programming in Go.

Memory Ordering and Visibility

Go’s memory model is based on the happens-before relationship, which determines when the effects of one goroutine’s memory operations become visible to another goroutine:

Machine Learning Mastery Series

Wed, 13 Sep 2023 06:00:00 +0400

Part 1. Introduction to Machine Learning

Welcome to the Machine Learning Mastery Series, a comprehensive journey into the exciting world of machine learning. In this first installment, we’ll lay the foundation by exploring the fundamentals of machine learning, its types, and the essential concepts that underpin this transformative field.

What is Machine Learning?

Machine learning is a subfield of artificial intelligence (AI) that focuses on developing algorithms and models that enable computers to learn from and make predictions or decisions based on data. Unlike traditional programming, where explicit instructions are provided to solve a specific task, machine learning systems learn patterns and relationships from data to make informed decisions.

Kubernetes Mastery

Sun, 03 Sep 2023 06:00:00 +0400

Part 1. Introduction

Welcome to the Kubernetes Mastery Series! In this first part, we’ll set up a Kubernetes cluster using KinD (Kubernetes in Docker). This series will build on concepts covered in our Ultimate Guide to Kubernetes Deployment Strategies and provide practical implementations of DevOps security best practices.

Prerequisites:

Docker
kubectl
KinD

# Step 1: Install Docker
# Step 2: Install kubectl
# Step 3: Install KinD

# Step 4: Create a KinD cluster
kind create cluster --name my-cluster --config - <<EOF
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
- role: worker
- role: worker
EOF

# Step 5: Set kubectl context
kubectl cluster-info --context kind-my-cluster

# Step 6: Verify cluster nodes
kubectl get nodes

Part 2. Deploying Your First App

In this second part, we’ll explore how to deploy your first application to the Kubernetes cluster you set up in Part 1.

Advanced Go Concurrency Patterns

Sun, 03 Sep 2023 00:00:00 +0000

Master sophisticated concurrency patterns in Go including worker pools.

#Go’s concurrency model is powerful, but building distributed systems requires more than basic goroutines and channels. You need patterns that handle coordination across services, manage failures gracefully, and scale under load.

Beyond Basic Concurrency

Most Go tutorials cover the basics: launching goroutines, sending values through channels, and using select statements. But real distributed systems face challenges like:

Service coordination: Multiple services need to work together
Failure handling: Networks partition, services crash, timeouts occur
Load management: Systems must handle varying traffic patterns
Resource coordination: Shared resources need careful management

Patterns You’ll Learn

This guide covers advanced concurrency patterns for distributed systems:

Managing Multiple Environments with Terraform Workspaces

Sat, 02 Sep 2023 06:00:00 +0400

Managing infrastructure across multiple environments such as development, staging, and production can be a daunting task. Terraform, a popular Infrastructure as Code (IaC) tool, offers a powerful feature known as workspaces that can help you efficiently manage and maintain separate environments within a single configuration. In this technical blog post, we’ll explore Terraform workspaces, how they work, and best practices for utilizing them effectively.

Understanding Terraform Workspaces

Terraform workspaces provide a way to manage distinct instances of the same infrastructure configuration. Each workspace maintains its state files and variables, allowing you to create isolated environments for different purposes. This isolation prevents potential conflicts and allows you to make changes to one environment without affecting others.

Controlling and Understanding Parallelism Impact on the DAG

Fri, 01 Sep 2023 06:00:00 +0400

When working with large-scale infrastructure deployments, managing the provisioning and orchestration of resources efficiently becomes crucial. Terraform, a widely-used Infrastructure as Code (IaC) tool, offers a feature known as parallelism to accelerate the deployment process. In this blog post, we’ll delve into parallelism in Terraform, how it affects the Directed Acyclic Graph (DAG), and how you can control and optimize its usage.

Understanding Parallelism and the DAG

Parallelism refers to the ability to execute multiple tasks simultaneously. In the context of Terraform, parallelism enables the provisioning of resources in parallel, speeding up the infrastructure deployment process. However, parallelism introduces complexities due to resource dependencies and potential conflicts.

How to add Payment Subscriptions with Stripe in Django

Thu, 31 Aug 2023 06:00:00 +0400

Integrating Stripe subscriptions into your Django site involves several steps. Here’s a high-level overview of the process. Please note that the exact implementation can vary based on your specific requirements.

Steps involved

If you haven’t already, sign up for a Stripe account at https://stripe.com. Once you’ve signed up, you’ll need your API keys: a Publishable Key (for the client-side) and a Secret Key (for server-side interactions).

Private Application Load Balancer for EKS in Terraform

Wed, 30 Aug 2023 06:00:00 +0400

Amazon Web Services (AWS) provides a powerful combination of services for building, deploying, and managing applications. Amazon Elastic Kubernetes Service (EKS) is a managed Kubernetes service that simplifies the process of deploying, managing, and scaling containerized applications using Kubernetes. In certain scenarios, you might want to deploy a private Application Load Balancer (ALB) in front of your private EKS cluster to handle incoming traffic efficiently. In this guide, we’ll walk through the process of setting up a private ALB for your private EKS cluster using Terraform, along with best practices and intricate details.

Kubernetes vs Docker Swarm for Container Orchestration

Tue, 29 Aug 2023 06:00:00 +0400

Container orchestration has become a cornerstone of modern application deployment and management. Two prominent contenders in the realm of container orchestration are Kubernetes and Docker Swarm. Both offer powerful solutions for automating the deployment, scaling, and management of containerized applications. In this in-depth comparison, we’ll delve into the strengths, features, and nuances of Kubernetes and Docker Swarm to help you make an informed choice for your container orchestration needs.

Understanding Kubernetes

Kubernetes, often referred to as K8s, has emerged as a de facto standard for container orchestration. It provides an extensive set of features for managing containerized applications, ensuring high availability, scalability, and seamless deployments. Kubernetes excels in orchestrating complex microservices architectures and applications with intricate scaling requirements.

Setting Comprehensive CI/CD Pipeline with Jenkins and Docker

Mon, 28 Aug 2023 06:00:00 +0400

In today’s dynamic software landscape, the fusion of Continuous Integration and Continuous Deployment (CI/CD) pipelines with robust tools like Jenkins and Docker has emerged as a cornerstone of efficient and reliable application delivery. This detailed tutorial will provide you with an in-depth walkthrough, guiding you step by step through the intricate process of configuring a comprehensive CI/CD pipeline using Jenkins and Docker. By the end of this tutorial, you’ll be equipped to seamlessly incorporate DevOps practices, elevating your software delivery process to new heights.

Navigating Microsoft Azure for Seasoned AWS Experts

Sun, 27 Aug 2023 06:00:00 +0400

In the ever-evolving landscape of cloud computing, two mammoth players, Amazon Web Services (AWS) and Microsoft Azure, have emerged as titans, offering an extensive array of services that cater to a diverse spectrum of business needs. If you’ve already amassed a wealth of knowledge and experience in AWS and are now yearning to broaden your cloud horizons, this comprehensive guide is designed to be your compass. Together, we’ll embark on a journey to seamlessly transition your AWS proficiency into the realm of Microsoft Azure, unraveling parallels between their services and enriching your cloud expertise.

Advanced Go Memory Management

Sun, 27 Aug 2023 00:00:00 +0000

Master Go’s memory model.

Understanding Go’s Memory Model

Before diving into optimization techniques, it’s essential to understand how Go manages memory at a fundamental level. Go’s memory model defines not just how memory is allocated and freed, but also the guarantees around memory access in concurrent programs.

Stack vs. Heap Allocation

Go uses a hybrid approach to memory allocation, utilizing both stack and heap:

package main

import (
	"fmt"
	"runtime"
)

func main() {
	// Stack allocation - x doesn't escape to the heap
	x := 42
	
	// Heap allocation - y escapes to the heap
	y := &x
	
	// Force GC to demonstrate the concept
	runtime.GC()
	
	// Print memory statistics
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	
	fmt.Printf("Stack variable: %d\n", x)
	fmt.Printf("Heap reference: %d\n", *y)
	fmt.Printf("Heap allocations: %d bytes\n", m.HeapAlloc)
}

The Go compiler uses escape analysis to determine whether a variable should be allocated on the stack or heap. Variables allocated on the stack are automatically freed when the function returns, while heap allocations are managed by the garbage collector.

Navigating Google Cloud Platform (GCP) for AWS Experts

Sat, 26 Aug 2023 06:00:00 +0400

In today’s rapidly evolving landscape of cloud computing, Amazon Web Services (AWS) and Google Cloud Platform (GCP) have emerged as prominent contenders, furnishing an extensive array of services tailored to cater to the dynamic requirements of modern businesses. If you’re already versed in the intricacies of AWS and are now seeking to broaden your cloud horizons, this comprehensive guide is poised to be your beacon. We’ll embark on a journey of bridging the gap between your existing AWS proficiency and your newfound GCP expertise, ensuring your transition is not just smooth, but also illuminating.

Create a slug from a name in MySQL/MariaDB

Fri, 25 Aug 2023 06:00:00 +0400

How to create a slug from the name of an item in MySQL/MariaDB.

UPDATE my_table
SET slug = LOWER(REGEXP_REPLACE(REPLACE(REPLACE(REPLACE(name, ' ', '-'), 'and', '-'), '[^a-zA-Z0-9-]', ''), '-+', '-'));

Secure Efficient Server Management with AWS Systems Manager

Thu, 24 Aug 2023 06:00:00 +0400

In the ever-evolving landscape of cloud computing, AWS (Amazon Web Services) continually introduces innovative solutions to enhance operational efficiency, security, and ease of management. One such powerful tool is AWS Systems Manager (SSM), which empowers users to manage their server infrastructure without the need for SSH access and traditional EC2 key pairs. In this comprehensive guide, we’ll delve into setting up AWS SSM, exploring its advanced use cases, and demonstrating how it can transform your workflow.

How to Get a List of Available Regions from AWS CLI

Wed, 23 Aug 2023 06:00:00 +0400

AWS (Amazon Web Services) is a prominent cloud service provider that offers a wide range of services to businesses and individuals worldwide. One of the fundamental concepts in AWS is regions, which are distinct geographical locations hosting AWS infrastructure. Understanding regions is crucial for optimizing your cloud infrastructure’s performance, data residency, and compliance requirements. In this blog post, we’ll dive into the world of AWS regions, learn how to list available regions using the AWS CLI, and explore a handy command to fetch region details in a more reader-friendly format.

[Solved] A Number After a Double Reversal in Python

Tue, 22 Aug 2023 06:00:00 +0400

The problem

Reversing an integer means to reverse all its digits.

For example, reversing 2021 gives 1202. Reversing 12300 gives 321 as the leading zeros are not retained. Given an integer num, reverse num to get reversed1, then reverse reversed1 to get reversed2. Return true if reversed2 equals num. Otherwise return false.

Example 1:

Input: num = 526
Output: true
Explanation: Reverse num to get 625, then reverse 625 to get 526, which equals num.

Example 2:

Input: num = 1800
Output: false
Explanation: Reverse num to get 81, then reverse 81 to get 18, which does not equal num.

Example 3:

Input: num = 0
Output: true
Explanation: Reverse num to get 0, then reverse 0 to get 0, which equals num.

Constraints:

`0 <= num <= 106``

Common Issues and Mastering Effective Debugging Techniques

Mon, 21 Aug 2023 06:00:00 +0400

While Kubernetes offers a powerful platform for deploying containerized applications, managing complex clusters can sometimes lead to challenges and errors. In this comprehensive blog post, we will delve into common issues that arise in Kubernetes clusters and equip you with effective troubleshooting and debugging methodologies. By the end, you’ll be empowered to unravel the mysteries of Kubernetes troubleshooting and confidently resolve issues to ensure the seamless operation of your clusters.

K8s CI/CD: GitOps with Jenkins, GitLab, Argo CD

Sun, 20 Aug 2023 06:00:00 +0400

Continuous Integration and Continuous Deployment (CI/CD) pipelines are fundamental to the success of Kubernetes deployments, enabling fast and reliable application delivery. In this comprehensive blog post, we will explore CI/CD pipelines customized for Kubernetes, including the GitOps approach, and how to leverage popular tools like Jenkins, GitLab, and Argo CD. By the end, you’ll be equipped with actionable insights to build efficient CI/CD pipelines that seamlessly integrate with your Kubernetes ecosystem.

K8s Monitoring & Logging: Best Practices & Top Tools

Sat, 19 Aug 2023 06:00:00 +0400

Monitoring and logging are critical components of a successful Kubernetes deployment, providing insights into the health, performance, and behavior of your clusters and applications. In this comprehensive blog post, we will cover best practices for monitoring Kubernetes, including node and pod metrics, as well as exploring popular monitoring and logging tools such as Prometheus, Grafana, and Elasticsearch. By the end, you’ll be equipped with actionable knowledge to set up robust observability for your Kubernetes ecosystem, enabling you to detect issues proactively and ensure smooth operations.

K8s Upgrades & Rollbacks Guide to Compatibility & Strategies

Fri, 18 Aug 2023 06:00:00 +0400

Keeping your Kubernetes cluster up-to-date is crucial for security, performance, and accessing the latest features. However, orchestrating Kubernetes upgrades and rollbacks can be a challenging endeavor. In this all-encompassing blog post, we will dive into the complexities of Kubernetes upgrades, exploring version compatibility considerations, the power of rolling updates, and the importance of robust rollback strategies. By the end, you’ll be equipped with actionable insights to navigate Kubernetes upgrades and rollbacks with confidence, ensuring your cluster remains resilient and always up-to-date.

K8s Pod Scheduling: Node & Pod Affinity Demystified

Thu, 17 Aug 2023 06:00:00 +0400

Efficient pod scheduling is essential to achieving high performance and resource utilization in a Kubernetes cluster. Understanding the intricacies of pod scheduling, particularly node affinity, pod affinity, and anti-affinity rules, empowers you to distribute workloads effectively. In this comprehensive blog post, we will explore the art of pod scheduling in Kubernetes, shedding light on the power of node affinity, enhancing resource allocation with pod affinity, and ensuring fault tolerance through anti-affinity. By the end, you’ll be equipped to fine-tune pod placement and optimize the distribution of workloads within your Kubernetes ecosystem.

Securing Kubernetes: Guarding Against Container Threats

Wed, 16 Aug 2023 06:00:00 +0400

Kubernetes has become the de facto platform for deploying containerized applications, revolutionizing software development. However, with great power comes great responsibility, and security is paramount in a Kubernetes environment. In this comprehensive blog post, we will delve into the critical security concerns in Kubernetes, covering the protection of the API server, implementing Role-Based Access Control (RBAC), fortifying with Network Policies, and mitigating container vulnerabilities. By the end, you’ll have actionable tips to build a robust Kubernetes fortress, protecting your applications and data from potential security risks.

K8s Cluster Performance: Resource Optimization Guide

Tue, 15 Aug 2023 06:00:00 +0400

Efficiently managing resources in a Kubernetes cluster is crucial to achieving peak performance and cost-effectiveness. Resource allocation, utilization, and handling resource-intensive applications demand careful consideration. In this comprehensive blog post, we will delve into best practices for resource management, exploring resource allocation techniques, monitoring, and optimizing resource-hungry applications. By the end, you’ll be armed with the knowledge to optimize your Kubernetes cluster for maximum productivity and resource efficiency.

Understanding Resource Management in Kubernetes

Resource management involves allocating CPU, memory, and other resources to applications running in a Kubernetes cluster. Properly managing these resources ensures that applications receive the necessary compute power while avoiding resource contention that can lead to performance bottlenecks.

K8s Scaling Mastery: Manual, HPA & Metrics APIs

Mon, 14 Aug 2023 06:00:00 +0400

Kubernetes has revolutionized application deployment by providing a scalable and efficient container orchestration platform. However, as your applications grow, you’ll encounter the challenge of efficiently scaling them to meet varying demands. In this in-depth blog post, we will explore the intricacies of scaling applications in Kubernetes, discussing manual scaling, Horizontal Pod Autoscalers (HPA), and harnessing the power of Kubernetes Metrics APIs. By the end, you’ll be equipped with the knowledge to elegantly scale your applications, ensuring they thrive under any workload.

K8s Storage Demystified: Persistent Volumes & Classes

Sun, 13 Aug 2023 06:00:00 +0400

Kubernetes has become the go-to platform for deploying scalable, containerized applications. However, managing persistent data in a dynamic container environment presents unique challenges. In this comprehensive blog post, we’ll delve into the world of Kubernetes persistent storage, exploring the various approaches like Persistent Volumes (PVs) and Storage Classes (SCs). We’ll also shed light on common issues such as data loss and performance bottlenecks, equipping you with the knowledge to ensure data integrity and optimal storage performance within your Kubernetes clusters.

K8s Networking: Pod Communication and Ingress Demystified

Sat, 12 Aug 2023 06:00:00 +0400

Kubernetes has revolutionized the way we deploy and manage containerized applications. However, with the increasing complexity of distributed systems, networking and communication between pods within a Kubernetes cluster can become a daunting challenge. In this blog post, we will delve into the common networking issues that arise in Kubernetes and explore effective solutions using Service Discovery and Ingress controllers. By the end, you’ll have a clearer understanding of how to ensure seamless communication between your pods, enabling your applications to thrive in the Kubernetes ecosystem.

React State Balancing: A Guide to State Management

Fri, 11 Aug 2023 06:00:00 +0400

As React apps grow, managing shared and app-wide state can become challenging. Dedicated state management libraries help tackle these complexities.

Let’s compare popular options:

Redux

Redux uses a centralized store for state:

// Store with root reducer
const store = createStore(rootReducer);

// Dispatch actions  
store.dispatch(addTodo(text));

// Selectors
const todos = useSelector(state => state.todos);

Redux enforces unidirectional data flow inspired by functional programming.

MobX

MobX uses observable variables that update reactively:

// Observable store
const store = observable({
  todos: []
});

// Computed values derived from store 
const completedTodos = computed(() => {
  return store.todos.filter(todo => todo.complete);
});

MobX automatically tracks dependencies and re-renders on changes.

React + Node: Beginner's Guide to Full Stack Dev

Thu, 10 Aug 2023 06:00:00 +0400

React excels at building fast, dynamic frontends. Node.js shines for server-side APIs and microservices. Together, they make a powerful stack for full stack apps.

Let’s walk through integrating React with Node.js:

Serving React Builds

Use Node.js middleware like Express to serve the React app:

// server.js
app.use(express.static(path.join(__dirname, 'client/build')));

app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'client/build', 'index.html));
});

This serves the React build from the /build folder.

Proxying API Requests

Proxy frontend requests to the backend API:

Optimal React Patterns: Beginner's Guide

Wed, 09 Aug 2023 06:00:00 +0400

As with any framework, React comes with its own set of best practices and optimal patterns. Let’s explore some tips for writing robust React code:

Modular Components

Break components into reusable, composable units:

// Bad
function App() {
  return (
    <header>
      <nav>
        <logo>
        <links>
      </nav>
      
      <h1>Welcome!</h1>
      
      <footer>
        <copyright>
      </footer>
    </header>
  );
}

// Good
function Nav() {
  return (
    <nav>
      <Logo />
      <Links />
    </nav>
  ); 
}

function Header() {
  return (
    <header>
      <Nav />
      <h1>Welcome!</h1>
      <Footer />
    </header>
  );
}

This encourages reusability.

Debugging React Apps: Beginner's Guide

Tue, 08 Aug 2023 06:00:00 +0400

Bugs are inevitable in complex React applications. Thankfully, React provides great tools to squash bugs quickly.

Let’s look at some key techniques for debugging React apps:

React Developer Tools

The React DevTools Chrome extension lets you inspect React component hierarchies, props, state and more in Chrome:

DevTools:

<App>
  <Navbar />   
  <Profile 
    name="Jane"
    imageUrl="https://..." 
  />
</App>

This provides invaluable visibility into React apps.

Error Boundaries

Error boundaries catch errors and display fallbacks:

Go WebAssembly: High-Performance Web Applications

Tue, 08 Aug 2023 00:00:00 +0000

Build high-performance web applications using Go and WebAssembly with advanced optimization techniques and JavaScript interoperability.

Understanding the Foundation

WebAssembly represents a fundamental shift in web development capabilities. For years, JavaScript was the only option for client-side computation, which worked fine for most applications but hit performance walls with computationally intensive tasks like data processing, image manipulation, or complex algorithms.

WebAssembly changes this by allowing languages like Go, Rust, and C++ to run in the browser at near-native speeds. This opens up possibilities that were previously impossible or impractical in web applications—real-time data processing, complex simulations, and performance-critical applications that would have required desktop software.

Advanced React Patterns: Compound Components & More

Mon, 07 Aug 2023 06:00:00 +0400

As React apps scale, you’ll want to structure components for greater reusability and composability. Here are some powerful React patterns:

Compound Components

The compound components pattern creates component APIs with shared context:

// Parent exposes context through 'Box' component
function Layout({children}) {
  return <Box>{children}</Box>
}

// Children access shared context via Box
function Profile() {
  return (
    <Layout>
      <Box p={2}>
        <h1>Jane Doe</h1>
      </Box>
    </Layout>
  );
}

This provides more flexible APIs than just props.

React Animation Guide: Libraries and Techniques

Sun, 06 Aug 2023 06:00:00 +0400

Animation brings interfaces to life. Thankfully, React has great open source libraries for animation. Let’s compare some popular options:

Framer Motion

Framer Motion uses declarative props for animation:

import { motion } from 'framer-motion';

const boxVariants = {
  hidden: { opacity: 0 },
  visible: { opacity: 1 }, 
}

function MyComponent() {
  return (
    <motion.div 
      initial="hidden"
      animate="visible"
      variants={boxVariants}
    />
  );
}

Framer Motion allows CSS, SVG, gesture, and physics animations.

React Transition Group

React Transition Group offers class-based transitions:

Testing React Apps: Beginner's Guide to TDD

Sat, 05 Aug 2023 06:00:00 +0400

Testing is crucial for ensuring React apps are stable and bug-free. Popular tools like Jest and React Testing Library make testing React components simple.

Let’s look at how to write great tests for React:

render Component

Render the component into a test environment using render from React Testing Library:

import { render } from '@testing-library/react';
import Button from './Button';

test('displays button text', () => {
  const { getByText } = render(<Button>Click</Button>);
  
  expect(getByText('Click')).toBeInTheDocument(); 
});

This renders the component virtually for testing.

Data Fetched Fast - A Beginner's Guide to React Query

Fri, 04 Aug 2023 06:00:00 +0400

Fetching data in React often means using stale state and complex caching logic.

React Query simplifies data fetching with powerful features like automatic caching, deduplication, and background updates.

Let’s explore some key features of React Query:

Declarative Data Fetching

Fetch data with the useQuery hook:

import { useQuery } from 'react-query';

function MyComponent() {
  const { data, error, isLoading } = useQuery('posts', fetchPosts);
  
  // use data  
}

useQuery handles declaring cache keys, performing fetches, and more.

background Refetching

React Query automatically refetches “inactive” queries in the background:

Forms Simplified, A Beginner's Guide to Managing React Forms

Thu, 03 Aug 2023 06:00:00 +0400

Forms are a common need for many React apps. However, managing form state and validation can be tricky.

Thankfully, React provides great libraries to simplify complex forms. Let’s explore some helpful tools:

Formik for Form State

Formik handles common form tasks:

import { Formik } from 'formik';

const MyForm = () => (
  <Formik
    initialValues={{ email: '' }}
    onSubmit={values => console.log(values)}
  >
    {formik => (
      <form onSubmit={formik.handleSubmit}>
        <input 
          name="email"
          onChange={formik.handleChange}
          value={formik.values.email} 
        />
        <button type="submit">Submit</button>
      </form>
    )}
  </Formik>
)

Formik reduces boilerplate for:

Go Performance Profiling and Optimization

Thu, 03 Aug 2023 00:00:00 +0000

Master Go’s profiling tools.

Understanding Go Performance Fundamentals

Before diving into specific profiling tools, it’s essential to understand the key factors that influence Go application performance and the metrics that matter most when optimizing.

Performance Metrics and Objectives

Performance optimization should always begin with clear objectives and metrics:

package main

import (
	"fmt"
	"time"
)

// PerformanceMetrics tracks key performance indicators
type PerformanceMetrics struct {
	Latency       time.Duration // Time to complete a single operation
	Throughput    int           // Operations per second
	MemoryUsage   uint64        // Bytes allocated
	CPUUsage      float64       // CPU utilization percentage
	GCPause       time.Duration // Garbage collection pause time
	ResponseTime  time.Duration // Time to first byte (for servers)
	ErrorRate     float64       // Percentage of operations that fail
	SaturationPoint int         // Load at which performance degrades
}

// Example performance objectives for different application types
func definePerformanceObjectives() {
	// Low-latency trading system
	tradingSystemObjectives := PerformanceMetrics{
		Latency:       100 * time.Microsecond, // 99th percentile
		Throughput:    100000,                 // 100K trades per second
		MemoryUsage:   1 * 1024 * 1024 * 1024, // 1GB max heap
		CPUUsage:      80.0,                   // 80% max CPU utilization
		GCPause:       1 * time.Millisecond,   // 1ms max GC pause
		ErrorRate:     0.0001,                 // 0.01% max error rate
		SaturationPoint: 120000,               // Handles 20% over target load
	}

	// Web API service
	webAPIObjectives := PerformanceMetrics{
		Latency:       50 * time.Millisecond,  // 99th percentile
		Throughput:    5000,                   // 5K requests per second
		MemoryUsage:   2 * 1024 * 1024 * 1024, // 2GB max heap
		ResponseTime:  20 * time.Millisecond,  // 20ms time to first byte
		ErrorRate:     0.001,                  // 0.1% max error rate
		SaturationPoint: 7500,                 // Handles 50% over target load
	}

	// Batch processing system
	batchProcessingObjectives := PerformanceMetrics{
		Throughput:    10000,                  // 10K records per second
		MemoryUsage:   8 * 1024 * 1024 * 1024, // 8GB max heap
		CPUUsage:      95.0,                   // 95% max CPU utilization
		ErrorRate:     0.0005,                 // 0.05% max error rate
	}

	fmt.Printf("Trading system 99th percentile latency target: %v\n", 
		tradingSystemObjectives.Latency)
	fmt.Printf("Web API throughput target: %v requests/second\n", 
		webAPIObjectives.Throughput)
	fmt.Printf("Batch processing memory usage target: %v bytes\n", 
		batchProcessingObjectives.MemoryUsage)
}

Performance Bottleneck Categories

Understanding the different types of bottlenecks helps guide your profiling approach:

Optimizing React Performance: Beginner's Guide

Wed, 02 Aug 2023 06:00:00 +0400

As React apps grow, you may notice performance starting to lag - sluggish interactions, choppy animations, janky scrolling.

Luckily, there are many great techniques to optimize React app performance. Let’s look at some top tips:

Use React.memo for Component Memoization

The React.memo API can memoize component outputs:

const MyComponent = React.memo(function MyComponent(props) {
  /* only rerenders if props change */
});

This prevents unnecessary re-renders if props stay the same.

Virtualize Long Lists

Rendering thousands of rows kills performance. Virtualize rendering instead:

State Management 101 - A Beginner's Guide to React State

Tue, 01 Aug 2023 06:00:00 +0400

State management is a crucial concept in React. State allows components to dynamically update UI based on data changes.

However, managing state properly takes some practice. Let’s walk through the basics of handling state in React:

Creating State

The useState hook defines state variables:

import { useState } from 'react';

function Example() {
  const [count, setCount] = useState(0);
}

useState accepts the initial state value and returns:

The current state
A function to update it

Reading State

To display state in UI, simply reference the variable:

Accessible React Apps: Beginner's Guide to Accessibility

Mon, 31 Jul 2023 06:00:00 +0400

Accessibility is an important consideration when building modern web apps. React provides useful tools to make accessible, inclusive products.

Let’s look at some best practices for web accessibility with React:

Semantic HTML

Use proper HTML semantics. For example:

// Good
<button>Save</button>

// Avoid 
<div onclick="save">Save</div>

Semantic HTML is parsed correctly by screen readers.

alt Text

Images should have alt text describing content/purpose:

<img src="logo.png" alt="Company logo" />

Screen readers can’t interpret images. alt text substitutes meaning.

Mystery Boxes - A Beginner's Guide to React Fragments

Sun, 30 Jul 2023 06:00:00 +0400

When returning multiple elements from a component’s render method, they must be wrapped in a single parent DOM node:

// Needs a <div> wrapper
return (
  <div> 
    <ChildA />
    <ChildB />
  </div>
);

This extra wrapper <div> in the DOM is often unwanted. Enter React fragments - a way to group elements without adding extra nodes.

Short Syntax

The simplest fragment syntax is:

return (
  <>
    <ChildA />
    <ChildB />
  </>
);

The <></> syntax declares a React fragment. Fragments let you skip the wrapper <div>.

Unidirectional Data Flow in React: Beginner's Guide

Sat, 29 Jul 2023 06:00:00 +0400

A key advantage of React is its unidirectional data flow. This makes the flow of data predictable, and helps avoid unexpected side effects from data changing unexpectedly.

But what exactly does “unidirectional data flow” mean in React? Let’s break it down:

The Data Flows Down

In React, parent components pass data to children via props:

// Parent
function Parent() {
  const [value, setValue] = useState('Hello');

  return <Child value={value} />; 
}

// Child
function Child({value}) {
  return <h1>{value}</h1>;
}

The parent’s value state is passed down into the Child via a prop. This is the “data down” part.

Advanced Go Channel Patterns: Mastering Communication in Concurrent Systems

Sat, 29 Jul 2023 00:00:00 +0000

Explore sophisticated channel patterns that enable elegant, efficient communication between goroutines in complex concurrent applications.

#Channels are Go’s primary tool for goroutine communication. Most developers know the basics - sending and receiving values - but advanced patterns unlock much more powerful concurrent designs.

Beyond Basic Channels

Basic channel operations are straightforward:

ch := make(chan int)
go func() { ch <- 42 }()
value := <-ch

But real systems need more sophisticated coordination:

Pipeline Processing: Chain operations together
Fan-Out/Fan-In: Distribute work and collect results
Rate Limiting: Control operation flow
Timeouts: Handle operations that take too long
Cancellation: Stop work when it’s no longer needed

Common Channel Pitfalls

Before diving into patterns, understand the traps:

Event Handling in React: Beginner's Guide

Fri, 28 Jul 2023 06:00:00 +0400

Responding to user events is a crucial part of building interactive UIs. In React, you can pass event handlers as props to components to run code when events occur.

Let’s look at how to listen and react to common events in React:

Binding to Events

Pass an event handler function to a component to subscribe to events:

function Button({ onClick }) {
  return (
    <button onClick={onClick}>
      Click Me
    </button>
  );
}

function App() {
  const handleClick = () => {
    console.log('Clicked!');
  };

  return (
    <Button onClick={handleClick} />
  );
}

When the button is clicked, handleClick will be called.

Circuit Breaker Patterns in Go

Fri, 28 Jul 2023 00:00:00 +0000

Implement robust circuit breaker patterns in Go for building resilient microservices that handle failures gracefully and prevent cascade failures.

Understanding Circuit Breaker Patterns

Before diving into implementation details, it’s crucial to understand the core concepts behind circuit breakers and how they fit into a broader resilience strategy.

The Circuit Breaker State Machine

At its core, a circuit breaker is a state machine with three distinct states:

package circuitbreaker

// State represents the current state of the circuit breaker
type State int

const (
    // Closed means the circuit breaker is allowing requests through
    Closed State = iota
    
    // Open means the circuit breaker is preventing requests from going through
    Open
    
    // HalfOpen means the circuit breaker is allowing a limited number of test requests
    HalfOpen
)

// CircuitBreaker represents a basic circuit breaker
type CircuitBreaker struct {
    state           State
    failureCount    int
    failureThreshold int
    resetTimeout    time.Duration
    lastFailureTime time.Time
    mutex           sync.RWMutex
}

The circuit breaker operates as follows:

Hooked on React - A Beginner's Guide to React Hooks

Thu, 27 Jul 2023 06:00:00 +0400

When React was first released, class components were the standard way to build complex UIs. However, classes can be cumbersome for some use cases.

Enter React hooks - a way to use React features like state and lifecycle methods without classes.

Hooks provide a more direct API for React concepts you already know. Let’s dive into some commonly used hooks:

Managing State with useState

The useState hook lets components use state without a class:

Lifting State in React: Beginner's Guide

Wed, 26 Jul 2023 06:00:00 +0400

As React apps grow in complexity, managing shared state between components can become tricky. Oftentimes, several child components may need to reflect the same data in the UI.

The React solution is to lift the state up to a common ancestor component. The parent component can manage the state, and pass it down to the children via props.

Let’s look at how to lift state for easier data sharing:

The Problem with Local State

Imagine we have a <Toolbox> component that contains some <Tool> components:

Looping in JSX with React Keys: Beginner's Guide

Tue, 25 Jul 2023 06:00:00 +0400

Looping over arrays to render lists of elements is a common need in React apps. However, there are some special considerations when rendering lists in JSX.

One important aspect is the key prop. React uses keys to uniquely identify list elements and optimize performance.

Let’s look at how to loop through arrays in JSX, and why keys are important:

Rendering Arrays in JSX

JSX makes looping straightforward - you can use JavaScript’s map() function directly:

Conditional Rendering in React

Mon, 24 Jul 2023 06:00:00 +0400

In React apps, you’ll often need to render different UI components conditionally based on certain state. For example, showing a login form if a user is not authenticated, or displaying different content based on configurable settings.

Here are useful patterns for conditional rendering in React:

If/Else Statements

The standard JS if/else statement works in JSX too:

function App() {
  const loggedIn = false;
  
  if (loggedIn) {
    return <WelcomeMessage />;
  } else {
    return <LoginForm />;
  }
}

This will render either the WelcomeMessage or LoginForm component based on the value of loggedIn.

Passing Data Between React Components with Props

Sun, 23 Jul 2023 06:00:00 +0400

One of React’s core concepts is reusability through composable components. Components allow splitting complex UI into separate, reusable pieces. However, for components to communicate, they need a way to pass data to each other. Enter props.

Props allow passing data from a parent component to a child component. They are like function parameters, but for React components.

Let’s look at a simple example:

// Parent component
const Parent = () => {
  return (
    <Child 
      color="blue"
      onClick={handleClick} 
    />
  );
}

// Child component
const Child = (props) => {
  return <div>{props.color}</div> 
}

The parent component Parent passes two props to the child component Child - a color string and an onClick event handler.

Fostering DevOps Learning Culture: Lifelong Learning

Sat, 22 Jul 2023 06:00:00 +0400

Introduction

In the fast-evolving world of technology, where advancements and innovations are a constant, staying ahead of the curve is paramount for any DevOps team. One of the most effective ways to achieve this is by fostering a continuous learning culture. Embracing a mindset of lifelong learning not only empowers individuals to enhance their skills and knowledge but also drives collective growth and innovation within the organization. In this blog post, we will explore the significance of building a continuous learning culture in DevOps, its impact on team performance, and practical strategies to implement and sustain such a culture. Join us on this journey as we discover how to unleash the power of continuous learning in DevOps.

DevOps' Role in AI: Enhancing Intelligent Systems

Fri, 21 Jul 2023 06:00:00 +0400

Introduction

The world of technology is witnessing a remarkable fusion of two transformative disciplines: DevOps and Artificial Intelligence (AI). DevOps has revolutionized software development, emphasizing collaboration, automation, and continuous delivery, while AI has pushed the boundaries of what machines can achieve, enabling intelligent decision-making and automation. In this blog post, we will explore the symbiotic relationship between DevOps and AI, the challenges and opportunities it presents, and how organizations can leverage this powerful combination to unlock the full potential of intelligent systems. Join us on this journey as we delve into the role of DevOps in the realm of Artificial Intelligence.

DevOps and Microservices: Scalable, Agile Software Delivery

Thu, 20 Jul 2023 06:00:00 +0400

Introduction

In the fast-paced world of software development, two crucial methodologies have emerged as game-changers for modern development teams: DevOps and Microservices. DevOps is a cultural and technical movement that emphasizes collaboration, automation, and continuous delivery, while Microservices is an architectural style that structures applications as a collection of loosely coupled, independently deployable services. Combining these methodologies can empower organizations to achieve scalable, agile, and efficient software delivery. In this blog post, we will explore the intersection of DevOps and Microservices, their synergies, and how they complement each other. Additionally, we will dive into practical examples with code to demonstrate their seamless integration.

Nature-Inspired Problem Solving: Genetic Algorithms

Wed, 19 Jul 2023 06:00:00 +0400

Introduction

Genetic Algorithms (GAs) and Evolutionary Computation (EC) are powerful optimization techniques inspired by the process of natural selection and evolution. These algorithms mimic the principles of genetics and survival of the fittest to find high-quality solutions to complex problems. In this blog post, we will dive into the world of Genetic Algorithms and Evolutionary Computation, exploring their underlying concepts and demonstrating how they can be implemented in Python to tackle a variety of real-world challenges.

Python Dynamic Programming: Mastering Optimization

Tue, 18 Jul 2023 06:00:00 +0400

Introduction

Dynamic programming is a powerful algorithmic technique that allows developers to tackle complex problems efficiently. By breaking down these problems into smaller overlapping subproblems and storing their solutions, dynamic programming enables the creation of more adaptive and resource-efficient solutions. In this comprehensive guide, we will explore dynamic programming in-depth and learn how to apply it in Python to solve a variety of problems.

1. Understanding Dynamic Programming

Dynamic programming is a method of solving problems by breaking them down into smaller, simpler subproblems and solving each subproblem only once. The solutions to subproblems are stored in a data structure, such as an array or dictionary, to avoid redundant computations. Dynamic programming is particularly useful when a problem exhibits the following characteristics:

Python Reflection & Metaprogramming: Advanced Power

Mon, 17 Jul 2023 06:00:00 +0400

Introduction

Python is a versatile programming language that offers powerful features and capabilities. For advanced users, understanding and harnessing the potential of reflection and metaprogramming can open up a whole new world of possibilities. In this blog post, we’ll dive deep into the concepts of reflection and metaprogramming in Python, exploring their definitions, use cases, and implementation techniques. By mastering reflection and metaprogramming, you can build resilient, scalable, and highly adaptable applications. Get ready to elevate your Python skills as we unravel the magic of reflection and metaprogramming!

Go Context Patterns: Advanced Request Lifecycle Management

Mon, 17 Jul 2023 00:00:00 +0000

Master advanced Go context patterns for sophisticated request lifecycle management, cancellation, and deadline handling in concurrent applications.

Context Fundamentals

Why Context Matters More Than You Think

When I first encountered Go’s context package, I’ll be honest—I thought it was just another way to pass around cancellation signals. Boy, was I wrong. After years of debugging production issues and watching teams struggle with request lifecycle management, I’ve come to realize that context is actually the backbone of well-architected Go applications.

Kubernetes ReplicaSets: Scalability & Fault Tolerance

Sun, 16 Jul 2023 06:00:00 +0400

Introduction

In Kubernetes, ReplicaSets are a vital resource that enables scalable and fault-tolerant deployments of pods. They provide the ability to ensure a desired number of pod replicas are running at all times, allowing applications to handle increased traffic and recover from failures. In this blog post, we will delve into the world of ReplicaSets, exploring their functionalities, use cases, and best practices. By mastering ReplicaSets, you can build resilient and scalable deployments in Kubernetes.

Kubernetes Namespaces: Isolation & Resource Management

Sat, 15 Jul 2023 06:00:00 +0400

Introduction

In Kubernetes, namespaces provide a powerful abstraction that allows you to partition and isolate resources within a cluster. In this blog post, we’ll explore Kubernetes namespaces in detail and discuss their importance in achieving effective resource management and isolation. By understanding namespaces and leveraging their capabilities, you can enhance the security, scalability, and manageability of your Kubernetes deployments. Let’s dive into the world of namespaces and unlock their potential!

Understanding Kubernetes Namespaces

Kubernetes namespaces provide a virtual clustering mechanism that allows you to divide a cluster into multiple logical units. Each namespace acts as a separate virtual cluster, providing isolation and resource segmentation. This ensures that resources within a namespace are isolated from resources in other namespaces, providing a boundary for managing applications and their associated components.

K8s Cluster Resiliency: Advanced High Availability

Fri, 14 Jul 2023 06:00:00 +0400

Introduction

In today’s technology landscape, ensuring the resiliency and high availability of Kubernetes clusters is crucial for maintaining the availability of applications and business continuity. In this blog post, we will explore advanced techniques and best practices for building cluster resiliency in Kubernetes. By implementing these strategies, you can ensure that your applications remain highly available, even in the face of failures or disruptions. Let’s dive into the world of cluster resiliency and learn how to build rock-solid, resilient clusters!

K8s Networking Mastery: Advanced Cluster Communication

Thu, 13 Jul 2023 06:00:00 +0400

Introduction

Kubernetes has revolutionized container orchestration, enabling the efficient management of complex applications. As an advanced user, you’re likely already familiar with the basics of Kubernetes networking. In this blog post, we’ll dive deeper into advanced networking concepts, exploring techniques and best practices to optimize cluster communication, enhance security, and troubleshoot network-related issues. Get ready to level up your networking skills in Kubernetes!

Network Models in Kubernetes

In Kubernetes, network models play a crucial role in facilitating communication between pods. One commonly used model is the overlay network. This model allows pods to communicate seamlessly across different nodes by encapsulating network packets within an overlay network. Understanding how overlay networks work and how they enable efficient pod-to-pod communication is essential for advanced networking in Kubernetes.

Blue-Green Deployments in Kubernetes: Production & DR

Wed, 12 Jul 2023 06:00:00 +0400

Introduction

In today’s fast-paced and highly competitive digital landscape, organizations strive to deliver seamless and uninterrupted services to their customers. To achieve this, a robust production strategy combined with a solid disaster recovery (DR) plan is crucial. In the realm of Kubernetes, one powerful technique for achieving these goals is the implementation of blue-green deployments. This blog post will explore the concept of blue-green deployments, their benefits, and how they can be effectively leveraged in Kubernetes environments to streamline production and disaster recovery strategies.

AWS Production-DR Failover: Advanced Strategies

Tue, 11 Jul 2023 06:00:00 +0400

Introduction

Implementing failover between a production (Prod) account and a disaster recovery (DR) account is a critical aspect of ensuring high availability and business continuity in AWS. While DNS-based failover is a common approach, advanced users can explore additional strategies that provide enhanced control, automation, and scalability for failover scenarios. In this comprehensive guide, we will delve into advanced techniques that go beyond DNS, enabling advanced users to build robust failover architectures in AWS.

Python Context Managers Mastery: Resource Management

Mon, 10 Jul 2023 06:00:00 +0400

Introduction

Python context managers provide a convenient and reliable way to manage resources and ensure proper setup and teardown actions. Whether dealing with file operations, database connections, or any resource that needs to be acquired and released, context managers offer a clean and concise approach. This comprehensive blog post will explore the concept of context managers in Python, starting from the fundamentals and gradually progressing to more advanced techniques.

Understanding Context Managers

The Context Management Protocol

The Context Management Protocol defines the interface that objects must implement to be used as context managers. It requires the implementation of __enter__() and __exit__() methods. The __enter__() method sets up the context, while the __exit__() method handles the cleanup actions.

Python Decorators Mastery: Advanced Usage Guide

Sun, 09 Jul 2023 06:00:00 +0400

Introduction

Python decorators are a powerful feature that allows you to modify the behavior of functions or classes dynamically. Decorators provide a way to add functionality to existing code without modifying the original source. This blog post will delve into the concept of decorators in Python, starting from the basics and gradually progressing to more advanced techniques.

Understanding Decorators

Function Decorators

Function decorators are a way to modify the behavior of a function by wrapping it inside another function. The decorator function takes the original function as an argument, adds some functionality, and returns a modified function. This allows you to enhance or extend the behavior of functions without modifying their source code.

Python's Yield Mastery: Advanced Usage Guide

Sat, 08 Jul 2023 06:00:00 +0400

Introduction

Python’s yield statement is a powerful feature that allows you to create generator functions. Generators provide an efficient way to generate a sequence of values without storing them all in memory at once. This blog post will delve into the concept of yield in Python, starting from the basics and gradually progressing to more advanced techniques.

Understanding the Basics

Yield vs. Return

In Python, the yield statement is used within a function to create a generator. Unlike the return statement, which terminates the function and returns a single value, yield allows the function to produce a sequence of values, one at a time. This is what differentiates generator functions from regular functions.

Python: Unleashing the Power of Simplicity and Versatility

Fri, 07 Jul 2023 06:00:00 +0400

Getting Started with Python

Python is a versatile and popular programming language known for its simplicity and readability. It is widely used in various fields, including web development, data analysis, artificial intelligence, and automation. If you’re new to Python, this guide will help you get started with the basics and provide some code examples to illustrate key concepts.

Installing Python

To begin, you need to install Python on your computer. Python is available for multiple platforms, including Windows, macOS, and Linux. You can download the latest version of Python from the official website (https://www.python.org/downloads/) and follow the installation instructions specific to your operating system.

Python's Advanced Features: Empowering Programmers

Thu, 06 Jul 2023 06:00:00 +0400

Introduction:

In the vast realm of programming, Python stands tall as a language that caters to developers of all levels. Beyond its beginner-friendly syntax, Python harbors a treasure trove of advanced features that can elevate your coding prowess to new heights. In this blog post, we embark on an exhilarating journey to explore the depths of Python’s advanced features, unleashing their full potential. Brace yourself as we delve into the world of decorators, context managers, metaclasses, multiple inheritance, generators, coroutines, dynamic typing, duck typing, and functional programming tools. Get ready to unlock the true power of Python!

Advanced Go Testing Strategies and Benchmarking

Thu, 06 Jul 2023 00:00:00 +0000

Master comprehensive testing approaches in Go including unit testing.

#In the world of Go development, writing code is only half the battle. The other half—often more challenging and equally critical—is ensuring that your code works correctly, performs efficiently, and remains resilient under all conditions. As Go continues to power mission-critical systems across industries, from financial services to cloud infrastructure, the importance of comprehensive testing strategies cannot be overstated.

This guide explores advanced testing techniques that go beyond basic unit tests to help you build truly bulletproof Go applications. We’ll dive deep into sophisticated testing patterns, benchmarking strategies, and quality assurance practices that experienced Go developers use to ensure their systems perform reliably at scale.

Python's Yield: Unleashing Generator Magic

Wed, 05 Jul 2023 06:00:00 +0400

Introduction

Python, being a versatile language, offers numerous tools and features to streamline our coding experience. One such powerful feature is the yield keyword. In this blog post, we will embark on an exciting journey to explore the hidden potential of Python’s yield statement and dive into the realm of generators. Buckle up and get ready to witness the magic unfold!

Section 1: Understanding the Basics of Yield

At its core, yield is used in Python to create generator functions. Generators are special functions that can pause and resume their execution, allowing us to iterate over a sequence of values without creating them all at once. Let’s take a look at a simple example to grasp the concept:

GitOps Rising: Transforming DevOps for Streamlined Delivery

Tue, 04 Jul 2023 06:00:00 +0400

Introduction

In today’s fast-paced digital landscape, where businesses strive to deliver high-quality software products with agility and efficiency, DevOps practices have become indispensable. DevOps aims to bridge the gap between software development and operations, enabling seamless collaboration, faster deployments, and improved overall software delivery. One of the most prominent trends revolutionizing the DevOps world is GitOps. In this blog post, we will explore the concept of GitOps, its benefits, and why it has gained significant traction in the industry.

Enhancing Security: How DevOps Mitigates Cyber Threats

Mon, 03 Jul 2023 06:00:00 +0400

Introduction

In today’s digital landscape, where cyber threats are prevalent and evolving, organizations must adopt robust security measures to safeguard their sensitive data and systems. In this pursuit, DevOps practices have emerged as a powerful ally, enabling organizations to build secure and resilient software solutions. By integrating security into every stage of the software development lifecycle, DevOps plays a crucial role in preventing, detecting, and responding to cyber attacks. In this blog post, we will explore how DevOps helps organizations fend off hackers and enhance their overall security posture.

Site Reliability Engineering (SRE) in Modern Organizations

Sun, 02 Jul 2023 06:00:00 +0400

Introduction

In today’s fast-paced and technology-driven world, organizations heavily rely on digital services to deliver their products and serve their customers. With the increasing complexity of modern infrastructure and the need for high availability and reliability, Site Reliability Engineering (SRE) has emerged as a critical discipline. SRE combines software engineering principles with operations expertise to ensure the smooth functioning of complex systems. In this blog post, we will explore the importance of SRE in organizations and how it contributes to their success.

DevOps & DevSecOps: Bridging Dev-Security Gap

Sat, 01 Jul 2023 06:00:00 +0400

Introduction

In today’s fast-paced digital landscape, where software development cycles are becoming increasingly rapid and security threats are ever-present, organizations are seeking effective ways to align development and security practices. Two prominent approaches that have gained significant attention are DevOps and DevSecOps. While these terms may sound similar, there are crucial distinctions between them. In this blog post, we will explore the differences between DevOps and DevSecOps, their goals, and how they contribute to efficient and secure software delivery.

Unleashing the Power: Lambda - A Killer Feature in AWS

Fri, 30 Jun 2023 06:00:00 +0400

In the world of cloud computing, Amazon Web Services (AWS) has long been a dominant player, providing a comprehensive suite of services to meet the diverse needs of businesses. Among its vast array of offerings, one particular service stands out as a true game-changer: AWS Lambda. Lambda is a serverless computing platform that has revolutionized the way developers build and deploy applications. In this blog post, we’ll explore why Lambda is rightly hailed as a killer feature in AWS.

Python vs Java Performance: Programming Powerhouses

Thu, 29 Jun 2023 06:00:00 +0400

In the vast landscape of programming languages, Python and Java have emerged as titans, offering robust solutions for a wide range of applications. When it comes to performance, developers often find themselves pondering which language reigns supreme. In this blog post, we will delve into the world of Python and Java, exploring their performance characteristics, strengths, and weaknesses, and ultimately helping you make an informed choice for your next project.

Teach me the Basics of Data Science in Python

Wed, 28 Jun 2023 06:00:00 +0400

An overview of Data Science in Python

This is an overview of the basics of data science in Python. Data science involves extracting knowledge and insights from data using various techniques such as data cleaning, visualization, statistical analysis, and machine learning. Python is a popular programming language in the data science community due to its rich ecosystem of libraries and tools. Let’s go through the key components of data science in Python.

How to Share a VPC from one AWS Account to Another

Tue, 27 Jun 2023 06:00:00 +0400

To share a Virtual Private Cloud (VPC) from one AWS account to another, you can use the AWS Resource Access Manager (RAM) service. RAM allows you to securely share your AWS resources with other AWS accounts while maintaining control over the resource permissions.

Here’s a step-by-step guide on how to share a VPC from one AWS account to another:

1. Set up the necessary permissions

In the account that owns the VPC (the sharing account), ensure that you have the required permissions to share the VPC. You need to have the ram:CreateResourceShare and ec2:DescribeVpc IAM permissions.

[Solved] Set CloudWatch Logs role ARN in account settings

Mon, 26 Jun 2023 06:00:00 +0400

The error message you mentioned, “CloudWatch Logs role ARN must be set in account settings to enable logging,” typically occurs when you’re trying to enable logging for an AWS service that requires a CloudWatch Logs role, but the necessary role hasn’t been set up or configured correctly in your account settings. To resolve this issue, you can follow these steps:

Sign in to the AWS Management Console.
Open the AWS CloudTrail console at https://console.aws.amazon.com/cloudtrail/.

How to Create CloudFormation with Multiple Files

Sun, 25 Jun 2023 06:00:00 +0400

To create a CloudFormation (CFN) stack with multiple files, you can follow these general steps:

Organize your resources: Divide your resources into logical groups or services. For example, you might have separate files for networking, storage, compute, and so on.
Create YAML or JSON templates: Create individual YAML or JSON templates for each group or service. Each template will define the resources specific to that group. For example, networking.yaml, storage.yaml, and compute.yaml.

Teach me Hashicorp Vault

Sat, 24 Jun 2023 06:00:00 +0400

Introduction to Hashicorp Vault

HashiCorp Vault is a popular open-source tool designed for securely storing and managing secrets, such as API keys, passwords, certificates, and other sensitive information. It provides a centralized place to store secrets, access control mechanisms, and auditing capabilities. Vault ensures that only authorized applications and users can access the secrets they need, thus improving security in an organization.

Concepts

Here’s a high-level overview of the key concepts and components of HashiCorp Vault:

How to Generate Terraform using a Bash Shell script

Fri, 23 Jun 2023 06:00:00 +0400

To generate Terraform code using a Bash shell script, you can utilize Python within the script. Here’s an example of how you can achieve this:

1. Create a new Bash script file

Open a text editor and create a new file, for example, generate_terraform.sh.

2. Add the shebang line

Start the script with the shebang line to specify that it should be interpreted using Bash:

#!/bin/bash

3. Install Required Libraries

Since you’ll be using Python within the script, ensure that Python and pip are installed on your system. You also need to install the hclwriter library. To do this, you can include the installation commands within the script:

How to Generate Terraform using Python

Thu, 22 Jun 2023 06:00:00 +0400

To generate Terraform code using Python, you can utilize the power of the language and various libraries to dynamically create and manipulate the Terraform configuration files. Here’s a step-by-step guide on how to get started:

1. Install Required Libraries

Make sure you have Python installed on your system. Additionally, install the hclwriter library, which simplifies the process of generating HCL (HashiCorp Configuration Language) code, the language used by Terraform. You can install it using pip:

Make EKS cluster private with NodeGroup access

Wed, 21 Jun 2023 06:00:00 +0400

The Theory

To make an Amazon Elastic Kubernetes Service (EKS) cluster private and allow nodes to join through a node group, you need to follow a few steps. By default, EKS creates a public cluster, but you can configure it to make it private for enhanced security. Here’s an overview of the process:

Create a VPC: Start by creating a Virtual Private Cloud (VPC) in your AWS account if you haven’t already. This VPC will be used to host your private EKS cluster.
Create private subnets: Within the VPC, create one or more private subnets. These subnets will provide the network isolation required for a private cluster. Make sure the subnets have no direct internet access and that their route tables do not have an internet gateway attached.
Create security groups: Create security groups to define the inbound and outbound traffic rules for your EKS cluster and nodes. These security groups should allow communication between the control plane and the worker nodes, as well as any other necessary network traffic.
Create a NAT gateway: Since the private subnets don’t have direct internet access, you need to set up a Network Address Translation (NAT) gateway in a public subnet to enable outbound internet connectivity for resources in the private subnets.
Configure VPC endpoints: Create VPC endpoints for EKS and EC2 to allow private communication between your EKS cluster control plane and the worker nodes. These endpoints will ensure that the control plane and nodes can communicate without requiring access to the public internet.
Create a private EKS cluster: Now, create a private EKS cluster using the AWS Management Console, AWS CLI, or AWS SDKs. During the cluster creation, specify the private subnets, security groups, and VPC endpoints you created earlier. This will ensure that the cluster is deployed within the private subnets and can communicate with the nodes via the VPC endpoints.
Create a node group: Once the cluster is created, you can proceed to create a node group. When creating the node group, specify the private subnets and security groups that you set up earlier. The node group will be deployed in the private subnets and join the private EKS cluster.

Following these steps will result in a private EKS cluster where the control plane and worker nodes communicate privately through the VPC endpoints. The private nature of the cluster enhances security by reducing exposure to the public internet.

Which is the best language to use in DevOps

Tue, 20 Jun 2023 06:00:00 +0400

In DevOps, there isn’t a single “best” language that universally applies to all situations. The choice of programming language depends on various factors, including the specific requirements of your project, existing infrastructure, team’s expertise, and the ecosystem surrounding the tools and technologies you plan to use. However, here are some commonly used languages in different areas of DevOps:

Automation and Configuration Management

Ansible: Ansible uses a declarative YAML syntax for defining configurations and automation tasks. It is known for its simplicity and ease of use.
Python: Python is a versatile language widely used in DevOps. It has a rich ecosystem of libraries and frameworks, making it suitable for automation, scripting, and building infrastructure tools.
Ruby: Ruby is the language used by Chef, another popular configuration management tool. If you plan to use Chef, having knowledge of Ruby can be beneficial.

Infrastructure as Code

Terraform: Terraform, a tool for provisioning and managing infrastructure, uses its own domain-specific language (DSL). Although it has its own DSL, it is worth noting that Terraform configurations can be written using JSON or HCL (HashiCorp Configuration Language), which is similar to JSON.
Cloud-specific languages: Cloud providers often provide their own specific languages or SDKs for infrastructure provisioning and management. For example, AWS provides AWS CloudFormation (JSON/YAML-based) and AWS SDKs for various languages such as Python, Java, and JavaScript.

Continuous Integration/Continuous Deployment (CI/CD)

Jenkinsfile (Groovy): Jenkins, a popular CI/CD tool, uses a Groovy-based DSL for defining pipelines and workflows.
YAML: Many CI/CD tools, including GitLab CI/CD and GitHub Actions, use YAML-based configuration files for defining CI/CD pipelines.

Monitoring and Data Analysis

Python: Python is often used for scripting and building monitoring tools. It has libraries like Pandas, NumPy, and matplotlib that are useful for data analysis and visualization.
Go: Go (Golang) is gaining popularity for building high-performance and scalable monitoring systems and data processing pipelines.

Moreover

In the world of DevOps, the choice of programming language plays a crucial role in effectively managing and automating various tasks. However, it’s worth noting that many DevOps tasks involve using multiple languages and tools together, rather than relying on a single language. This approach allows DevOps teams to leverage the strengths and capabilities of different languages and tools to meet their specific requirements.

How is Ansible different from Chef or Puppet

Mon, 19 Jun 2023 06:00:00 +0400

Ansible, Chef, and Puppet are all popular configuration management and automation tools, but they differ in their approach and architecture. Here’s a comparison of Ansible with Chef and Puppet:

Architecture

Ansible: Ansible follows a simple agentless architecture. It uses SSH or WinRM to connect to managed nodes and executes tasks remotely without the need for installing any agent software on the nodes.
Chef: Chef uses a client-server architecture. It requires a Chef client agent to be installed on each managed node, which communicates with a central Chef server.
Puppet: Puppet also follows a client-server architecture. It requires the installation of the Puppet agent on each managed node, which communicates with a central Puppet master.

Configuration Language

Ansible: Ansible uses YAML, a human-readable language, for defining playbooks and configurations. YAML has a simpler syntax and is easy to understand and write.
Chef: Chef uses a Ruby-based DSL (Domain-Specific Language) called the Chef DSL. It allows for more flexibility and extensibility but has a steeper learning curve for users not familiar with Ruby.
Puppet: Puppet uses its own declarative language called Puppet DSL or Puppet language. It is designed to be readable and expressive, although some users find it more complex than Ansible’s YAML.

Agent-based vs. Agentless

Ansible: Ansible is agentless, meaning it does not require a separate agent to be installed on the managed nodes. This simplifies the setup and maintenance process.
Chef: Chef and Puppet both require agents to be installed on the managed nodes, which adds an extra step and potential overhead.
Puppet: Puppet also requires agent installation on managed nodes.

Ease of Use

Ansible: Ansible is known for its simplicity and ease of use. Its YAML syntax and agentless architecture make it accessible to users with varying levels of experience.
Chef: Chef offers a higher level of flexibility but may have a steeper learning curve, especially for users who are not familiar with Ruby or DSLs.
Puppet: Puppet has a reputation for being powerful but also having a steeper learning curve due to its language and architecture.

Community and Ecosystem

Ansible: Ansible has a large and active community with extensive documentation and a wide range of community-contributed modules and playbooks available for various use cases.
Chef: Chef also has an active community and offers a rich ecosystem of cookbooks (equivalent to Ansible’s roles) available in the Chef Supermarket.
Puppet: Puppet has a well-established community and ecosystem, with a central repository called Puppet Forge that provides a collection of modules.

Making the correct choice

Overall, the choice between Ansible, Chef, or Puppet depends on your specific requirements, familiarity with different languages, preferences, and the existing infrastructure in your environment. Each tool has its strengths and can be effective for automating configuration management tasks, but Ansible’s simplicity and agentless architecture make it a popular choice for many users.

Teach me the basics of Ansible

Sun, 18 Jun 2023 06:00:00 +0400

Ansible is an open-source automation tool that allows you to manage and configure computer systems. It uses a declarative language called YAML (Yet Another Markup Language) for defining configurations and tasks. Ansible follows a client-server architecture, where the controlling machine (the Ansible server) manages and communicates with the target machines (managed nodes) over SSH.

The basics of Ansible

Inventory

An inventory file in Ansible contains a list of target hosts (managed nodes) on which Ansible performs operations. You can define the inventory in a simple text file or in dynamic inventory scripts. Each host entry can have associated variables like IP address, username, and SSH key.

How do you create an EKS cluster using CloudFormation

Sat, 17 Jun 2023 06:00:00 +0400

The steps to achieve this

To create an Amazon Elastic Kubernetes Service (EKS) cluster using CloudFormation, you can follow these steps:

Create a CloudFormation template: Start by creating a CloudFormation template in YAML or JSON format. This template will define the resources required for your EKS cluster, including the cluster itself, worker nodes, and other necessary components.
Define the EKS cluster resource: Within your CloudFormation template, define an AWS::EKS::Cluster resource. Specify the desired configuration for your EKS cluster, such as the version, name, and role-based access control (RBAC) configuration.

How to connect an API Gateway to Inline Lambda in Terraform

Fri, 16 Jun 2023 06:00:00 +0400

To connect an API Gateway to an inline Lambda function using Terraform, you can follow these steps:

Define your API Gateway and Lambda function resources in your Terraform configuration. Here’s an example:

resource "aws_api_gateway_rest_api" "my_api_gateway" {
  name = "MyApiGateway"
}

resource "aws_api_gateway_resource" "my_api_gateway_resource" {
  rest_api_id = aws_api_gateway_rest_api.my_api_gateway.id
  parent_id   = aws_api_gateway_rest_api.my_api_gateway.root_resource_id
  path_part   = "myresource"
}

resource "aws_api_gateway_method" "my_api_gateway_method" {
  rest_api_id   = aws_api_gateway_rest_api.my_api_gateway.id
  resource_id   = aws_api_gateway_resource.my_api_gateway_resource.id
  http_method   = "GET"
  authorization = "NONE"

  integration {
    type             = "AWS_PROXY"
    http_method      = "POST"
    uri              = "arn:aws:apigateway:${var.region}:lambda:path/2015-03-31/functions/${aws_lambda_function.my_lambda_function.arn}/invocations"
  }
}

resource "aws_api_gateway_deployment" "my_api_gateway_deployment" {
  rest_api_id = aws_api_gateway_rest_api.my_api_gateway.id
  stage_name  = "prod"
}

resource "aws_lambda_function" "my_lambda_function" {
  function_name = "MyLambdaFunction"
  runtime       = "python3.8"
  handler       = "index.lambda_handler"
  inline_code   = <<EOF
    def lambda_handler(event, context):
        return {
            'statusCode': 200,
            'body': 'Hello from Lambda!'
        }
  EOF
}

resource "aws_lambda_permission" "my_lambda_permission" {
  statement_id  = "AllowAPIGatewayInvoke"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.my_lambda_function.arn
  principal     = "apigateway.amazonaws.com"
  source_arn    = "arn:aws:execute-api:${var.region}:${data.aws_caller_identity.current.account_id}:${aws_api_gateway

In the above example, the Lambda function is defined inline using the inline_code property. The code inside the lambda_handler function can be customized according to your requirements.

gRPC Microservices with Go

Fri, 16 Jun 2023 00:00:00 +0000

Build high-performance microservices using gRPC and Go with advanced patterns for service communication.

Advanced gRPC Service Design

Before diving into optimization techniques, it’s essential to establish a solid foundation with well-designed gRPC services that follow best practices and leverage the full power of Protocol Buffers.

Domain-Driven Service Boundaries

When designing gRPC services, aligning service boundaries with domain contexts helps create cohesive, maintainable APIs:

// user_service.proto
syntax = "proto3";
package user;
option go_package = "github.com/example/user";

import "google/protobuf/timestamp.proto";

service UserService {
  // User lifecycle operations
  rpc CreateUser(CreateUserRequest) returns (User);
  rpc GetUser(GetUserRequest) returns (User);
  rpc UpdateUser(UpdateUserRequest) returns (User);
  rpc DeleteUser(DeleteUserRequest) returns (DeleteUserResponse);
  
  // Domain-specific operations
  rpc VerifyUserEmail(VerifyUserEmailRequest) returns (VerifyUserEmailResponse);
  rpc ResetPassword(ResetPasswordRequest) returns (ResetPasswordResponse);
  
  // Batch operations for efficiency
  rpc GetUsers(GetUsersRequest) returns (GetUsersResponse);
}

message User {
  string id = 1;
  string email = 2;
  string display_name = 3;
  bool email_verified = 4;
  google.protobuf.Timestamp created_at = 5;
  google.protobuf.Timestamp updated_at = 6;
}

// Other message definitions...

Versioning Strategies

Proper versioning is crucial for maintaining backward compatibility while evolving your APIs:

API Gateway to Inline Lambda in CloudFormation

Thu, 15 Jun 2023 06:00:00 +0400

To connect an API Gateway to an inline Lambda function using CloudFormation, you can follow these steps:

Define your API Gateway and Lambda function resources in your CloudFormation template. Here’s an example:

Resources:
  MyApiGateway:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApiGateway

  MyApiGatewayResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      RestApiId: !Ref MyApiGateway
      ParentId: !GetAtt MyApiGateway.RootResourceId
      PathPart: myresource

  MyApiGatewayMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      RestApiId: !Ref MyApiGateway
      ResourceId: !Ref MyApiGatewayResource
      HttpMethod: GET
      AuthorizationType: NONE
      Integration:
        Type: AWS_PROXY
        IntegrationHttpMethod: POST
        Uri: !Sub "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:MyLambdaFunction/invocations"

  MyApiGatewayDeployment:
    Type: AWS::ApiGateway::Deployment
    Properties:
      RestApiId: !Ref MyApiGateway

  MyApiGatewayStage:
    Type: AWS::ApiGateway::Stage
    Properties:
      StageName: prod
      RestApiId: !Ref MyApiGateway
      DeploymentId: !Ref MyApiGatewayDeployment

  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.8
      Handler: index.lambda_handler
      Code:
        ZipFile: |
          def lambda_handler(event, context):
              return {
                  'statusCode': 200,
                  'body': 'Hello from Lambda!'
              }

In the above example, the Lambda function is defined inline using the ZipFile property. The code inside the lambda_handler function can be customized according to your requirements.

How to connect an API Gateway to Lambda in CloudFormation

Wed, 14 Jun 2023 06:00:00 +0400

To connect an API Gateway to a Lambda function using CloudFormation, you can follow these steps:

Define your API Gateway and Lambda function resources in your CloudFormation template. Here’s an example:

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.8
      Handler: index.handler
      Code:
        S3Bucket: my-lambda-code-bucket
        S3Key: lambda-code.zip

  MyApiGateway:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApiGateway

Create a resource of type AWS::ApiGateway::Resource to define the resource path for your API Gateway:

  MyApiGatewayResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      RestApiId: !Ref MyApiGateway
      ParentId: !GetAtt MyApiGateway.RootResourceId
      PathPart: myresource

Create a method on the resource to define the HTTP method (e.g., GET, POST) and integration details:

  MyApiGatewayMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      RestApiId: !Ref MyApiGateway
      ResourceId: !Ref MyApiGatewayResource
      HttpMethod: GET
      AuthorizationType: NONE
      Integration:
        Type: AWS
        IntegrationHttpMethod: POST
        Uri: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyLambdaFunction.Arn}/invocations

In the above example, the Uri property references the ARN of the Lambda function.

Create DynamoDB Table & Add Items using Python 3 from Lambda

Tue, 13 Jun 2023 06:00:00 +0400

To create a DynamoDB table and add items to it using Python 3 from AWS Lambda, you can use the AWS SDK for Python, also known as Boto3. Here’s a step-by-step guide:

Set up your AWS environment:
- Install Boto3 by running pip install boto3 in your local development environment.
- Set up your AWS credentials and configure your AWS CLI or environment variables. You can find detailed instructions in the AWS documentation.
Create a Lambda function in the AWS Management Console:
- Go to the AWS Management Console and navigate to the Lambda service.
- Click on “Create function” and follow the instructions to create a new Lambda function.
- Choose the desired runtime as Python 3.x.
Write the Python code to create the DynamoDB table and add items:
- In the Lambda function code editor, enter the following code:

import boto3

def lambda_handler(event, context):
    # Create a DynamoDB client
    dynamodb = boto3.client('dynamodb')

    # Define the table name and schema
    table_name = 'YourTableName'
    table_schema = [
        {
            'AttributeName': 'ID',
            'AttributeType': 'N'
        },
        {
            'AttributeName': 'Name',
            'AttributeType': 'S'
        }
    ]

    # Create the DynamoDB table
    dynamodb.create_table(
        TableName=table_name,
        KeySchema=[
            {
                'AttributeName': 'ID',
                'KeyType': 'HASH'
            }
        ],
        AttributeDefinitions=table_schema,
        ProvisionedThroughput={
            'ReadCapacityUnits': 5,
            'WriteCapacityUnits': 5
        }
    )

    # Wait for the table to be created
    dynamodb.get_waiter('table_exists').wait(TableName=table_name)

    # Add items to the table
    items = [
        {
            'ID': {'N': '1'},
            'Name': {'S': 'Item 1'}
        },
        {
            'ID': {'N': '2'},
            'Name': {'S': 'Item 2'}
        }
    ]

    with dynamodb.batch_writer(TableName=table_name) as batch:
        for item in items:
            batch.put_item(Item=item)

    return {
        'statusCode': 200,
        'body': 'DynamoDB table created and items added successfully.'
    }

Configure the Lambda function:
- In the AWS Lambda function configuration, specify the following:
  - Handler: Enter the name of the Python file and the lambda_handler function. For example, filename.lambda_handler.
  - Runtime: Python 3.x.
  - Timeout: Set an appropriate timeout based on the expected execution time of your code.
  - Role: Choose or create an execution role with appropriate DynamoDB permissions.
Save and test the Lambda function:
- Save the Lambda function by clicking on the “Save” button.
- Test the function by clicking on the “Test” button and configuring a test event.
- Monitor the execution logs and check for any errors or exceptions.

When you invoke the Lambda function, it will create a DynamoDB table with the specified schema and add the items to it using a batch write operation. Make sure to replace 'YourTableName' with the desired name for your DynamoDB table.

How to create a Site-to-Site VPN in Boto3 Python

Mon, 12 Jun 2023 06:00:00 +0400

To create a site-to-site VPN using the Boto3 library in Python, you can utilize the boto3.client('ec2') client to interact with the AWS EC2 service. Here’s an example code snippet to create a site-to-site VPN:

import boto3

ec2_client = boto3.client('ec2')

# Create VPN Gateway
vpn_gateway_response = ec2_client.create_vpn_gateway(Type='ipsec.1', TagSpecifications=[{
    'ResourceType': 'vpn-gateway',
    'Tags': [{'Key': 'Name', 'Value': 'SiteToSiteVPN'}]
}])
vpn_gateway_id = vpn_gateway_response['VpnGateway']['VpnGatewayId']

# Create VPN Connection
vpn_connection_response = ec2_client.create_vpn_connection(
    Type='ipsec.1',
    CustomerGatewayId='<CUSTOMER_GATEWAY_ID>',
    VpnGatewayId=vpn_gateway_id,
    Options={
        'StaticRoutesOnly': True
    },
    TagSpecifications=[{
        'ResourceType': 'vpn-connection',
        'Tags': [{'Key': 'Name', 'Value': 'SiteToSiteVPNConnection'}]
    }]
)
vpn_connection_id = vpn_connection_response['VpnConnection']['VpnConnectionId']

# Create VPN Connection Route
ec2_client.create_vpn_connection_route(
    DestinationCidrBlock='<DESTINATION_CIDR_BLOCK>',
    VpnConnectionId=vpn_connection_id
)

In the above code, you need to replace <CUSTOMER_GATEWAY_ID> with the ID of the customer gateway representing the remote site, and <DESTINATION_CIDR_BLOCK> with the CIDR block of the remote network you want to connect to.

How to create a Site-to-Site VPN in Terraform

Sun, 11 Jun 2023 06:00:00 +0400

To create a site-to-site VPN using Terraform, you can use the aws_vpn_gateway and aws_vpn_connection resources from the AWS provider. Here’s an example Terraform configuration to create a site-to-site VPN:

resource "aws_vpn_gateway" "vpn_gateway" {
  vpc_id       = "<VPC_ID>"
  tags = {
    Name = "SiteToSiteVPN"
  }
}

resource "aws_vpn_connection" "vpn_connection" {
  customer_gateway_id = "<CUSTOMER_GATEWAY_ID>"
  vpn_gateway_id     = aws_vpn_gateway.vpn_gateway.id
  type               = "ipsec.1"
  static_routes_only = true

  tags = {
    Name = "SiteToSiteVPNConnection"
  }
}

resource "aws_vpn_connection_route" "vpn_connection_route" {
  destination_cidr_block = "<DESTINATION_CIDR_BLOCK>"
  vpn_connection_id     = aws_vpn_connection.vpn_connection.id
}

In the above Terraform configuration, you need to replace <VPC_ID> with the ID of the VPC where the VPN gateway will be attached, <CUSTOMER_GATEWAY_ID> with the ID of the customer gateway representing the remote site, and <DESTINATION_CIDR_BLOCK> with the CIDR block of the remote network you want to connect to.

How to create a Site-to-Site VPN in CloudFormation

Sat, 10 Jun 2023 06:00:00 +0400

To create a site-to-site VPN (Virtual Private Network) using AWS CloudFormation, you can use the AWS::EC2::VPNGateway and AWS::EC2::VPNConnection resources. Here’s an example CloudFormation template to create a site-to-site VPN:

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  VpnGateway:
    Type: AWS::EC2::VPNGateway
    Properties:
      Type: ipsec.1
      Tags:
        - Key: Name
          Value: SiteToSiteVPN

  VpnConnection:
    Type: AWS::EC2::VPNConnection
    Properties:
      Type: ipsec.1
      CustomerGatewayId: <CUSTOMER_GATEWAY_ID>
      VpnGatewayId: !Ref VpnGateway
      StaticRoutesOnly: true
      Tags:
        - Key: Name
          Value: SiteToSiteVPNConnection

  VpnConnectionRoute:
    Type: AWS::EC2::VPNConnectionRoute
    Properties:
      DestinationCidrBlock: <DESTINATION_CIDR_BLOCK>
      VpnConnectionId: !Ref VpnConnection

In the above template, you need to replace <CUSTOMER_GATEWAY_ID> with the ID of the customer gateway representing the remote site, and <DESTINATION_CIDR_BLOCK> with the CIDR block of the remote network you want to connect to.

How to AWS sts assume role in one command - without jq

Fri, 09 Jun 2023 06:00:00 +0400

The issue - what it takes to assume a role

To assume an AWS role in the CLI, you will have to do something like this:

aws sts assume-role --role-arn arn:aws:iam::123456789123:role/myAwesomeRole --role-session-name test --region eu-central-1

This will give you the following output:

{
    "Credentials": {
        "AccessKeyId": "someAccessKeyId",
        "SecretAccessKey": "someSecretAccessKey",
        "SessionToken": "someSessionToken",
        "Expiration": "20203-01-02T06:52:13+00:00"
    },
    "AssumedRoleUser": {
        "AssumedRoleId": "idOfTheAssummedRole",
        "Arn": "theARNOfTheRoleIWantToAssume"
    }
}

But then you will have to manually copy and paste the values of AccessKeyId, SecretAccessKey and SessionToken in a bunch of exports like this:

How to create a Lambda in CloudFormation

Wed, 07 Jun 2023 06:00:00 +0400

You can create a Lambda in CloudFormation as follows:

Option 1 - Inline code

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.8
      Handler: index.lambda_handler
      Code:
        ZipFile: |
          import json

          def lambda_handler(event, context):
              # Your Lambda function code here
              return {
                  'statusCode': 200,
                  'body': json.dumps('Hello from Lambda!')
              }
      Role: !GetAtt MyLambdaExecutionRole.Arn

In this example, instead of specifying the S3Bucket and S3Key properties under the Code section, you use the ZipFile property to provide the actual code as a multiline string. The code is written in Python and includes a simple Lambda handler function.

How to create a Lambda in Terraform

Wed, 07 Jun 2023 06:00:00 +0400

To create an AWS Lambda function using Terraform, you need to define the necessary resources in a Terraform configuration file. Here’s an example of how you can create a Lambda function using Terraform:

Option 1 - Seperate Lambda Source

Create a new directory for your Terraform configuration and navigate to it in your terminal.
Create a new file with a .tf extension, such as lambda.tf, and open it in a text editor.
In the lambda.tf file, add the following code:

provider "aws" {
  region = "us-east-1"  # Replace with your desired AWS region
}

resource "aws_lambda_function" "my_lambda" {
  function_name = "my-lambda-function"
  role          = aws_iam_role.lambda_role.arn
  handler       = "index.handler"
  runtime       = "nodejs14.x"  # Replace with your desired runtime

  // Replace with the path to your Lambda function code
  filename      = "path/to/lambda/code.zip"

  // Replace with the appropriate values for your Lambda function
  environment {
    variables = {
      KEY   = "VALUE"
      KEY2  = "VALUE2"
    }
  }
}

resource "aws_iam_role" "lambda_role" {
  name = "my-lambda-role"
  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}
EOF
}

resource "aws_iam_role_policy_attachment" "lambda_policy_attachment" {
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
}

In the above code, you can customize the following parts:

region: Specify the AWS region where you want to create the Lambda function.
runtime: Specify the runtime environment for your Lambda function (e.g., nodejs14.x, python3.8, etc.).
filename: Update the path to your Lambda function code. Ensure that the code is packaged in a ZIP file.

You can also modify the environment variables section (KEY and VALUE) according to your requirements.

How to create a Bastion server in Terraform

Tue, 06 Jun 2023 06:00:00 +0400

To create a Bastion server using Terraform, you need to define the necessary resources in a Terraform configuration file. Here’s an example of how you can create a Bastion server using Terraform:

# Define the security group
resource "aws_security_group" "bastion_sg" {
  name        = "bastion-security-group"
  description = "Bastion Security Group"
  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }
  vpc_id = "your-vpc-id"
}

# Define the Bastion instance
resource "aws_instance" "bastion_instance" {
  ami           = "your-ami-id"
  instance_type = "t2.micro"  # Update with the desired instance type
  key_name      = "your-key-pair-name"
  security_group_ids = [aws_security_group.bastion_sg.id]
  user_data     = <<-EOF
    #!/bin/bash
    echo "AllowTcpForwarding yes" >> /etc/ssh/sshd_config
    service sshd restart
    iptables -t nat -A PREROUTING -p tcp --dport 22 -j REDIRECT --to-port 2222
    iptables-save > /etc/sysconfig/iptables
    systemctl enable iptables
    systemctl restart iptables
    EOF
}

# Allocate an Elastic IP and associate it with the Bastion instance
resource "aws_eip" "bastion_eip" {
  instance = aws_instance.bastion_instance.id
}

In the Terraform configuration:

How to create a Bastion server in CloudFormation

Mon, 05 Jun 2023 06:00:00 +0400

To create a Bastion server using AWS CloudFormation, you need to define the necessary resources in a CloudFormation template. Here’s an example of how you can create a Bastion server using CloudFormation:

AWSTemplateFormatVersion: "2010-09-09"
Resources:
  BastionSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Bastion Security Group
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: 0.0.0.0/0
      VpcId: "your-vpc-id"
  BastionInstance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: "your-ami-id"
      InstanceType: "t2.micro"  # Update with the desired instance type
      SecurityGroupIds:
        - !Ref BastionSecurityGroup
      KeyName: "your-key-pair-name"
      UserData:
        Fn::Base64: !Sub |
          #!/bin/bash
          echo "AllowTcpForwarding yes" >> /etc/ssh/sshd_config
          service sshd restart
          iptables -t nat -A PREROUTING -p tcp --dport 22 -j REDIRECT --to-port 2222
          iptables-save > /etc/sysconfig/iptables
          systemctl enable iptables
          systemctl restart iptables
  BastionEIP:
    Type: AWS::EC2::EIP
    Properties:
      InstanceId: !Ref BastionInstance

In the CloudFormation template:

How to you create a Cross Account Role in Terraform

Sun, 04 Jun 2023 06:00:00 +0400

To create a cross-account role in Terraform, you need to perform the following steps:

1. Define the IAM role

Define the IAM role in the Terraform configuration

resource "aws_iam_role" "cross_account_role" {
  name               = "CrossAccountRole"
  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::<ACCOUNT_ID>:root"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}
EOF
}

In the assume_role_policy section, replace <ACCOUNT_ID> with the AWS account ID of the target account that will assume this role.

How to you create a Cross Account Role in CloudFormation

Sat, 03 Jun 2023 06:00:00 +0400

To create a cross-account role in CloudFormation, you can follow these steps:

1. Create a CloudFormation template

Create a new CloudFormation template in YAML or JSON format. This template will define the resources, including the cross-account role, that you want to create.

2. Define the cross-account role

Within your CloudFormation template, define the cross-account role using the AWS::IAM::Role resource type. Specify the necessary properties such as RoleName, AssumeRolePolicyDocument, and ManagedPolicyArns.

How to create Public and Private Subnets in CloudFormation

Fri, 02 Jun 2023 06:00:00 +0400

To create public and private subnets in AWS CloudFormation, you can use the AWS CloudFormation Template Language (CFT) to define your network configuration. Here’s an example CloudFormation template that demonstrates how to create public and private subnets within a Virtual Private Cloud (VPC) in AWS:

Resources:
  MyVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      Tags:
        - Key: Name
          Value: my-vpc

  PublicSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: 10.0.0.0/24
      AvailabilityZone: us-west-2a
      Tags:
        - Key: Name
          Value: public-subnet

  PrivateSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: us-west-2b
      Tags:
        - Key: Name
          Value: private-subnet

In this example, the AWS::EC2::VPC resource creates a VPC with the specified CIDR block. The AWS::EC2::Subnet resources create the public and private subnets within the VPC, using different CIDR blocks and availability zones.

How to create Public and Private Subnets in Terraform

Thu, 01 Jun 2023 06:00:00 +0400

To create public and private subnets in Terraform, you can use the AWS provider to define your network configuration. Here’s an example configuration that demonstrates how to create public and private subnets within a Virtual Private Cloud (VPC) in AWS:

# Define your AWS provider configuration
provider "aws" {
  region = "us-west-2"  # Update with your desired region
}

# Create the VPC
resource "aws_vpc" "my_vpc" {
  cidr_block = "10.0.0.0/16"  # Update with your desired VPC CIDR block

  tags = {
    Name = "my-vpc"
  }
}

# Create the public subnet
resource "aws_subnet" "public_subnet" {
  vpc_id            = aws_vpc.my_vpc.id
  cidr_block        = "10.0.0.0/24"  # Update with your desired public subnet CIDR block
  availability_zone = "us-west-2a"  # Update with your desired availability zone

  tags = {
    Name = "public-subnet"
  }
}

# Create the private subnet
resource "aws_subnet" "private_subnet" {
  vpc_id            = aws_vpc.my_vpc.id
  cidr_block        = "10.0.1.0/24"  # Update with your desired private subnet CIDR block
  availability_zone = "us-west-2b"  # Update with your desired availability zone

  tags = {
    Name = "private-subnet"
  }
}

In this example, the aws_vpc resource creates a VPC with the specified CIDR block. The aws_subnet resources create the public and private subnets within the VPC, using different CIDR blocks and availability zones.

Create Internet Gateway & Assign to EC2 in CloudFormation

Wed, 31 May 2023 06:00:00 +0400

To create an Internet Gateway and associate it with an EC2 instance using AWS CloudFormation, you can follow these steps:

Step 1: Create a CloudFormation template

Create a new YAML or JSON file with a .yaml or .json extension (e.g., template.yaml), and add the following contents:

AWSTemplateFormatVersion: "2010-09-09"
Resources:
  MyVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16  # Replace with your desired VPC CIDR block

  MyInternetGateway:
    Type: AWS::EC2::InternetGateway

  MyVPCGatewayAttachment:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref MyVPC
      InternetGatewayId: !Ref MyInternetGateway

  MySubnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: 10.0.0.0/24  # Replace with your desired subnet CIDR block
      AvailabilityZone: us-west-2a  # Replace with your desired availability zone

  MyRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref MyVPC

  MyDefaultRoute:
    Type: AWS::EC2::Route
    DependsOn: MyVPCGatewayAttachment
    Properties:
      RouteTableId: !Ref MyRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref MyInternetGateway

  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: ami-0123456789abcdef0  # Replace with your desired AMI ID
      InstanceType: t2.micro  # Replace with your desired instance type
      SubnetId: !Ref MySubnet

Make sure to replace the placeholder values (CidrBlock, AvailabilityZone, ImageId, etc.) with your desired values.

Create Internet Gateway & Assign to EC2 in Terraform

Tue, 30 May 2023 06:00:00 +0400

To create an Internet gateway and assign it to an EC2 instance using Terraform, you can follow these steps:

Step 1: Set up your Terraform environment

Install Terraform: Download and install Terraform from the official website (https://www.terraform.io/downloads.html) based on your operating system.
Configure AWS credentials: Set up your AWS access key and secret access key as environment variables or use an AWS profile configured on your system.

Step 2: Create a Terraform configuration file

Create a new file with a .tf extension (e.g., main.tf) and add the following contents:

How to configure Terraform to use Local Providers from Nexus

Mon, 29 May 2023 06:00:00 +0400

If your organization has blocked registry.terraform.io and has instead downloaded the provider binaries to Nexus, then you can do the following to still make your Terraform execute correctly.

Step 1 - Download the Required Providers

In our example, we need the following providers:

AWS
Archive

These commands below are running directly from the pipeline that executes the Terraform:

# Download the providers from the Nexus repository
- curl -u ${Nexus_REPO_USER}:${Nexus_REPO_PASS} -o terraform-provider-aws4.65.0linuxamd64.zip https://nexus.example.com/repository/some-local-mirror/registry.terraform.io/hashicorp/aws/terraform-provider-aws_4.65.0_linux_amd64.zip
- curl -u ${Nexus_REPO_USER}:${Nexus_REPO_PASS} -o terraform-provider-archive_2.3.0_linux_amd64.zip https://nexus.example.com/repository/local-mirror/registry.terraform.io/hashicorp/archive/terraform-provider-archive_2.3.0_linux_amd64.zip
# Make a local directory to store these providers
- mkdir -p $HOME/.terraform.d/plugins/registry.terraform.io/hashicorp/aws/
- mkdir -p $HOME/.terraform.d/plugins/registry.terraform.io/hashicorp/archive/
# Move the downloaded zip files to these directories
- mv terraform-provider-aws_4.65.0_linux_amd64.zip $HOME/.terraform.d/plugins/registry.terraform.io/hashicorp/aws/
- mv terraform-provider-archive_2.3.0_linux_amd64.zip $HOME/.terraform.d/plugins/registry.terraform.io/hashicorp/archive/
# Give the permissions (not always required)
- chmod 777 -R $HOME/.terraform.d/plugins/

Step 2 - Run the Terraform code with a Plugin Directory

The following code continues the pipeline from above where we left off:

[Solved] Fargate Can't Read Secrets from Secret Manager

Sun, 28 May 2023 06:00:00 +0400

If you’re running a Fargate task and it’s not able to read secrets from AWS Secret Manager, there are a few things you can check:

Verify that the Fargate task has the correct IAM permissions to access the secret. You need to grant the task the secretsmanager:GetSecretValue permission for the specific secret that it needs to access. You can do this by adding the necessary permission to the task execution role, or by creating a separate IAM role and attaching it to the task.

Golang vs Python: The Ultimate Battle in DevOps

Sat, 27 May 2023 06:00:00 +0400

In the world of DevOps, two programming languages are often pitted against each other: Golang and Python. Both languages have their own strengths and weaknesses, and choosing the right one for your DevOps needs can be a tough decision. In this blog post, we will take a closer look at Golang and Python, and compare their capabilities in the DevOps landscape.

Golang

Golang is a language that has gained immense popularity in recent years, especially in the field of DevOps. One of the key reasons behind its success is its simplicity, which makes it easier to learn and use. The language was designed to be fast, efficient, and reliable, with a focus on minimizing dependencies and maximizing performance. Golang’s popularity in the DevOps landscape is due to its ability to build high-performance, networked services and web applications with ease.

Why DevOps and Python are Amazing Together

Fri, 26 May 2023 06:00:00 +0400

In today’s software development world, DevOps and Python are two of the most essential elements for building high-quality software. DevOps has transformed the way software is developed, tested, and deployed, while Python has become a popular programming language for automation and scripting.

The combination of DevOps and Python is particularly powerful because it provides developers with the necessary tools to automate, test, and deploy software efficiently. Here are some of the reasons why DevOps and Python are such a great match:

Python & DevOps: Transforming Software Development

Thu, 25 May 2023 06:00:00 +0400

Introduction:

In recent years, the software industry has witnessed a remarkable shift towards DevOps and Python. DevOps has become a vital part of software development, and Python is now one of the most popular programming languages used by developers. In this blog post, we’ll explore why DevOps and Python are so amazing together, and how they can help revolutionize software development.

DevOps: A Game Changer in Software Development

DevOps is a software development methodology that aims to bridge the gap between development and operations teams. It involves collaboration, automation, and continuous delivery of software. DevOps practices have gained popularity in recent years due to their ability to improve the efficiency, quality, and speed of software development.

DevOps: The Ultimate Secret Weapon for High-Tech Success

Wed, 24 May 2023 06:00:00 +0400

DevOps has been a buzzword in the tech industry for some time now. While some companies have embraced the DevOps methodology, others are still lagging behind. If you’re wondering what all the hype is about and why DevOps is so amazing, then read on! Here are ten reasons why DevOps is the ultimate secret weapon for high-tech success.

1. Improved Collaboration and Communication

Improved collaboration and communication are critical benefits of DevOps that can have a significant impact on the success of software development projects. In traditional software development approaches, different teams often work in silos, with little communication or coordination between them. This can lead to delays, misunderstandings, and errors.

How to Deploy a Java Application in AWS ECS using Terraform

Tue, 23 May 2023 06:00:00 +0400

In order to deploy a Java application into AWS ECS (Elastic Container Service) using Terraform, we need to consider a few different things.

Step 1 - Java Application

Create a file called HelloWorld.java and add the following code to it:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

We now need to build our class as follows:

javac HelloWorld.java

Once this is done, we can package our application into a jar file:

How to set the Hostname on a Linux server with Terraform

Mon, 22 May 2023 06:00:00 +0400

If you need to set the hostname on a linux server, and you are using Terraform, then you can do the following:

Include the provisioner block and set it to remote-exec:

provisioner "remote-exec" {
  inline = ["sudo hostnamectl set-hostname friendly.example.com"]
}

Go Sync Package Mastery: Synchronization Primitives

Mon, 22 May 2023 00:00:00 +0000

Master Go’s synchronization primitives including mutexes.

#Go’s sync package contains the building blocks for safe concurrent programming. When multiple goroutines access shared data, you need synchronization to prevent race conditions and data corruption.

The sync package provides several key primitives:

Mutex: Mutual exclusion locks for protecting shared resources
RWMutex: Reader-writer locks for read-heavy workloads
WaitGroup: Waiting for a collection of goroutines to finish
Once: Ensuring a function runs exactly once
Cond: Condition variables for complex coordination
Pool: Object pools for reducing garbage collection pressure

When to Use Sync Primitives

Go’s philosophy is “Don’t communicate by sharing memory; share memory by communicating.” Channels are often the right choice for goroutine coordination. However, sync primitives are essential when:

What are the different types of AWS API Gateway Protocols?

Sun, 21 May 2023 06:00:00 +0400

Amazon API Gateway supports various protocols for exposing APIs, including:

1. RESTful API

This is the most common and widely used protocol for web APIs. Amazon API Gateway allows you to create and manage RESTful APIs, where you define API resources, methods (such as GET, POST, PUT, DELETE, etc.), and HTTP request and response mappings using API Gateway’s REST API model.

Primary use-cases include

Building traditional web APIs with standard HTTP methods (GET, POST, PUT, DELETE, etc.) and resource-based URLs.
Exposing APIs for legacy systems or third-party integrations that follow RESTful principles.
Building APIs that are consumed by a wide range of clients, such as web browsers, mobile apps, and IoT devices.

2. WebSocket API

WebSocket is a protocol that enables bidirectional communication between web clients and servers over a single, long-lived connection. With Amazon API Gateway’s WebSocket API, you can create real-time, interactive APIs that support two-way communication between clients and servers, making it suitable for use cases like chat applications, gaming, and notifications.

IaC: A Guide to Modern Software Development

Sat, 20 May 2023 06:00:00 +0400

In the world of software development, efficiency, scalability, and repeatability are paramount. Enter Infrastructure as Code (IaC), a revolutionary approach to managing infrastructure in the cloud era. In this definitive guide, we will dive deep into the concept of IaC, explore its benefits, best practices, and how it is reshaping the way modern software is built and deployed. Join us on this journey as we unlock the power of IaC and uncover its secrets to successful software development.

DevOps and Microservices: How They Complement Each Other

Fri, 19 May 2023 06:00:00 +0400

In today’s fast-paced world of software development, DevOps and microservices have emerged as two powerful methodologies that enable organizations to build and deploy applications with speed, agility, and reliability. While DevOps and microservices are distinct concepts, they often go hand in hand, complementing each other to create a seamless and efficient software development and deployment process. In this blog post, we will explore how DevOps and microservices fit together and how organizations can leverage them to accelerate their software delivery pipelines and achieve business success.

IaC Unlock: Maximize Potential with Ansible

Thu, 18 May 2023 06:00:00 +0400

In today’s fast-paced world of software development and IT operations, the need for efficient and scalable infrastructure management has become more critical than ever. Enter Infrastructure as Code (IaC), a game-changing approach that allows organizations to automate their infrastructure provisioning and management, making it more agile, scalable, and reliable. And when it comes to IaC, Ansible stands out as a top choice for many IT teams due to its simplicity, versatility, and robustness. In this blog post, we will explore the power of IaC with Ansible and how it can revolutionize your IT operations.

GitOps: Managing Infrastructure as Code with Git

Wed, 17 May 2023 06:00:00 +0400

Introduction

In today’s fast-paced world of software development and operations, managing infrastructure efficiently and securely is crucial for organizations to deliver reliable and scalable applications. Traditional methods of managing infrastructure can be time-consuming, error-prone, and lack visibility, making it challenging to keep up with the demands of modern software development practices. However, with the emergence of GitOps, organizations now have a powerful and efficient way to manage infrastructure as code, leveraging the familiar and widely adopted Git version control system. In this blog post, we will explore the concept of GitOps, its benefits, and how organizations can implement GitOps practices to streamline their infrastructure management while adhering to popular SEO tactics.

DevOps Synergy: Boosting Cybersecurity

Tue, 16 May 2023 06:00:00 +0400

As organizations increasingly rely on technology to power their operations, the need for robust cybersecurity measures becomes more critical than ever. Cyber threats are constantly evolving, and traditional security approaches are no longer sufficient to protect against sophisticated attacks. This is where DevOps, a collaborative approach to software development and operations, can play a significant role in enhancing cybersecurity defenses. In this blog post, we will explore the powerful synergy between DevOps and cybersecurity, and how organizations can leverage this approach to strengthen their security posture.

The Role of DevOps in Blockchain

Mon, 15 May 2023 06:00:00 +0400

Blockchain technology is gaining traction across various industries for its ability to provide transparency, security, and immutability. However, implementing blockchain solutions requires a robust and efficient software development process, which is where DevOps comes in. In this blog post, we will explore the role of DevOps in blockchain development and how it can help organizations deploy blockchain solutions seamlessly.

What is DevOps?

DevOps is a software development methodology that emphasizes collaboration, automation, and continuous delivery to ensure faster and more reliable software delivery. The approach combines the practices of agile software development, continuous integration, and continuous delivery/deployment. DevOps focuses on breaking down the silos between development and operations teams, enabling seamless collaboration and communication.

The Importance of Testing in DevOps: Strategies and Tools

Sun, 14 May 2023 06:00:00 +0400

Introduction

In today’s fast-paced digital world, software development has become an essential part of business operations. With the adoption of DevOps practices, organizations can build and deploy software applications more efficiently and effectively. However, with faster release cycles, it becomes increasingly important to ensure that software is thoroughly tested before release. In this blog post, we will explore the importance of testing in DevOps, strategies for successful testing, and tools that can help streamline the testing process.

Docker Production Deployment Strategies

Sun, 14 May 2023 00:00:00 +0000

Deploy Docker containers to production with security.

Introduction and Setup

My first production Docker deployment was a disaster. I thought running containers in production would be as simple as docker run with a few extra flags. Three hours into the deployment, our application was down, the database was corrupted, and I was frantically trying to figure out why containers kept restarting in an endless loop.

That painful experience taught me that production Docker deployments are fundamentally different from development. The stakes are higher, the complexity is greater, and the margin for error is essentially zero.

DevOps Impact on Customer Experience

Sat, 13 May 2023 06:00:00 +0400

DevOps has revolutionized the way organizations develop, deploy, and manage software applications. It has brought about a cultural shift that emphasizes collaboration, automation, and continuous improvement. While DevOps has many benefits for software development teams, it also has a significant impact on customer experience and business success.

In this blog post, we will explore how DevOps can improve customer experience and lead to business success.

Key Points

Faster Time-to-Market

One of the key benefits of DevOps is that it enables teams to release software faster and more frequently. This means that organizations can quickly respond to changing market demands and customer needs. By delivering new features and updates in a timely manner, organizations can improve customer satisfaction and increase their competitive edge.

Building a DevOps Culture from the Ground Up

Fri, 12 May 2023 06:00:00 +0400

DevOps has become a crucial aspect of software development, enabling teams to deliver software more efficiently and with higher quality. However, implementing DevOps is not just a matter of adopting tools and processes; it requires a cultural shift in the organization. In this blog post, we will explore the steps organizations can take to build a DevOps culture from the ground up.

1. Define the vision and goals

The first step in building a DevOps culture is to establish a clear vision and goals. This includes defining the purpose of DevOps and how it aligns with the organization’s overall strategy. This vision should be communicated clearly to all stakeholders to ensure that everyone is working towards the same goal.

Scaling DevOps for Enterprise Organizations

Thu, 11 May 2023 06:00:00 +0400

Introduction

DevOps has become a popular approach for software development in recent years, enabling teams to collaborate more effectively, increase efficiency, and deliver high-quality software faster. However, scaling DevOps for enterprise organizations can be challenging due to the size and complexity of their operations. In this blog post, we will explore the key considerations for scaling DevOps in an enterprise context and provide practical tips for success.

1. Establish a Clear Vision and Strategy

Before scaling DevOps, it’s crucial to establish a clear vision and strategy that aligns with the organization’s business objectives. This should include defining key performance indicators (KPIs) to measure success and outlining the roles and responsibilities of different teams. The strategy should also incorporate feedback loops to ensure continuous improvement and flexibility to adapt to changing business needs.

The Benefits of Infrastructure as Code in DevOps

Wed, 10 May 2023 06:00:00 +0400

Introduction

The increasing complexity of software systems requires a flexible, scalable, and reliable infrastructure. This is where infrastructure as code (IaC) comes in, providing a way to automate the management of infrastructure through code. In DevOps, IaC is a critical component that helps teams achieve continuous delivery and deployment, reduce errors, improve collaboration and communication, and ensure consistency and repeatability. In this blog post, we will explore the benefits of infrastructure as code in DevOps.

DevOps for Legacy Systems: Challenges and Solutions

Tue, 09 May 2023 06:00:00 +0400

As organizations continue to evolve and embrace digital transformation, they often encounter legacy systems that are critical to their business operations. These systems may be outdated and require modernization, but they still need to be maintained and supported in the meantime. This is where DevOps for legacy systems comes in, offering new opportunities for agility, innovation, and efficiency. In this blog post, we will explore the challenges and solutions for implementing DevOps practices for legacy systems.

DevOps Risk Management: Security & Compliance

Mon, 08 May 2023 06:00:00 +0400

DevOps has transformed software development, enabling teams to build, test, and deploy applications faster and more efficiently. However, the speed and agility of DevOps also bring new risks, particularly in the areas of security and compliance. To mitigate these risks, DevOps teams need to adopt strategies that incorporate security and compliance into the development process from the start. In this blog post, we will discuss some of the key strategies for managing risk in DevOps.

Why DevOps is Critical for Digital Transformation

Sun, 07 May 2023 06:00:00 +0400

Digital transformation is the process of adopting and implementing digital technologies to improve business operations, increase efficiency, and enhance customer experience. The adoption of digital technologies has become essential for businesses to remain competitive in today’s fast-paced environment. However, implementing digital transformation is not just about technology, it requires a significant cultural shift in the organization. One of the key elements of digital transformation is the implementation of DevOps. In this blog post, we will explore why DevOps is critical for digital transformation.

The Role of Microservices in DevOps

Sat, 06 May 2023 06:00:00 +0400

In recent years, microservices have become a popular architectural style for building software applications. Microservices are small, independent services that work together to form a larger application. Each microservice is responsible for a specific task, and they communicate with each other through well-defined APIs. This approach offers many benefits, including scalability, resilience, and flexibility. In this blog post, we’ll explore the role of microservices in DevOps and how they contribute to a successful software development process.

Docker Image Management and Optimization

Sat, 06 May 2023 00:00:00 +0000

Learn advanced Docker image creation.

Introduction and Setup

Docker images are deceptively simple. You write a Dockerfile, run docker build, and you have a container image. But there’s a big difference between images that work and images that work well in production. A poorly optimized image can turn a 30-second deployment into a 20-minute ordeal, making hotfixes impossible and frustrating your entire team.

Building efficient Docker images requires understanding layers, caching strategies, and the subtle art of Dockerfile optimization. The techniques in this guide will help you create images that are fast to build, quick to deploy, and secure by default.

Achieving Continuous Delivery with DevOps and Automation

Fri, 05 May 2023 06:00:00 +0400

Continuous delivery is a DevOps practice that aims to automate the entire software delivery process, from code commit to production deployment. With continuous delivery, teams can deliver software faster and with greater reliability. By automating many of the manual steps involved in software delivery, teams can reduce the risk of errors and increase the speed of deployment.

To achieve continuous delivery, DevOps teams must prioritize automation. Here are some best practices for achieving continuous delivery with DevOps and automation:

The Importance of Collaboration in DevOps Culture

Thu, 04 May 2023 06:00:00 +0400

Collaboration is a key aspect of DevOps culture, and it plays a crucial role in driving success and delivering value to customers. In today’s fast-paced business environment, DevOps teams need to work together seamlessly to ensure that applications are developed and deployed quickly and efficiently, while maintaining high quality and security standards. In this blog post, we will discuss the importance of collaboration in DevOps culture and how it can lead to better outcomes for organizations.

Cloud-Native: Key to DevOps Success

Wed, 03 May 2023 06:00:00 +0400

In recent years, cloud-native architecture has become a buzzword in the world of DevOps. But what exactly does it mean, and why is it so important for DevOps success? In this blog post, we’ll explore the concept of cloud-native architecture and why it’s essential for DevOps teams to embrace it.

What is Cloud-Native Architecture?

Cloud-native architecture is an approach to building and running applications that takes advantage of the scalability and flexibility of cloud computing. It’s built around the idea of containerization, which means that applications are broken down into smaller, more manageable components that can be easily deployed and scaled as needed.

10 Best Practices for Continuous Integration in DevOps

Tue, 02 May 2023 06:00:00 +0400

Continuous Integration (CI) is an essential part of modern software development and is integral to the DevOps methodology. CI ensures that every code change made by developers is integrated and tested with the existing codebase, allowing teams to catch and fix issues early in the development cycle. In this blog post, we’ll explore the best practices for implementing Continuous Integration in DevOps.

1. Automate the build process

Automating the build process in CI involves using tools and scripts to build, package, and deploy software artifacts. The process should be designed to be repeatable and reliable so that the same results can be achieved consistently. Automating the build process not only reduces the risk of human error but also increases the speed and efficiency of the development process.

DevOps vs. Agile: What's the Difference and Why it Matters

Mon, 01 May 2023 06:00:00 +0400

Introduction

In the world of software development, there are two methodologies that are often mentioned: Agile and DevOps. While they share some similarities, they are distinct and have different goals. In this blog post, we’ll explore the differences between Agile and DevOps, why they matter, and how they can work together.

What is Agile?

Agile is a software development methodology that emphasizes collaboration, flexibility, and responsiveness. It was first introduced in 2001 with the publication of the Agile Manifesto, which outlined a set of guiding principles for software development. The Agile approach values working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a plan.

The Future of DevOps: Emerging Trends and Technologies

Sun, 30 Apr 2023 06:00:00 +0400

In recent years, DevOps has emerged as a key practice for modern software development, helping organizations to achieve faster delivery of high-quality applications. However, as the technology landscape continues to evolve, DevOps itself is undergoing significant changes to keep pace with emerging trends and technologies. In this blog post, we will explore the future of DevOps and the emerging trends and technologies that are shaping its evolution.

Serverless computing

Serverless computing is an approach to cloud computing that allows developers to write and run code without having to manage the underlying infrastructure. In a serverless architecture, the cloud provider is responsible for managing the servers, storage, and networking, while the developer can focus solely on writing code to deliver business value.

Building Resilient Microservices with Istio and Envoy

Sat, 29 Apr 2023 06:00:00 +0400

As microservices architecture continues to grow in popularity, it’s becoming increasingly important to ensure that these distributed systems are reliable and resilient. Istio and Envoy are two tools that have emerged to help with this challenge. In this blog post, we’ll explore how Istio and Envoy can be used to build resilient microservices.

Introduction to Istio and Envoy

Istio is an open-source service mesh that provides a unified way to connect, manage, and secure microservices. Envoy is a high-performance proxy that can be used to manage and secure service-to-service communication. Together, these tools provide a powerful platform for building resilient microservices.

The Role of DevSecOps in Modern Software Development

Fri, 28 Apr 2023 06:00:00 +0400

As the world becomes increasingly digital, software development has become a critical aspect of business success. However, the rise in cybersecurity threats has made it imperative to ensure that software is developed securely. This is where DevSecOps comes in – it is the integration of security practices into the DevOps process, allowing for more secure and reliable software development. In this blog post, we will discuss the role of DevSecOps in modern software development.

5 Key Metrics to Measure DevOps Success

Thu, 27 Apr 2023 06:00:00 +0400

As DevOps continues to gain popularity and adoption, it is important for organizations to measure the success of their DevOps initiatives. While DevOps is about culture and collaboration, it is also about delivering value to customers quickly and reliably. In this blog post, we will discuss five key metrics that organizations can use to measure the success of their DevOps initiatives.

1. Lead Time for Changes

Lead time for changes is the amount of time it takes for a change to be implemented, from the moment it is requested to the moment it is deployed. This metric measures how quickly an organization can deliver new features or fix issues. A shorter lead time for changes means that an organization can respond to market demands more quickly, reducing time to market and increasing customer satisfaction.

The Importance of Infrastructure as Code in DevOps

Wed, 26 Apr 2023 06:00:00 +0400

Infrastructure as Code (IaC) is a methodology that involves managing and provisioning infrastructure through code rather than manually configuring hardware and software components. This approach is essential in DevOps because it enables teams to manage infrastructure at scale, improve collaboration, and reduce errors. In this blog post, we will explore the importance of IaC in DevOps and why it is critical for modern software development.

1. Consistency and Reproducibility

Manual infrastructure configuration is prone to errors and can be challenging to reproduce consistently. With IaC, teams can define infrastructure configurations in code and version control systems, ensuring that infrastructure is consistent across environments. This approach ensures that the infrastructure is reproducible, which reduces errors and saves time.

Docker Security and Performance Optimization

Wed, 26 Apr 2023 00:00:00 +0000

Implement Docker security best practices.

Introduction and Setup

Docker Security and Optimization: Introduction and Setup

Docker security and performance optimization are critical for production deployments. This guide covers comprehensive security hardening, performance tuning, and operational best practices for containerized environments.

Docker Security Fundamentals

Security Model Overview

┌─────────────────────────────────────────────────────────┐
│                 Host Operating System                   │
├─────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐     │
│  │   Kernel    │  │  Namespaces │  │   cgroups   │     │
│  │ Capabilities│  │             │  │             │     │
│  └─────────────┘  └─────────────┘  └─────────────┘     │
├─────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐     │
│  │   SELinux/  │  │  AppArmor   │  │   seccomp   │     │
│  │  AppArmor   │  │             │  │             │     │
│  └─────────────┘  └─────────────┘  └─────────────┘     │
├─────────────────────────────────────────────────────────┤
│                 Docker Engine                           │
├─────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐     │
│  │ Container 1 │  │ Container 2 │  │ Container 3 │     │
│  └─────────────┘  └─────────────┘  └─────────────┘     │
└─────────────────────────────────────────────────────────┘

Basic Security Commands

# Run container with security options
docker run --security-opt no-new-privileges:true \
  --cap-drop ALL \
  --cap-add NET_BIND_SERVICE \
  --read-only \
  --tmpfs /tmp:rw,noexec,nosuid,size=100m \
  nginx

# Run as non-root user
docker run --user 1000:1000 \
  -v /etc/passwd:/etc/passwd:ro \
  -v /etc/group:/etc/group:ro \
  alpine id

# Limit resources
docker run --memory=512m \
  --cpus="1.5" \
  --pids-limit=100 \
  --ulimit nofile=1024:1024 \
  myapp

# Network security
docker run --network none alpine
docker run --network custom-network \
  --ip 172.20.0.10 \
  myapp

Container Hardening Basics

Secure Dockerfile Practices

# Use specific versions, not latest
FROM node:16.17.0-alpine3.16

# Create non-root user early
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nextjs -u 1001 -G nodejs

# Set working directory
WORKDIR /app

# Copy package files first for better caching
COPY package*.json ./

# Install dependencies as root, then switch
RUN npm ci --only=production && \
    npm cache clean --force && \
    chown -R nextjs:nodejs /app

# Copy application files
COPY --chown=nextjs:nodejs . .

# Switch to non-root user
USER nextjs

# Remove unnecessary packages
RUN apk del --purge \
    && rm -rf /var/cache/apk/* \
    && rm -rf /tmp/*

# Set secure permissions
RUN chmod -R 755 /app && \
    chmod 644 /app/package.json

# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1

# Expose port
EXPOSE 3000

# Use exec form for CMD
CMD ["node", "server.js"]

Runtime Security Configuration

# Comprehensive security flags
docker run -d \
  --name secure-app \
  --user 1000:1000 \
  --read-only \
  --tmpfs /tmp:rw,noexec,nosuid,size=100m \
  --tmpfs /var/run:rw,noexec,nosuid,size=50m \
  --cap-drop ALL \
  --cap-add CHOWN \
  --cap-add SETGID \
  --cap-add SETUID \
  --security-opt no-new-privileges:true \
  --security-opt apparmor:docker-default \
  --security-opt seccomp:default \
  --memory=512m \
  --memory-swap=512m \
  --cpu-shares=512 \
  --pids-limit=100 \
  --ulimit nofile=1024:1024 \
  --ulimit nproc=64:64 \
  --restart=unless-stopped \
  myapp:latest

Performance Optimization Basics

Resource Management

# CPU optimization
docker run -d \
  --cpus="2.5" \
  --cpu-shares=1024 \
  --cpuset-cpus="0,1" \
  --cpu-quota=50000 \
  --cpu-period=100000 \
  myapp

# Memory optimization
docker run -d \
  --memory=2g \
  --memory-swap=2g \
  --memory-reservation=1g \
  --oom-kill-disable=false \
  --kernel-memory=500m \
  myapp

# I/O optimization
docker run -d \
  --device-read-bps /dev/sda:50mb \
  --device-write-bps /dev/sda:50mb \
  --device-read-iops /dev/sda:1000 \
  --device-write-iops /dev/sda:1000 \
  myapp

# Network optimization
docker run -d \
  --sysctl net.core.somaxconn=65535 \
  --sysctl net.ipv4.tcp_max_syn_backlog=65535 \
  --sysctl net.core.rmem_max=134217728 \
  --sysctl net.core.wmem_max=134217728 \
  myapp

Docker Daemon Optimization

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  },
  "storage-driver": "overlay2",
  "storage-opts": [
    "overlay2.override_kernel_check=true"
  ],
  "default-ulimits": {
    "nofile": {
      "Name": "nofile",
      "Hard": 64000,
      "Soft": 64000
    }
  },
  "max-concurrent-downloads": 10,
  "max-concurrent-uploads": 5,
  "default-shm-size": "128M",
  "userland-proxy": false,
  "experimental": false,
  "metrics-addr": "127.0.0.1:9323",
  "live-restore": true
}

Security Scanning and Assessment

Image Vulnerability Scanning

# Install and use Trivy
curl -sfL https://raw.githubusercontent.com/aquasecurity/trivy/main/contrib/install.sh | sh -s -- -b /usr/local/bin

# Scan image for vulnerabilities
trivy image nginx:latest

# Scan with specific severity
trivy image --severity HIGH,CRITICAL nginx:latest

# Scan and output to file
trivy image --format json --output results.json nginx:latest

# Scan filesystem
trivy fs .

# Scan with ignore file
trivy image --ignorefile .trivyignore nginx:latest

.trivyignore example:

How to Build a Successful DevOps Toolchain

Mon, 24 Apr 2023 06:00:00 +0400

DevOps toolchains are essential for streamlining software delivery and ensuring that teams can work efficiently and collaboratively. However, building a successful DevOps toolchain requires careful planning, coordination, and evaluation. In this blog post, we will explore some strategies for building a successful DevOps toolchain that can help teams deliver software faster and more reliably.

1. Define the requirements

The first step in building a successful DevOps toolchain is defining the requirements. Teams should identify the key features and capabilities they need, such as continuous integration, automated testing, deployment automation, and monitoring. They should also consider factors such as integration with existing systems, scalability, and ease of use.

Scaling DevOps: Strategies for Managing Large Teams

Mon, 24 Apr 2023 06:00:00 +0400

DevOps has revolutionized software development and delivery, enabling teams to work collaboratively, automate processes, and deliver software faster and more reliably. However, as organizations grow and teams become larger, managing DevOps at scale becomes more challenging. In this blog post, we will explore some strategies for managing large DevOps teams and ensuring successful software delivery.

1. Embrace modular architecture

Modular architecture is a critical aspect of scaling DevOps. By breaking down applications into smaller, more manageable components, teams can work independently, reducing dependencies and improving agility. This approach also enables teams to adopt different technologies and tools, allowing for experimentation and innovation.

Docker Compose: Multi-Container Orchestration

Mon, 24 Apr 2023 00:00:00 +0000

Master Docker Compose for defining.

Introduction and Setup

Docker Compose Orchestration: Introduction and Setup

Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services, networks, and volumes, then create and start all services with a single command.

What is Docker Compose?

Docker Compose solves the complexity of managing multiple containers by providing:

Declarative Configuration: Define your entire application stack in a single YAML file
Service Orchestration: Manage dependencies between containers
Environment Management: Easy switching between development, testing, and production
Scaling: Scale services up or down with simple commands
Networking: Automatic network creation and service discovery

Installation and Setup

Installing Docker Compose

Linux:

Why DevOps Culture is Critical for Business Success

Sun, 23 Apr 2023 06:00:00 +0400

The DevOps movement has been gaining momentum in recent years as organizations realize the benefits of breaking down silos between development and operations teams. DevOps is not just a set of tools and practices; it’s a culture that emphasizes collaboration, communication, and continuous improvement. In this blog post, we will explore why DevOps culture is critical for business success.

1. Speed and agility

In today’s fast-paced business environment, organizations need to deliver software quickly and adapt to changing customer demands. DevOps culture emphasizes automation, continuous delivery, and feedback loops, enabling teams to deploy software faster and respond to market changes quickly. By breaking down silos between teams and fostering a culture of collaboration and communication, DevOps enables organizations to deliver software faster while maintaining quality.

The Ultimate Guide to Kubernetes Deployment Strategies

Sat, 22 Apr 2023 06:00:00 +0400

Kubernetes has become a popular choice for container orchestration, providing developers with a powerful platform for deploying, scaling, and managing containerized applications. However, with great power comes great responsibility, and choosing the right deployment strategy is essential for ensuring application availability, scalability, and performance. In this post, we will cover the ultimate guide to Kubernetes deployment strategies, including their benefits, drawbacks, and best practices.

1. Rolling updates

Rolling updates are the most common deployment strategy in Kubernetes, allowing you to update a running application without downtime. In this strategy, Kubernetes replaces old replicas with new ones, gradually rolling out updates while keeping the application running. This approach is useful for applications that require high availability and can handle small disruptions.

10 Best Practices for Container Security in DevOps

Fri, 21 Apr 2023 06:00:00 +0400

Containers have become a critical component of modern software development practices. They provide a lightweight, portable, and scalable way to package and deploy software applications. However, containers also introduce new security challenges, such as vulnerabilities in container images, insecure configurations, and compromised host environments. In this post, we will outline 10 best practices for container security in DevOps to help you mitigate these risks.

1. Use trusted base images

When building container images, it’s essential to use trusted base images from reputable sources. Avoid using unverified images from unknown sources, as they may contain hidden vulnerabilities or malware. Instead, use base images that have been thoroughly tested and validated by the community.

How to Implement CI/CD Pipelines with Jenkins

Thu, 20 Apr 2023 06:00:00 +0400

Continuous Integration and Continuous Deployment (CI/CD) pipelines are critical components of modern software development practices. They enable development teams to deliver high-quality software quickly and reliably by automating the build, test, and deployment process. Jenkins is a popular open-source automation tool that can help you implement CI/CD pipelines easily. In this post, we will guide you through the process of setting up a basic CI/CD pipeline with Jenkins.

Step 1: Install Jenkins

The first step is to install Jenkins on your system. You can download the latest version of Jenkins from the official website and follow the installation instructions. Once you have installed Jenkins, you can access it using the default URL http://localhost:8080.

[Solved] AWS Error: TooManyBuckets - Bucket Limit Exceeded

Wed, 19 Apr 2023 06:00:00 +0400

If you get the following error:

│ Error: creating Amazon S3 (Simple Storage) Bucket (<your-bucket-name): TooManyBuckets: You have attempted to create more buckets than allowed │ status code: 400, request id: 0P1TV2VCEDKGFQNY, host id: gc9di71ONabECoBYkkzc7Lmqs0DOo2DVhV2kqCgNruNO6Okm5K3EXzosdf5MCxP8uI= │

The reason for the problem

There is a soft limit of 100 S3 buckets per AWS account.

Find out more

https://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html

The solution to the problem

Option 1 - Quick fix

Remove unused S3 buckets.

How to check if a program exists from a Bash/Shell script

Tue, 18 Apr 2023 06:00:00 +0400

You can look to use:

command -v <the_command>

There are also 2 other ways, that we will run through a little further down, but for now..

How to use the `command` if a conditional

if ! command -v <the_command> &> /dev/null
then
    echo "<the_command> could not be found"
    exit
fi

To summarize, there are 3 ways you can do this

Option 1 - Using `command`

command -v foo >/dev/null 2>&1 || { echo >&2 "foo is not installed. Aborting."; exit 1; }

Option 2 - Using `type`

type foo >/dev/null 2>&1 || { echo >&2 "foo is not installed. Aborting."; exit 1; }

Option 3 - Using `hash`

hash foo 2>/dev/null || { echo >&2 "foo is not installed. Aborting."; exit 1; }

The DevOps Culture

Mon, 17 Apr 2023 06:00:00 +0400

DevOps is a software development approach that emphasizes collaboration and communication between development and operations teams. DevOps culture refers to the values, principles, and practices that foster this collaboration and enable teams to work together effectively.

Here are some key elements of DevOps culture:

Collaboration

DevOps culture emphasizes collaboration between development, operations, and other stakeholders involved in the software development process. This collaboration ensures that all team members are working towards the same goal and have a shared understanding of the project.

Teach me Kubernetes - Part 7 - Sidecar Containers

Sun, 16 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a sidecar container is a secondary container that runs in the same Pod as the primary container. The sidecar container runs alongside the primary container and shares the same network namespace, IPC namespace, and mount namespace.

Here are some key features of sidecar containers in Kubernetes:

Sidecar containers are used to enhance the functionality of the primary container: The sidecar container runs alongside the primary container and provides additional functionality that the primary container needs to function properly. This can include tasks such as logging, monitoring, or proxying traffic to the primary container.

Teach me Kubernetes - Part 6 - Deployments

Sat, 15 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a Deployment is a higher-level abstraction that manages the deployment and scaling of a set of Pods. Deployments provide a declarative way to manage the desired state of your application, making it easy to roll out updates and scale your application over time.

Here are some key features of Deployments in Kubernetes:

Deployments manage the desired state of your application: You can specify the desired state of your application (e.g., how many replicas of a Pod should be running, what image to use, etc.) in a Deployment configuration file. The Deployment controller then ensures that the actual state of your application matches the desired state.

Teach me Kubernetes - Part 5 - Services

Fri, 14 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a Service is an abstraction that provides a stable, IP address and DNS name for a set of Pods. Services allow you to decouple the logical representation of your application from the underlying infrastructure, making it easier to manage and scale your application over time.

Here are some key features of Services in Kubernetes:

Services provide a stable IP address and DNS name: A Service is assigned a static IP address and DNS name that remains the same even if the underlying Pods are recreated or rescheduled. This allows other components of your application to reliably connect to the Service, without having to know the details of the underlying Pod IP addresses.

Teach me Kubernetes - Part 4 - Replication Controllers

Thu, 13 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a ReplicationController (also known as a “ReplicaSet” in newer versions of Kubernetes) is a controller that ensures that a specified number of replicas of a Pod are running at any given time.

The ReplicationController is responsible for monitoring the state of the Pods it manages and taking corrective action if the desired state does not match the actual state. For example, if a Pod fails or is terminated, the ReplicationController will create a new Pod to replace it.

Teach me Kubernetes - Part 3 - Pods

Wed, 12 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a Pod is the smallest and simplest unit in the cluster. A Pod represents a single instance of a running process in a container, and it encapsulates one or more container images, storage resources, and network configurations. Pods are used to run and manage containerized applications in Kubernetes, and they provide a mechanism for managing and scaling containers.

Docker Networking and Storage Solutions

Wed, 12 Apr 2023 00:00:00 +0000

Master Docker networking modes.

Introduction and Setup

Docker Networking and Storage: Introduction and Setup

Docker networking and storage are fundamental concepts for building scalable, production-ready containerized applications. This guide covers everything from basic concepts to advanced patterns for managing container connectivity and data persistence.

Docker Networking Fundamentals

Network Types Overview

Docker provides several network drivers:

┌─────────────────────────────────────────────────────────┐
│                    Docker Host                          │
├─────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐     │
│  │   Bridge    │  │    Host     │  │    None     │     │
│  │  Network    │  │  Network    │  │  Network    │     │
│  └─────────────┘  └─────────────┘  └─────────────┘     │
├─────────────────────────────────────────────────────────┤
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐     │
│  │   Overlay   │  │   Macvlan   │  │   Custom    │     │
│  │  Network    │  │  Network    │  │  Network    │     │
│  └─────────────┘  └─────────────┘  └─────────────┘     │
└─────────────────────────────────────────────────────────┘

Basic Network Commands

# List networks
docker network ls

# Inspect network
docker network inspect bridge

# Create custom network
docker network create mynetwork

# Create network with specific driver
docker network create --driver bridge mybridge

# Create network with custom subnet
docker network create --subnet=172.20.0.0/16 mysubnet

# Connect container to network
docker network connect mynetwork mycontainer

# Disconnect container from network
docker network disconnect mynetwork mycontainer

# Remove network
docker network rm mynetwork

Bridge Networks

Default bridge network:

Teach me Kubernetes - Part 2 - Nodes

Tue, 11 Apr 2023 06:00:00 +0400

Looking for the entire 7 part guide? Start at the Overview

In Kubernetes, a Node is a worker machine that runs containerized applications. Nodes are responsible for running Pods, which are the smallest deployable units in Kubernetes.

Nodes in a Kubernetes cluster can be physical or virtual machines, and they typically have multiple CPUs and large amounts of memory and storage. Each Node runs a container runtime, such as Docker or containerd, which is responsible for managing the containers that run on the Node.

Teach me Kubernetes - Part 1 - Overview

Mon, 10 Apr 2023 06:00:00 +0400

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. With Kubernetes, you can manage containerized applications across multiple hosts, scale them up or down as needed, and even roll out updates without downtime.

Here are some key concepts you need to understand to get started with Kubernetes:

Nodes: A node is a physical or virtual machine that runs your containerized applications. It can be a virtual machine running in a cloud provider or a physical server in your data center.
Pods: A pod is the smallest deployable unit in Kubernetes. It’s a logical host for one or more containers, and it runs on a node. A pod can contain one or more containers that share the same network namespace, and can communicate with each other using local IP addresses.
Replication Controllers: A replication controller ensures that a specified number of replicas of a pod are running at all times. If a pod goes down, the replication controller creates a new one to replace it.
Services: A service is an abstraction layer that provides a stable IP address and DNS name for a set of pods. It acts as a load balancer, routing traffic to the appropriate pod based on a set of rules.
Deployments: A deployment manages the rollout and updates of a set of pods. It’s a higher-level concept that allows you to declaratively manage the desired state of your application.

To get started with Kubernetes, you’ll need to install a Kubernetes cluster on your local machine or on a cloud provider. You can then use the Kubernetes command-line interface (kubectl) to create and manage resources in your cluster.

How to Create a Simple Chatbot in Python

Sun, 09 Apr 2023 06:00:00 +0400

This is a simple chatbot in Python using the NLTK library.

See the below example Python code:

# Import necessary libraries
from nltk.chat.util import Chat, reflections

# Define your chatbot's responses
responses = {
    "hello": "Hello, how can I assist you?",
    "hi": "Hi there! How can I help you today?",
    "how are you": "I'm doing well, thank you for asking.",
    "what can you do": "I can help you with tasks such as finding information, setting reminders, and more!",
    "bye": "Goodbye, have a nice day!",
}

# Create a Chat instance with your responses
chatbot = Chat(responses, reflections)

# Start chatting!
chatbot.converse()

In this example, we’ve defined a dictionary of responses for our chatbot to use. The keys of the dictionary are the inputs that the user might enter, and the values are the chatbot’s responses. We then create a Chat instance with these responses and the reflections dictionary, which helps the chatbot handle variations of user input (such as changing “you are” to “I am” in responses).

Create Transit Gateway with Attachments in Terraform

Sat, 08 Apr 2023 06:00:00 +0400

The following example Terraform code snippet creates a Transit Gateway with VPC and VPN attachments:

provider "aws" {
  region = "us-west-2"
}

# Create a transit gateway
resource "aws_ec2_transit_gateway" "example" {
  description = "Example transit gateway"
}

# Create a VPC attachment
resource "aws_ec2_transit_gateway_vpc_attachment" "example_vpc_attachment" {
  subnet_ids         = ["subnet-abc123", "subnet-def456"]  # IDs of the subnets in the VPC to attach
  transit_gateway_id = aws_ec2_transit_gateway.example.id
  vpc_id             = "vpc-xyz789"  # ID of the VPC to attach
}

# Create a VPN attachment
resource "aws_ec2_transit_gateway_vpn_attachment" "example_vpn_attachment" {
  transit_gateway_id = aws_ec2_transit_gateway.example.id
  vpn_connection_id  = "vpn-123456"  # ID of the VPN connection to attach
}

In this example, we’re using the aws_ec2_transit_gateway resource type to create a transit gateway in the us-west-2 region. We’re specifying a description parameter to provide a description for the transit gateway.

Docker and Kubernetes Integration

Sat, 08 Apr 2023 00:00:00 +0000

Seamlessly integrate Docker containers with Kubernetes for scalable.

Understanding the Foundation

Understanding Docker and Kubernetes Integration

When I first started working with containers, I thought Docker and Kubernetes were competing technologies. That couldn’t be further from the truth. They’re actually perfect partners in the container ecosystem, each handling different aspects of the containerization journey.

Think of Docker as your master craftsman - it builds, packages, and runs individual containers with precision. Kubernetes, on the other hand, is like an orchestra conductor, coordinating hundreds or thousands of these containers across multiple machines to create a harmonious, scalable application.

How to Create an AWS EC2 Instance in Terraform

Fri, 07 Apr 2023 06:00:00 +0400

The following Terraform code snippet creates an EC2 instance for you.

provider "aws" {
  region = "us-west-2"
}

resource "aws_instance" "example" {
  ami           = "ami-0c94855ba95c71c99"  # Amazon Linux 2 AMI
  instance_type = "t2.micro"
  key_name      = "example-keypair"

  tags = {
    Name = "example-instance"
  }
}

In this example, we’re using the aws_instance resource type to create an EC2 instance in the us-west-2 region. We’re using the ami parameter to specify the Amazon Linux 2 AMI ID, and the instance_type parameter to specify a t2.micro instance type. We’re also specifying a key pair to use for SSH access with the key_name parameter.

A Primer on Terraform Concepts

Thu, 06 Apr 2023 06:00:00 +0400

Terraform is an open-source tool for building, changing, and versioning infrastructure safely and efficiently. It allows you to describe your infrastructure as code and manage it in a version-controlled way, just like you would with application code.

Here are the basic steps of how Terraform works:

Write your infrastructure code: You write infrastructure code in the Terraform configuration language (HCL) to describe the resources you want to create. You can define resources like servers, load balancers, databases, and more, as well as their configurations and relationships.

How to Learn Recursion by Example in Python

Wed, 05 Apr 2023 06:00:00 +0400

Here’s an example code in Python that demonstrates recursion:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

print(factorial(5))  # Output: 120

This code defines a function factorial that calculates the factorial of a given number n. The factorial of a number is the product of all positive integers up to and including that number. For example, the factorial of 5 is 5 x 4 x 3 x 2 x 1 = 120.

Understanding Site Reliability Engineering (SRE)

Tue, 04 Apr 2023 06:00:00 +0400

Site Reliability Engineering (SRE) can also help organizations to be more proactive in identifying and addressing potential issues before they become major problems. By monitoring system performance and using data-driven insights, SRE teams can detect and respond to issues more quickly, reducing the impact on customers and the business. This can help to increase uptime and reduce the cost of downtime, which can have a direct impact on revenue and profitability.

What is DevOps?

Mon, 03 Apr 2023 06:00:00 +0400

DevOps is a term that combines “development” and “operations.” It is a methodology that aims to bridge the gap between the software development and IT operations teams. DevOps is a set of practices that focuses on automating the software development process, reducing the time between writing code and deploying it to production, and ensuring a high level of quality in the delivered software.

Introduction to DevOps

DevOps is a set of practices that combines software development and IT operations. The goal of DevOps is to shorten the system’s development cycle and provide more reliable software releases. It is a methodology that aims to bridge the gap between the software development and IT operations teams. DevOps is a culture that emphasizes communication and collaboration between teams.

How to Create a Password Generator in Golang

Sun, 02 Apr 2023 06:00:00 +0400

Introduction

In today’s digital age, password security is more important than ever before. Hackers can easily guess weak passwords, leading to identity theft and other cybersecurity breaches. To ensure our online safety, we need to use strong and secure passwords that are difficult to guess. A good password generator can help us create random and strong passwords. In this blog post, we’ll discuss how to create a password generator in Golang.

How does Disaster Recovery work in the Cloud?

Sat, 01 Apr 2023 06:00:00 +0400

Disaster Recovery (DR) in the cloud refers to the process of recovering IT infrastructure and data in the event of a disaster, such as a natural disaster or a cyber attack, in a cloud environment. Cloud-based Disaster Recovery (DR) is different from traditional DR because it utilizes cloud services and technologies to protect data and applications and minimize downtime.

Some key elements involved in implementing a Disaster Recovery plan in the cloud covers topics such as the following.

What is DevOps and why is it important?

Fri, 31 Mar 2023 06:00:00 +0400

DevOps is a software development methodology that emphasizes collaboration and communication between software developers and IT operations teams. It is a set of practices that seeks to streamline the software development lifecycle, from planning and coding to testing and deployment, through the use of automation, monitoring, and iterative development processes.

The primary goal of DevOps is to deliver software more quickly, reliably, and efficiently by breaking down silos between development and operations teams and encouraging continuous feedback and improvement. By aligning development and operations teams, DevOps seeks to reduce time-to-market, improve software quality, and enhance overall business agility.

Docker Fundamentals: Containerization Basics

Fri, 31 Mar 2023 00:00:00 +0000

Learn the essential concepts and practical skills needed to containerize applications using Docker, from basic commands to production-ready deployments.

Introduction and Setup

Introduction to Docker and Containerization

Docker revolutionizes application deployment by packaging applications and their dependencies into lightweight, portable containers that run consistently across different environments.

What is Docker?

Docker is a containerization platform that allows you to package applications with all their dependencies into portable containers. Think of containers as lightweight, standalone packages that include everything needed to run an application: code, runtime, system tools, libraries, and settings.

What is the Zen of Python?

Thu, 30 Mar 2023 06:00:00 +0400

The Zen of Python is an Easter Egg that long time Pythoneer (Tim Peters) channeled the guiding principals for the language’s design principals into 20 aphorisms, of which only 19 of them are written down.

How to access this `Zen of Python` Easter Egg

By importing this into your Python application, it will immediately print as follows:

import this

What is the `Zen of Python`?

Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren’t special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one– and preferably only one –obvious way to do it. Although that way may not be obvious at first unless you’re Dutch. Now is better than never. Although never is often better than right now. If the implementation is hard to explain, it’s a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea – let’s do more of those!

Bash: Convert HTML to Markdown Recursively with Pandoc

Wed, 29 Mar 2023 06:00:00 +0400

You can recursively convert all your HTML files to Mardown format in Bash, by using Pandoc.

find . \-name "*.ht*" | while read i; do pandoc -f html -t markdown "$i" -o "${i%.*}.md"; done

How to Create a Password Generator in C++

Mon, 27 Mar 2023 06:00:00 +0400

You can easily create a password generator in C++ with the following simple method.

How to create the Password Generator in C++

#include <iostream>
#include <string>
#include <algorithm>
#include <random>

std::string generate_password(int length = 16) {
    std::string seed = string("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") + string("0123456789") + string("!@#$%^&*()_+=-{}[]\\|:;<>,.?/");

    std::string password_string = seed;
    std::shuffle(password_string.begin(), password_string.end(), std::mt19937{std::random_device{}()});
    return password_string.substr(0, length);
}

int main() {
    std::cout << generate_password() << std::endl;
    std::cout << generate_password(28) << std::endl;
    return 0;
}

How do you architect Disaster Recovery in AWS?

Sun, 26 Mar 2023 06:00:00 +0400

Disaster recovery (DR) in AWS involves creating a plan and set of procedures to help your organization recover from a catastrophic event, such as a natural disaster, power outage, or cyber attack, that could impact your business operations. AWS provides a range of tools and services to help you architect an effective DR solution in the cloud.

Here are the high-level steps to architect a Disaster Recovery solution in AWS:

What options exist for Infrastructure as Code (IaC)

Sat, 25 Mar 2023 06:00:00 +0400

There are several options for Infrastructure as Code (IaC) tools that can help automate the provisioning and management of infrastructure resources, such as servers, networks, and storage, in a reliable and reproducible way. Here are some of the most popular IaC options:

Terraform: An open-source tool by HashiCorp that supports a wide range of infrastructure providers, including AWS, Azure, Google Cloud, and more. Terraform uses a declarative language to describe infrastructure as code and can manage both low-level and high-level resources.

How to learn Java in 1 day

Fri, 24 Mar 2023 06:00:00 +0400

Learning Java in one day is not a realistic goal, as Java is a complex programming language that requires time and practice to master. However, here are some tips to get you started:

Start with the basics: Before diving into complex topics, learn the basics of Java, such as variables, data types, control structures, and object-oriented programming principles.
Watch tutorials and read documentation: There are many resources available online that can help you learn Java quickly. Watch video tutorials and read documentation to gain a basic understanding of the language.

How to read user input as numbers in Python

Thu, 23 Mar 2023 06:00:00 +0400

In Python 3 onwards, the input function returns a string type..

`int` value

You can explicitly convert this into an int type.

val = int(input("Enter a number: "))

`float` value

If you need to accept fractional components, then simply swap this out with a float type:

val = float(input("Enter a number:"))

`map` multiple values

If you have multiple integers in a single line, then you can use map to extract them into a list:

Capitalize First Letter of Each Word in Python

Wed, 22 Mar 2023 06:00:00 +0400

If you have a sentence containing multiple words, and you want each of the words to start with a capital letter, then you can do one of the following:

Option 1 - using `string.capwords()`

import string

string.capwords('this is a test!')

Output: 'This Is A Test!'

Option 2 - using `title()`

'this is a test!'.title()

Output: 'This Is A Test!'

Option 3 - using `join()`, `split()` and `list comprehensions`

" ".join(w.capitalize() for w in 'this is a test!'.split())

Output: 'This Is A Test!'

How to Create a Password Generator in Python

Thu, 16 Mar 2023 06:00:00 +0400

You can easily create a password generator in Python with the following simple method.

How to create the Password Generator in Python

import string
import random

def generate_password(length=16):
    seed = f"{string.ascii_letters}{string.ascii_lowercase}{string.ascii_uppercase}{string.punctuation}"

    password_string = [x for x in seed]
    random.shuffle(password_string)
    return ''.join(password_string[:length])

How to use the Password Generator in Python

With this function, you can either call the generate_password() function without any arguments, and it will generate a 16 digit long password, unless you need a longer one, then pass in an integer to specify the lengh of the password you would like. e.g. generate_password(28).

GitOps Workflow Implementation

Wed, 15 Mar 2023 00:00:00 +0000

Implement GitOps practices for infrastructure and application deployment using Git as the single source of truth for declarative infrastructure and applications.

Understanding GitOps: Core Principles and Benefits

Before diving into implementation details, let’s establish a clear understanding of GitOps principles and benefits.

Core GitOps Principles

GitOps is built on four fundamental principles:

Declarative Configuration: The entire system is described declaratively, typically using YAML or JSON files that specify the desired state.

How to Convert Bytes to a String in Python

Tue, 14 Mar 2023 06:00:00 +0400

If you need to convert bytes to a string in Python, then you can do the following:

your_string = b'This works \xE2\x9C\x85'.decode("utf-8")
print(your_string)

Output:

This works ✅

Note that in the above example, we have converted a utf-8 string to.

How to measure the elapsed time in Python

Mon, 13 Mar 2023 06:00:00 +0400

Option 1 - using the `time` module

import time

start = time.time()

print(23*2.3)

end = time.time()
print(end - start)

Output:

52.9
3.600120544433594e-05

Option 2 - using the `timeit` module

from timeit import default_timer as timer

start = timer()

print(23*2.3)

end = timer()
print(end - start)

Output:

52.9
6.355400000000039e-05

How to Change a MariaDB/MySQL Data Directory to a New Location on Linux

Tue, 07 Mar 2023 06:00:00 +0400

Step 1 — Moving the MariaDB Data Directory

mysql -u root -p

select @@datadir;

Output:
  +-----------------+
  | @@datadir       |
  +-----------------+
  | /var/lib/mysql/ |
  +-----------------+
  1 row in set (0.00 sec)

exit

sudo systemctl stop mariadb
sudo systemctl status mariadb

Output:
  mysql systemd[1]: Stopped MariaDB database server.

sudo rsync -av /var/lib/mysql /mnt/my-volume-01

sudo mv /var/lib/mysql /var/lib/mysql.bak

Step 2 — Pointing to the New Data Location

sudo vi /etc/my.cnf

[mysqld]
. . .
datadir=/mnt/my-volume-01/mysql
socket=/mnt/my-volume-01/mysql/mysql.sock
. . .

[client]
port=3306
socket=/mnt/my-volume-01/mysql/mysql.sock

!includedir /etc/my.cnf.d

Step 3 — Restarting MariaDB

sudo systemctl start mariadb
sudo systemctl status mariadb

mysql -u root -p

select @@datadir;

Output
+----------------------------+
| @@datadir                  |
+----------------------------+
| /mnt/my-volume-01/mysql/ |
+----------------------------+
1 row in set (0.01 sec)

exit

Cleanup

sudo rm -Rf /var/lib/mysql.bak

[Solved] Docker Daemon Connection Error: Daemon Running?

Sat, 04 Mar 2023 06:00:00 +0400

If you get the following error when trying to run a Docker container:

Cannot connect to the Docker daemon at unix:/var/run/docker.sock. Is the docker daemon running?

Then you can resolve it by running the following:

systemctl start docker

If this doesn’t work because of a root user issue, then you can do the following first:

gpasswd -a $USER docker

Additional issues?

Issue 1

If you have tried the above, and get this error:

[Solved] M1 Docker Image Platform Mismatch with Host (ARM64)

Fri, 03 Mar 2023 06:00:00 +0400

If you get the following error when trying to run a Docker container that was built on an M1 mac:

M1 docker preview and keycloak 'image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8)' Issue

The solution

Then you can do simply add the following argument to your docker build command.

--platform linux/amd64

Where this goes

docker build --platform linux/amd64 -t your_docker_item .

How to get the SHA512 sum of a string using Python

Thu, 02 Mar 2023 06:00:00 +0400

If you need to get the SHA512 sum of a string using Python, then you can do the following.

Step 1

Firstly, we need to use the hashlib module:

import hashlib

Step 2

Now make sure that the input string is encoded correctly.

your_input = "this is your input string".encode('utf-8')

Step 3

Finally use the sha512 function of the hashlib module, and get the hexdigest() value from it:

hashlib.sha512(your_input).hexdigest()

Putting it all together

import hashlib

your_input = "this is your input string".encode('utf-8')
hashed = hashlib.sha512(your_input).hexdigest()

print(hashed)

# --> 74cf60b5a22c401454e36193a65e7efeb5a7d72db9e1f786975e7bd2b7bdd12dee83f99e78542d0eca5c9152f09f397d0ac8de68275ca353837b28f938e429f4

How to get the SHA256 sum of a string using Python

Wed, 01 Mar 2023 06:00:00 +0400

If you need to get the SHA256 sum of a string using Python, then you can do the following.

Step 1

Firstly, we need to use the hashlib module:

import hashlib

Step 2

Now make sure that the input string is encoded correctly.

your_input = "this is your input string".encode('utf-8')

Step 3

Finally use the sha256 function of the hashlib module, and get the hexdigest() value from it:

hashlib.sha256(your_input).hexdigest()

Putting it all together

import hashlib

your_input = "this is your input string".encode('utf-8')
hashed = hashlib.sha256(your_input).hexdigest()

print(hashed)

# --> f7dc376447dcd13fdd6cb2aa20a2327bed1f8a1f3420d52c6fdb55b2b94d9b8e

How to get the MD5 sum of a string using Python

Tue, 28 Feb 2023 06:00:00 +0400

If you need to get the MD5 sum of a string using Python, then you can do the following.

Step 1

Firstly, we need to use the hashlib module:

import hashlib

Step 2

Now make sure that the input string is encoded correctly.

your_input = "this is your input string".encode('utf-8')

Step 3

Finally use the md5 function of the hashlib module, and get the hexdigest() value from it:

hashlib.md5(your_input).hexdigest()

Putting it all together

import hashlib

your_input = "this is your input string".encode('utf-8')
hashed = hashlib.md5(your_input).hexdigest()

print(hashed)

# --> af0874120fd6196ea1feeebdb6de0e54

[Solved] TypeError: datetime Not JSON Serializable

Mon, 27 Feb 2023 06:00:00 +0400

If you get the following error:

TypeError: Object of type datetime is not JSON serializable

..then you can solve it by using this trick:

json.dumps(your_dict, indent=4, sort_keys=True, default=str)

Microservices Monitoring and Observability

Sat, 25 Feb 2023 00:00:00 +0000

Build comprehensive monitoring.

Understanding Microservices Observability

The Observability Challenge

Why monitoring microservices is fundamentally different:

Distributed Complexity:

Multiple independent services with their own lifecycles
Complex service dependencies and interaction patterns
Polyglot environments with different languages and frameworks
Dynamic infrastructure with containers and orchestration
Asynchronous communication patterns

Traditional Monitoring Limitations:

Host-centric monitoring insufficient for containerized services
Siloed monitoring tools create incomplete visibility
Static dashboards can’t adapt to dynamic environments
Lack of context across service boundaries
Difficulty correlating events across distributed systems

Observability Requirements:

How to Return a List of All AWS Lambda Function Names in CLI

Fri, 24 Feb 2023 06:00:00 +0400

If you would like to list all AWS Lambda Function Names in your CLI using the AWS CLI, then you can do this:

Get a List of all Lambda Functions

aws lambda list-functions

However, note that this will return a potentially large JSON payload back to your CLI. So what if you only want a list of the function names themselves?

You can couple the AWS command above, with the jq command as follows:

How much faster is Python code?

Thu, 23 Feb 2023 06:00:00 +0400

The speed of Python code compared to other programming languages depends on a variety of factors, such as the specific task being performed, the libraries and frameworks used, the quality of the code implementation, and the hardware on which the code is executed.

In general, Python is an interpreted language, which means that code is executed line-by-line by an interpreter, rather than being compiled into machine code beforehand. This can make Python code slower than compiled languages like C or C++ for some tasks.

Containerization Best Practices for DevOps

Thu, 23 Feb 2023 00:00:00 +0000

Master containerization strategies.

Container Fundamentals and Docker Basics

Containers transformed how I think about application deployment. After years of wrestling with “it works on my machine” problems, containers finally gave us a way to package applications with their entire runtime environment.

Why Containers Matter

Traditional deployment meant installing applications directly on servers, managing dependencies, and hoping everything worked together. I’ve seen production outages caused by a missing library version or conflicting Python packages. Containers solve this by packaging everything your application needs into a single, portable unit.

Zip & Encode Dict to String & Back in Python

Wed, 22 Feb 2023 06:00:00 +0400

If you have a Python dictionary, and want to encode it as a string and zip it to save space, perhaps for passing a dictionary through as an environment variable or similar, then you can do the following

Zip then Encode / Decode then Unzip Functions

import json, gzip, base64
from io import BytesIO


def _zip_then_encode(data: dict) -> str:
    """Gzip and base64 encode a dictionary"""
    if type(data) != dict:
        raise TypeError("data must be a dictionary")
    compressed = BytesIO()
    with gzip.GzipFile(fileobj=compressed, mode="w") as f:
        json_response = json.dumps(data)
        f.write(json_response.encode("utf-8"))
    return base64.b64encode(compressed.getvalue()).decode("ascii")

def _decode_then_unzip(data) -> dict:
    res = base64.b64decode(data)
    res = gzip.decompress(res)
    res = res.decode("utf-8")
    res = json.loads(res)
    return res

To use the encode and decode functions, you can do the following:

MLOps Best Practices: Operationalizing Machine Learning at Scale

Sat, 18 Feb 2023 00:00:00 +0000

Comprehensive guide to MLOps covering model development.

MLOps Fundamentals

The ML Lifecycle

Understanding the end-to-end machine learning process:

ML Lifecycle Stages:

Problem definition and scoping
Data collection and preparation
Feature engineering and selection
Model development and training
Model evaluation and validation
Model deployment and serving
Monitoring and maintenance
Continuous improvement

MLOps vs. Traditional DevOps:

Data and model versioning (not just code)
Experiment tracking and reproducibility
Model-specific testing requirements
Specialized deployment patterns
Performance monitoring beyond uptime
Retraining workflows

MLOps Maturity Levels:

What Categories of Websites are there?

Fri, 17 Feb 2023 06:00:00 +0400

There are many different categories of websites, but here are some of the most common:

E-commerce websites: These websites sell products or services online. Examples include Amazon, eBay, and Etsy.
News websites: These websites provide up-to-date news and information on a variety of topics. Examples include CNN, BBC, and The New York Times.
Blogging websites: These websites are used for personal or business blogs. Examples include WordPress, Blogger, and Medium.

How to Generate a Random Number between 2 numbers in Python

Thu, 16 Feb 2023 06:00:00 +0400

If you need to generate a random number between two (2) numbers in Python, then you can make use of the random module.

First, import the module:

import random

Then you can use it like this:

random.randint(0, 255)

Another option is to use randrange and uniform as follows:

from random import randrange, uniform

# randrange gives you an integral value
irand = randrange(0, 10)

# uniform gives you a floating-point value
frand = uniform(0, 10)

How to Install AWS SAM CLI on Mac

Wed, 15 Feb 2023 06:00:00 +0400

If you need to install AWS SAM CLI on a Mac, then the easiest option is to use Homebrew with the following commands:

brew tap aws/tap
brew install aws-sam-cli

Now you can validate the installation as follows:

sam --version

How to count the amount of rows in MariaDB fast

Sat, 11 Feb 2023 06:00:00 +0400

If you need to find the fastest way to count the number of rows in a massive MariaDB, or MySQL table, then you can do the following instead of performing a select count() query:

show table status like '<TABLE_NAME>'

This will provide you with a table of information about the table statistics, including the amount of rows.

How to find the Product of Consecutive Fib Numbers in Python

Fri, 10 Feb 2023 06:00:00 +0400

0, 0, 1, 0, 2, 0, 2, 2, 1, 6, 0, 5, 0, 2, 6, 5, 4, 0, 5, 3, 0, 3, …

This is the Van Eck’s Sequence.

Let’s go through it step by step.

Term 1: The first term is 0. Term 2: Since we haven’t seen 0 before, the second term is 0. Term 3: Since we had seen a 0 before, one step back, the third term is 1 Term 4: Since we haven’t seen a 1 before, the fourth term is 0 Term 5: Since we had seen a 0 before, two steps back, the fifth term is 2. And so on…

How to Solve Van Eck's Sequence in Python

Thu, 09 Feb 2023 06:00:00 +0400

0, 0, 1, 0, 2, 0, 2, 2, 1, 6, 0, 5, 0, 2, 6, 5, 4, 0, 5, 3, 0, 3, …

This is the Van Eck’s Sequence.

Let’s go through it step by step.

How to Solve: Help the Bookseller Challenge in Python

Wed, 08 Feb 2023 16:20:00 +0400

A bookseller has lots of books classified in 26 categories labeled A, B, … Z. Each book has a code c of 3, 4, 5 or more characters. The 1st character of a code is a capital letter which defines the book category.

In the bookseller’s stocklist each code c is followed by a space and by a positive integer n (int n >= 0) which indicates the quantity of books of this code in stock.

How to solve AWS MediaPackage PackagingGroup Quota Limit

Tue, 31 Jan 2023 00:05:00 +0400

If you are using AWS Elemental MediaPackage and hit the following error, then you need to either do one of the following:

Error: error waiting for CloudFormation Stack (arn:aws:cloudformation:eu-west-1:800417762774:stack/dev-MediaPackage-Vod-1/511fc7a0-a092-11ed-b853-068baf6ac251) create: failed to create CloudFormation stack, delete requested (DELETE_COMPLETE): ["The following resource(s) failed to create: [PackagingGroup]. Delete requested by user." "Resource handler returned message: \"Limit exceeded for resource of type 'AWS::MediaPackage::PackagingGroup'. Reason: You reached the quota for resource=PackagingGroup. Delete the resources that you don?t need, or request a quota increase. (Service: MediaPackageVod, Status Code: 429, Request ID: bc7a5f31-463e-4ac6-a9a2-438111dd201c)\" (RequestToken: 135f9266-ddcd-1b8d-fdff-00e3837d5dc3, HandlerErrorCode: ServiceLimitExceeded)"]

How to Run Cdk Bootstrap

Mon, 30 Jan 2023 12:07:19 +0400

To bootstrap an AWS CDK environment, you simply need to do the following:

npx aws-cdk bootstrap

…for each environment that you would like the CD to operate within.

This will deploy all the required prerequisites to the AWS account, such as the:

An Amazon S3 bucket for storing files and IAM roles that grant permissions needed to perform deployments.
The required resources are defined in an AWS CloudFormation stack, called the bootstrap stack, which is usually named CDKToolkit. Like any AWS CloudFormation stack, it appears in the AWS CloudFormation console once it has been deployed.

How to Get Account Number from AWS Lambda

Tue, 24 Jan 2023 05:16:43 +0000

If you need to get the current Account Number, or Account ID from within a Lambda execution, then you can access invoked_function_arn from the context and return the associated value as follows:

aws_account_id = context.invoked_function_arn.split(":")[4]

Building Resilient Distributed Systems

Fri, 20 Jan 2023 00:00:00 +0000

Learn fault tolerance patterns.

Understanding Distributed Systems Failures

Failure Modes and Models

Recognizing what can go wrong:

Common Failure Modes:

Hardware failures
Network partitions
Service dependencies failures
Resource exhaustion
Data corruption
Clock skew
Configuration errors
Deployment failures
Cascading failures
Thundering herd problems

The Fallacies of Distributed Computing:

The network is reliable
Latency is zero
Bandwidth is infinite
The network is secure
Topology doesn’t change
There is one administrator
Transport cost is zero
The network is homogeneous

Failure Models:

Summary of the Frequently Used AWS STS API calls

Thu, 19 Jan 2023 00:05:00 +0000

AssumeRole – is useful for allowing existing IAM users to access AWS resources that they don’t already have access to. For example, the user might need access to resources in another AWS account. It is also useful as a means to temporarily gain privileged access—for example, to provide multi-factor authentication (MFA). You must call this API using existing IAM user credentials.

AssumeRoleWithWebIdentity – returns a set of temporary security credentials for federated users who are authenticated through a public identity provider. Examples of public identity providers include Login with Amazon, Facebook, Google, or any OpenID Connect (OIDC)-compatible identity provider.

Understanding Locking and Conditional Writes in AWS DynamoDB

Wed, 18 Jan 2023 00:05:00 +0000

Optimistic locking is a strategy to ensure that the client-side item that you are updating (or deleting) is the same as the item in DynamoDB. Optimistic concurrency depends on checking a value upon save to ensure that it has not changed. If you use this strategy, then your database writes are protected from being overwritten by the writes of others — and vice-versa.

By default, the DynamoDB write operations (PutItem, UpdateItem, DeleteItem) are unconditional: each of these operations will overwrite an existing item that has the specified primary key.

AWS CodeDeploy Deployment Type Options

Tue, 17 Jan 2023 00:05:00 +0000

CodeDeploy provides two (2) deployment type options:

Option 1 – In-place Deployment

In-place deployment: The application on each instance in the deployment group is stopped, the latest application revision is installed, and the new version of the application is started and validated. You can use a load balancer so that each instance is deregistered during its deployment and then restored to service after the deployment is complete. Only deployments that use the EC2/On-Premises compute platform can use in-place deployments. AWS Lambda compute platform deployments cannot use an in-place deployment type.

Defining Amazon ECS Task Placement Strategies

Mon, 16 Jan 2023 00:05:00 +0000

Amazon ECS supports the following task placement strategies:

binpack – Place tasks based on the least available amount of CPU or memory. This minimizes the number of instances in use.

random – Place tasks randomly.

spread – Place tasks evenly based on the specified value. Accepted values are attribute key-value pairs, instanceId, or host.

Deployment methods in AWS Elastic Beanstalk

Sun, 15 Jan 2023 14:51:26 +0000

– All at once – Deploy the new version to all instances simultaneously. All instances in your environment are out of service for a short time while the deployment occurs.

– Rolling – Deploy the new version in batches. Each batch is taken out of service during the deployment phase, reducing your environment’s capacity by the number of instances in a batch.

– Rolling with additional batch – Deploy the new version in batches, but first launch a new batch of instances to ensure full capacity during the deployment process.

How to update NTP to sync clock on Linux

Wed, 04 Jan 2023 07:44:07 +0000

If you need to sync the clock on Linux using the central NTP clock service, you can do the following:

sudo service ntp stop
sudo ntpd -gq
sudo service ntp start

The -gg flags do the following:

Tell g flag tells the NTP Daemon to correct the time regardless of the offset
The q flag tells it to exit immediately after setting the time

Data Partitioning Strategies for Distributed Systems

Mon, 26 Dec 2022 00:00:00 +0000

Master data partitioning techniques including sharding.

Understanding Data Partitioning

Data partitioning (also known as sharding) is the process of breaking a large dataset into smaller, more manageable pieces called partitions or shards. Each partition contains a subset of the data and can be stored on a separate database server or node.

Why Partition Data?

Scalability: Overcome hardware limitations by distributing data across multiple machines
Performance: Improve query performance through parallel processing across partitions
Availability: Enhance system resilience by isolating failures to specific partitions
Manageability: Make maintenance operations like backups and index rebuilds more efficient
Data Locality: Store data close to the users or services that access it most frequently

Partitioning vs. Replication

It’s important to distinguish between partitioning and replication:

Distributed Consensus Algorithms: Building Fault-Tolerant Systems

Mon, 19 Dec 2022 00:00:00 +0000

Master the algorithms that enable distributed systems to agree on shared state despite failures and network partitions.

The Consensus Problem

Before diving into specific algorithms, let’s clearly define the consensus problem. In a distributed system with multiple nodes, consensus is the process of agreeing on a single value or state among all non-faulty nodes. A correct consensus algorithm must satisfy the following properties:

Agreement: All non-faulty nodes decide on the same value.
Validity: If all nodes propose the same value, then all non-faulty nodes decide on that value.
Termination: All non-faulty nodes eventually decide on some value.

The challenge is achieving these properties in the presence of:

How to Find IP Address Ranges used by Amazon S3

Tue, 13 Dec 2022 00:05:00 +0000

You can query the ip-ranges Amazon AWS URL, and parse the results through jq as follows:

Generic S3 IP Ranges

Query:

curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq -r '.prefixes[] | select(.service=="S3")'

Response:

{
  "ip_prefix": "3.5.140.0/22",
  "region": "ap-northeast-2",
  "service": "S3",
  "network_border_group": "ap-northeast-2"
}
{
  "ip_prefix": "52.219.170.0/23",
  "region": "eu-central-1",
  "service": "S3",
<truncated>

Region Specific S3 IP Ranges

Query:

curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq -r '.prefixes[] | select(.region=="eu-west-1") | select(.service=="S3") | .ip_prefix'

Response:

18.34.32.0/20
3.5.72.0/23
52.218.0.0/17
3.5.64.0/21
52.92.0.0/17
18.34.240.0/22
3.251.110.208/28
3.251.110.224/28

How to Find the nth Reverse Number in Java

Mon, 12 Dec 2022 00:05:00 +0000

The challenge

Reverse Number is a number which is the same when reversed.

For example, the first 20 Reverse Numbers are:

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101

Task

You need to return the nth reverse number. (Assume that reverse numbers start from 0 as shown in the example.)

Notes

1 < n <= 100000000000

The solution in Java

Option 1:

How to Find the Sum of Intervals in Java

Sun, 11 Dec 2022 00:05:00 +0000

The challenge

Write a function called sumIntervals/sum_intervals() that accepts an array of intervals, and returns the sum of all the interval lengths. Overlapping intervals should only be counted once.

Intervals

Intervals are represented by a pair of integers in the form of an array. The first value of the interval will always be less than the second value. Interval example: [1, 5] is an interval from 1 to 5. The length of this interval is 4.

How to Find the Stray Number in Python

Sat, 10 Dec 2022 00:05:00 +0000

The challenge

You are given an odd-length array of integers, in which all of them are the same, except for one single number.

Complete the method which accepts such an array, and returns that single different number.

The input array will always be valid! (odd-length >= 3)

Examples

[1, 1, 2] ==> 2
[17, 17, 3, 17, 17, 17, 17] ==> 3

The solution in Python

Option 1:

def stray(arr):
    for x in arr:
        if arr.count(x) == 1:
            return x

Option 2:

How to Find the EDID UUID of External Mac Monitors

Fri, 09 Dec 2022 00:05:00 +0000

You can issue the following command on an Apple Mac’s terminal to show the EDID UUID (unique serial number) of all attached external monitors:

ioreg -l | grep EDID

[Solved] jsii.errors.JSIIError: docker exited with status 1

Thu, 08 Dec 2022 00:05:00 +0000

If you get the following error while running AWS CDK:

raise JSIIError(resp.error) from JavaScriptError(resp.stack)
jsii.errors.JSIIError: docker exited with status 1

Then you can resolve it as follows:

How to solve `docker exited with status 1` error

Make sure that your local Docker client is running.

Start docker on the local machine and CDK will be able to make the Docker connections required.

How to Filter a Number in C

Wed, 07 Dec 2022 00:05:00 +0000

The challenge

The number has been mixed up with the text. Your goal is to retrieve the number from the text, can you return the number back to its original state?

Task

Your task is to return a number from a string.

Details

You will be given a string of numbers and letters mixed up, you have to return all the numbers in that string in the order they occur.

How to Take a Ten Minute Walk in C

Tue, 06 Dec 2022 00:05:00 +0000

The challenge

You live in the city of Cartesia where all roads are laid out in a perfect grid. You arrived ten minutes too early to an appointment, so you decided to take the opportunity to go for a short walk. The city provides its citizens with a Walk Generating App on their phones — everytime you press the button it sends you an array of one-letter strings representing directions to walk (eg. [‘n’, ‘s’, ‘w’, ‘e’]). You always walk only a single block for each letter (direction) and you know it takes you one minute to traverse one city block, so create a function that will return true if the walk the app gives you will take you exactly ten minutes (you don’t want to be early or late!) and will, of course, return you to your starting point. Return false otherwise.

How to Count Stats of a String in C

Mon, 05 Dec 2022 00:05:00 +0000

The challenge

You will be given a string and your task will be to return a list of ints detailing the count of uppercase letters, lowercase, numbers and special characters, as follows.

Solve("*'&ABCDabcde12345") = [4,5,5,3]. 
--the order is: uppercase letters, lowercase, numbers and special characters.

The solution in C

Option 1:

void count_char_types (const char *string, unsigned counts[4])
{
  char c;
  counts[0] = counts[1] = counts[2] = counts[3] = 0;
  while((c = *string++))
    if(c >= 'A' && c <= 'Z') counts[0]++;
    else if(c >= 'a' && c <= 'z') counts[1]++;
    else if(c >= '0' && c <= '9') counts[2]++;
    else counts[3]++;
}

Option 2:

How to Convert a String to the NATO Phonetic Alphabet in C

Sun, 04 Dec 2022 00:05:00 +0000

The challenge

You’ll have to translate a string to Pilot’s alphabet (NATO phonetic alphabet).

Input:

If, you can read?

Output:

India Foxtrot , Yankee Oscar Uniform Charlie Alfa November Romeo Echo Alfa Delta ?

Note:

There are preloaded dictionary you can use, named NATO
The set of used punctuation is ,.!?.
Punctuation should be kept in your return string, but spaces should not.
Xray should not have a dash within.
Every word and punctuation mark should be seperated by a space ‘ ‘.
There should be no trailing whitespace

The solution in C

Option 1:

How to Add 1 to the Value of each Array in C

Sat, 03 Dec 2022 00:05:00 +0000

The challenge

Given an array of integers of any length, return an array that has 1 added to the value represented by the array.

the array can’t be empty
only non-negative, single digit integers are allowed

Return nil (or your language’s equivalent) for invalid inputs.

Examples:

Valid arrays

[4, 3, 2, 5] would return [4, 3, 2, 6]
[1, 2, 3, 9] would return [1, 2, 4, 0]
[9, 9, 9, 9] would return [1, 0, 0, 0, 0]
[0, 1, 3, 7] would return [0, 1, 3, 8]

How to Calculate the Sum of a Sequence in C

Fri, 02 Dec 2022 00:05:00 +0000

The challenge

Your task is to make function, which returns the sum of a sequence of integers.

The sequence is defined by 3 non-negative values: begin, end, step (inclusive).

If begin value is greater than the end, function should returns ****

Examples

2,2,2 --> 2
2,6,2 --> 12 (2 + 4 + 6)
1,5,1 --> 15 (1 + 2 + 3 + 4 + 5)
1,5,3  --> 5 (1 + 4)

The solution in C

Option 1:

How to Solve the Sum of Triangular Numbers in C

Thu, 01 Dec 2022 00:05:00 +0000

The challenge

Your task is to return the sum of Triangular Numbers up-to-and-including the nth Triangular Number.

Triangular Number: “any of the series of numbers (1, 3, 6, 10, 15, etc.) obtained by continued summation of the natural numbers 1, 2, 3, 4, 5, etc.”

[01]
02 [03]
04 05 [06]
07 08 09 [10]
11 12 13 14 [15]
16 17 18 19 20 [21]

e.g. If 4 is given: 1 + 3 + 6 + 10 = 20.

How to Determine if a String Only Contains Unique Characters in C

Wed, 30 Nov 2022 00:05:00 +0000

The challenge

Write a program to determine if a string contains only unique characters. Return true if it does and false otherwise.

The string may contain any of the 128 ASCII characters. Characters are case-sensitive, e.g. ‘a’ and ‘A’ are considered different characters.

The solution in C

Option 1:

int has_unique_chars(const char *str) {
  int mask[128]={0};
  while (*str) if (++mask[*str++]>1) return 0;
  return 1;
}

Option 2:

#include <limits.h>

_Bool has_unique_chars(const char *str) {
    char hit[CHAR_MAX + 1] = {0};
    while (*str) {
        if (*str < 0) { str++; continue; }
        if (hit[*str]) return 0;
        hit[*str++] = 1;
    }
    return 1;
}

Option 3:

How to Find the Maximum Multiple in C

Tue, 29 Nov 2022 00:05:00 +0000

The challenge

Given a Divisor and a Bound , Find the largest integer N , Such That ,

Conditions :

N is divisible by divisor
N is less than or equal to bound
N is greater than 0.

Notes

The parameters (divisor, bound) passed to the function are only positive values .
It’s guaranteed that a divisor is Found .Input » Output Examples

maxMultiple (2,7) ==> return (6)

Explanation:

(6) is divisible by (2) , (6) is less than or equal to bound (7) , and (6) is > 0 .

How to Assign a Digital Cypher in C

Mon, 28 Nov 2022 00:05:00 +0000

The challenge

Digital Cypher assigns to each letter of the alphabet unique number. For example:

 a  b  c  d  e  f  g  h  i  j  k  l  m
 1  2  3  4  5  6  7  8  9 10 11 12 13
 n  o  p  q  r  s  t  u  v  w  x  y  z
14 15 16 17 18 19 20 21 22 23 24 25 26

Instead of letters in encrypted word we write the corresponding number, eg. The word scout:

How to Check for All Inclusive in C

Sun, 27 Nov 2022 00:05:00 +0000

The challenge

Input:

a string strng
an array of strings arr

Output of function contain_all_rots(strng, arr) (or containAllRots or contain-all-rots):

a boolean true if all rotations of strng are included in arr
false otherwise

Examples:

contain_all_rots(
  "bsjq", ["bsjq", "qbsj", "sjqb", "twZNsslC", "jqbs"]) -> true

contain_all_rots(
  "Ajylvpy", ["Ajylvpy", "ylvpyAj", "jylvpyA", "lvpyAjy", "pyAjylv", "vpyAjyl", "ipywee"]) -> false)

Note:

Though not correct in a mathematical sense

we will consider that there are no rotations of strng == ""
and for any array arr: contain_all_rots("", arr) --> true

The solution in C

Option 1:

How to Solve for Factorial in C

Sat, 26 Nov 2022 00:05:00 +0000

The challenge

In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example: 5! = 5 * 4 * 3 * 2 * 1 = 120. By convention the value of 0! is 1.

Write a function to calculate factorial for a given input. If input is below 0 or above 12 return -1 (C).

How to Create an Incrementer in C

Fri, 25 Nov 2022 00:05:00 +0000

The challenge

Given an input of an array of digits, return the array with each digit incremented by its position in the array: the first digit will be incremented by 1, the second digit by 2, etc. Make sure to start counting your positions from 1 ( and not 0 ).

Your result can only contain single digit numbers, so if adding a digit with its position gives you a multiple-digit number, only the last digit of the number should be returned.

How to Return the Closest Number Multiple of 10 in C

Thu, 24 Nov 2022 00:05:00 +0000

The challenge

Given a number return the closest number to it that is divisible by 10.

Example input:

22
25
37

Expected output:

20
30
40

The solution in C

Option 1:

#include <math.h>

int round_to_10 (int n) {
  return round(n / 10.0) * 10;
}

Option 2:

int round_to_10(int n) {
  return (n + 5) / 10 * 10;
}

Option 3:

int round_to_10 (int n) {
    int r = n % 10;
    if (r > 0)
        return r < 5 ? n - r : n - r + 10;
    else if (r < 0)
        return r > -5 ? n - r : n - r - 10;
    return n;
}

Test cases to validate our solution

#include <criterion/criterion.h>

extern int round_to_10 (int n);
static void do_test (int n, int expected);

Test(tests_suite, sample_tests)
{
  do_test(0, 0);
  do_test(10, 10);
  do_test(22, 20);
  do_test(25, 30);
  do_test(37, 40);
}

static void do_test (int n, int expected)
{
  int actual = round_to_10(n);
  cr_assert_eq(actual, expected,
    "for n = %d, expected %d, but got %d",
    n, expected, actual
  );
}

How to Reverse Every Other Word in a String in C

Wed, 23 Nov 2022 00:05:00 +0000

The challenge

Reverse every other word in a given string, then return the string. Throw away any leading or trailing whitespace, while ensuring there is exactly one space between each word. Punctuation marks should be treated as if they are a part of the word in this challenge.

The solution in C

Option 1:

#include <stddef.h>
#include <stdbool.h>

void reverse_alternate(const char *string, char *result)
{
  bool is_word = false, is_second = false, not_first = false;
  for (const char *s = string; *s; ++s) {
    if (*s == ' ' && is_word) {
      is_word = false;
      is_second = !is_second;
    } else if (*s != ' ' && !is_word) {
      if (not_first) *result++ = ' ';
      is_word = not_first = true;
    }
    
    if (is_second && is_word) {
      size_t i = 0;
      for (const char *ss = s; *ss && *ss != ' '; ++ss, ++i)
        ;
      for (size_t j = 0; j < i; ++j)
        result[j] = s[i - j - 1];
      s += i - 1;
      result += i;
    } else if (*s != ' ')
      *result++ = *s;
  }
  *result = '\0';
}

Option 2:

How to Solve Simple Beads Count in C

Tue, 22 Nov 2022 00:05:00 +0000

The challenge

Two red beads are placed between every two blue beads. There are N blue beads. After looking at the arrangement below work out the number of red beads.

@ @@ @ @@ @ @@ @ @@ @ @@ @

How to Solve the Maze Runner in C

Mon, 21 Nov 2022 00:05:00 +0000

The challenge

Introduction

Task

The Maze array will look like

maze = [[1,1,1,1,1,1,1],
        [1,0,0,0,0,0,3],
        [1,0,1,0,1,0,1],
        [0,0,1,0,0,0,1],
        [1,0,1,0,1,0,1],
        [1,0,0,0,0,0,1],
        [1,2,1,0,1,0,1]]

..with the following key

  directions = "NNNNNEEEEE" == "Finish" // (directions passed as a string)

Rules

The solution in C

Option 1:

How to Take a Number and Sum It’s Digits Raied to the Consecutive Powers in C

Sun, 20 Nov 2022 00:05:00 +0000

The challenge

The number 89 is the first integer with more than one digit that fulfills the property partially introduced in the title of this challenge. What’s the use of saying “Eureka”? Because this sum gives the same number.

In effect: 89 = 8^1 + 9^2

The next number in having this property is 135.

See this property again: 135 = 1^1 + 3^2 + 5^3

We need a function to collect these numbers, that may receive two integers a, b that defines the range [a, b] (inclusive) and outputs a list of the sorted numbers in the range that fulfills the property described above.

How to Find the Middle Element in C

Sat, 19 Nov 2022 00:05:00 +0000

The challenge

You need to create a function that when provided with a triplet, returns the index of the numerical element that lies between the other two elements.

The input to the function will be an array of three distinct numbers (Haskell: a tuple).

For example:

gimme([2, 3, 1]) => 0

2 is the number that fits between 1 and 3 and the index of 2 in the input array is __.

How to Invite More Women in C

Fri, 18 Nov 2022 00:05:00 +0000

The challenge

Task

King Arthur and his knights are having a New Years party. Last year Lancelot was jealous of Arthur, because Arthur had a date and Lancelot did not, and they started a duel.

To prevent this from happening again, Arthur wants to make sure that there are at least as many women as men at this year’s party. He gave you a list of integers of all the party goers.

How to Build a Tower in C

Thu, 17 Nov 2022 00:05:00 +0000

The challenge

Build a pyramid-shaped tower, as an array/list of strings, given a positive integer number of floors. A tower block is represented with "*" character.

For example, a tower with 3 floors looks like this:

[
  "  *  ",
  " *** ", 
  "*****"
]

And a tower with 6 floors looks like this:

[
  "     *     ", 
  "    ***    ", 
  "   *****   ", 
  "  *******  ", 
  " ********* ", 
  "***********"
]

The solution in C

Option 1:

How to Calculate A Rule of Divisibility by 7 in C

Wed, 16 Nov 2022 00:05:00 +0000

The challenge

A number m of the form 10x + y is divisible by 7 if and only if x − 2y is divisible by 7. In other words, subtract twice the last digit from the number formed by the remaining digits. Continue to do this until a number known to be divisible by 7 is obtained; you can stop when this number has at most 2 digits because you are supposed to know if a number of at most 2 digits is divisible by 7 or not.

How to Categorize a New Member in C

Tue, 15 Nov 2022 00:05:00 +0000

The challenge

The Western Suburbs Croquet Club has two categories of membership, Senior and Open. They would like your help with an application form that will tell prospective members which category they will be placed.

To be a senior, a member must be at least 55 years old and have a handicap greater than 7. In this croquet club, handicaps range from -2 to +26; the better the player the lower the handicap.

Load Balancing Strategies for Distributed Systems

Tue, 15 Nov 2022 00:00:00 +0000

Master the art of distributing traffic efficiently across multiple servers and services in distributed architectures.

Understanding Load Balancing in Distributed Systems

Load balancing in distributed systems operates at multiple levels, from DNS-based global load balancing to application-level request distribution. Before diving into specific strategies, let’s understand the key objectives and challenges.

Key Objectives of Load Balancing

Even Distribution: Spread workload evenly across available resources
High Availability: Ensure service continuity even when some components fail
Scalability: Accommodate growing workloads by adding resources
Efficiency: Optimize resource utilization
Latency Reduction: Minimize response times for end users

Load Balancing Layers

Load balancing can be implemented at different layers of the system:

How to Solve Deodorant Evaporator in C

Mon, 14 Nov 2022 00:05:00 +0000

The challenge

This program tests the life of an evaporator containing a gas.

We know the content of the evaporator (content in ml), the percentage of foam or gas lost every day (evap_per_day) and the threshold (threshold) in percentage beyond which the evaporator is no longer useful. All numbers are strictly positive.

The program reports the nth day (as an integer) on which the evaporator will be out of use.

How to Find the Divisors in C

Sun, 13 Nov 2022 00:05:00 +0000

The challenge

Create a function named divisors/Divisors that takes an integer n > 1 and returns an array with all of the integer’s divisors(except for 1 and the number itself), from smallest to largest. If the number is prime return the string ‘(integer) is prime’ (null in C#) (use Either String a in Haskell and Result<Vec<u32>, String> in Rust).

Example:

divisors(12); // results in {2, 3, 4, 6}
divisors(25); // results in {5}
divisors(13); // results in NULL

The solution in C

Option 1:

Terraform State Management: Advanced Patterns and Best Practices

Sun, 13 Nov 2022 00:00:00 +0000

Terraform state is both the most critical and most dangerous aspect of infrastructure as code. It’s your source of truth for what exists, but it’s also a single point of failure that can lock teams out of their infrastructure or, worse, lead to accidental resource destruction.

This guide goes deep into state management patterns that work at scale, covering everything from basic remote backends to complex state migration strategies and disaster recovery procedures.

Solving Love vs Friendship in C

Sat, 12 Nov 2022 00:05:00 +0000

The challenge

If　a = 1, b = 2, c = 3 ... z = 26

Then l + o + v + e = 54

and f + r + i + e + n + d + s + h + i + p = 108

So friendship is twice as strong as love 🙂

Your task is to write a function which calculates the value of a word based off the sum of the alphabet positions of its characters.

Terraform Testing and Validation: Quality Infrastructure Code

Sat, 12 Nov 2022 00:00:00 +0000

Infrastructure code needs the same quality assurance practices as application code, but testing infrastructure presents unique challenges. How do you unit test a VPC? How do you validate that your security policies actually work? How do you catch configuration errors before they reach production?

This guide covers the complete spectrum of Terraform testing and validation, from static analysis and policy validation to integration testing with real cloud resources.

Static Analysis and Linting

Static analysis catches errors before you even run Terraform, identifying syntax issues, security problems, and style inconsistencies that could cause problems later. Unlike application code, infrastructure code mistakes can be expensive—literally. A misconfigured security group or an oversized instance type can cost money and create security vulnerabilities.

How to Bounce Balls in C

Fri, 11 Nov 2022 00:05:00 +0000

The challenge

A child is playing with a ball on the nth floor of a tall building. The height of this floor, h, is known.

He drops the ball out of the window. The ball bounces (for example), to two-thirds of its height (a bounce of 0.66).

His mother looks out of a window 1.5 meters from the ground.

How many times will the mother see the ball pass in front of her window (including when it’s falling and bouncing?

How to Find the Capitals in C

Thu, 10 Nov 2022 00:05:00 +0000

The challenge

Instructions

Write a function that takes a single string (word) as argument. The function must return an ordered list containing the indexes of all capital letters in the string.

Example

Test.assertSimilar( capitals('CodEStAr'), [0,3,4,6] );

The solution in C

Option 1:

#include <stddef.h>
#include <string.h>
#include <stdlib.h>

size_t *find_capitals(const char *word, size_t *nb_uppercase)
{
    size_t n = strlen(word);
    size_t *arr = (size_t *) calloc(n, sizeof(size_t));
    size_t j = 0;
    for(size_t i=0; i<n; i++) {
        if(word[i] >='A' && word[i] <='Z') {
            arr[j++] = i;
        }
    }
    *nb_uppercase = j;
    return realloc(arr, j * sizeof(size_t));
}

Option 2:

How to Empty and Delete an S3 Bucket using the AWS CLI

Wed, 09 Nov 2022 00:05:00 +0000

Option 1 – Using `AWS CLI`

Step 1

export bucketname='your-bucket-here'

Step 2

aws s3api delete-objects --bucket $bucketname --delete "$(aws s3api list-object-versions --bucket $bucketname --output=json --query='{Objects: *[].{Key:Key,VersionId:VersionId}}')";

Step 3

aws s3 rb s3://$bucketname

Option 2 – Using `Python`

#!/usr/bin/env python

BUCKET = 'your-bucket-here'

import boto3

s3 = boto3.resource('s3')
bucket = s3.Bucket(BUCKET)
bucket.object_versions.delete()

bucket.delete()

What ports to open for FSx connection to AWS Managed Active Directory

Tue, 08 Nov 2022 00:05:00 +0000

If you are creating a FSx file system, and want to connect it to AWS Managed Active Directory, then you will need to create a VPC Security Group with the following ports:

Inbound ports


Rules	Ports
UDP	53, 88, 123, 389, 464
TCP	53, 88, 123, 389, 445, 464, 636, 3268, 3269, 9389, 49152-65535

Outbound ports

All traffic, 0.0.0.0/0

Multi-Cloud Terraform: Managing Infrastructure Across Providers

Tue, 08 Nov 2022 00:00:00 +0000

Multi-cloud strategies are becoming increasingly common as organizations seek to avoid vendor lock-in, leverage best-of-breed services, and meet compliance requirements. However, managing infrastructure across multiple cloud providers introduces complexity in networking, identity management, monitoring, and operational processes.

This guide covers the patterns and practices for successfully implementing multi-cloud infrastructure with Terraform, from basic provider configuration to advanced cross-cloud networking and unified governance.

Multi-Provider Setup

Managing infrastructure across multiple cloud providers requires careful planning of provider configurations, authentication strategies, and resource organization. Each cloud provider has different authentication mechanisms, regional structures, and service offerings that need to be coordinated in a unified Terraform configuration.

How to Calculate Variance in Python

Mon, 07 Nov 2022 00:05:00 +0000

If you need to calculate variance in Python, then you can do the following.

Option 1 – Using `variance()` from `Statistics` module

import statistics

list = [12,14,10,6,23,31]
print("List : " + str(list))

var = statistics.variance(list)
print("Variance: " + str(var))

Option 2 – Using `var()` from `numpy` module

import numpy as np

arr = [12,43,24,17,32]

print("Array : ", arr)
print("Variance: ", np.var(arr))

Option 3 – Using `sum()` and `List Comprehensions`

list = [12,43,24,17,32]
average = sum(list) / len(list)
var = sum((x-average)**2 for x in list) / len(list)
print(var)

How to Calculate the Sum of a List in Python

Sun, 06 Nov 2022 00:05:00 +0000

If you need to calculate and get the sum of a list in Python, then you can do the following.

Option 1 – Using `sum()`

myList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
listSum = sum(myList)
print(f"Sum of list -> {listSum}")

If you get a TypeError then you can do the following:

myList = ["1", "3", "5", "7", "9"]
myNewList = [int(string) for string in myList]
sum1 = sum(myNewList)
sum2 = sum(number for number in myNewList)
print(f"Sum of list -> {sum1}")
print(f"Sum of list -> {sum2}")

Option 2 – Using `for`

myList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
length = len(myList)
listSum = 0

for i in range(length):
    listSum += myList[i]

print(f"Sum of list -> {listSum}")

How to add a List to a Set in Python

Sat, 05 Nov 2022 00:05:00 +0000

If you need to add a list to a set in Python, then you can do the following:

Option 1 – Using `Tuple`

myset = set((1,2,3,4))
mylist = list(1,2,3])

myset.add(tuple(mylist))
print(myset)

Output: {1, 2, 3, 4, (1, 2, 3)}

Option 2 – Using `set.update()`

myset = set((1,2,3,4))
mylist = list(8,9,12])

myset.update(tuple(mylist))
print(myset)

Output: {1, 2, 3, 4, 8, 9, 12}

How to Remove Punctuation from a List in Python

Fri, 04 Nov 2022 00:05:00 +0000

If you have a Python list, and want to remove all punctuation, then you can do the following:

First get all punctuation by using `string.punctuation`

import string
print(string.punctuation)

Output:

!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~

Option 1 – Using `for`

import string
words = ["hell'o", "Hi,", "bye bye", "good bye", ""]
new_words = []
for word in words:
    if word == "":
        words.remove(word)
    else:
        for letter in word:
            if letter in string.punctuation:
                word = word.replace(letter,"")   
        new_words.append(word)
print(new_words)

Option 2 – Using `List Comprehensions`

import string
words = ["hell'o", "Hi,", "bye bye", "good bye", ""]
words = [''.join(letter for letter in word if letter not in string.punctuation) for word in words if word]
print(words)

Option 3 – Using `str.translate()`

import string
words = ["hell'o", "Hi,", "bye bye", "good bye", ""]
words = [word.translate(string.punctuation) for word in words if word]
print(words)

How to Normalize a List of Numbers in Python

Thu, 03 Nov 2022 00:05:00 +0000

If you need to normalize a list of numbers in Python, then you can do the following:

Option 1 – Using `Native Python`

list = [6,1,0,2,7,3,8,1,5]
print('Original List:',list)
xmin = min(list) 
xmax=max(list)
for i, x in enumerate(list):
    list[i] = (x-xmin) / (xmax-xmin)
print('Normalized List:',list)

Option 2 – Using `MinMaxScaler` from `sklearn`

import numpy as np
from sklearn import preprocessing
list = np.array([6,1,0,2,7,3,8,1,5]).reshape(-1,1)
print('Original List:',list)
scaler = preprocessing.MinMaxScaler()
normalizedlist=scaler.fit_transform(list)
print('Normalized List:',normalizedlist)

You can also specify the range of the MinMaxScaler().

How to Multiply a List by a Scalar in Python

Wed, 02 Nov 2022 00:05:00 +0000

If you need to multiply a list by a scalar in Python, then you can do one of the following:

Option 1 – Using `List Comprehensions`

li = [1,2,3,4]
multiple = 2.5
li = [x*multiple for x in li]
print(li)

Output: [2.5, 5.0, 7.5, 10.0]

Option 2 – Using `map()`

li = [1,2,3,4]
multiple = 2.5
def multiply(le):
    return le*multiple

li = list(map(multiply,li))
print(li)

Output: [2.5, 5.0, 7.5, 10.0]

Option 3 – Using `Lambda Functions`

li = [1,2,3,4]
multiple = 2.5
li = list(map(lambda x: x*multiple, li))
print(li)

Output: [2.5, 5.0, 7.5, 10.0]

How to Find the Index of the Minimum Element in a List in Python

Tue, 01 Nov 2022 00:05:00 +0000

If you need to find the index of the minimum element in a list, you can do one of the following:

Option 1 – Using `min()` and `index()`

lst = [8,6,9,-1,2,0]
m = min(lst)
print(lst.index(m))

Output: 3

Option 2 – Using `min()` and `for`

lst = [8,6,9,-1,2,0]
m = min(lst)
for i in range(len(lst)):
    if(lst[i]==m):
        print(i)
        break

Output: 3

Option 3 – Using `min()` and `enumerate()`

lst = [8,6,9,-1,2,0]
a,i = min((a,i) for (i,a) in enumerate(lst))
print(i)

Output: 3

How to Convert a Set to a String in Python

Mon, 31 Oct 2022 00:05:00 +0000

If you need to convert a set to a string in Python, then you can do one of the following:

Option 1 – Using `map()` and `join()`

str_new = ', '.join(list(map(str, se)))

You can confirm this worked as follows:

print(str_new)
print(type(str_new))

# '1, 2, 3'
# <class 'str'>

Option 2 – Using `repr()`

r_str = repr(se)

You can confirm this worked as follows:

print(r_str)
print(type(r_str))

# {1, 2, 3}
# <class 'str'>

How to Decrement a Loop in Python

Sun, 30 Oct 2022 00:05:00 +0000

If you need to decrement a loop in Python, then you can do the following:

How to Decrement a loop in Python using `-1`

The optional third argument you can pass to the range function is the order.

The default order is to count up / increment, while the -1 value, is to count down / decrement.

for i in range(3, 0, -1):
  print(i)

Output: 3 2 1

How to Decrement a loop in Python using `while`

You can also use a while loop and set the value to the upper bound, and then decrement while in the loop itself.

How to Create Zip Archive of Directory in Python

Sat, 29 Oct 2022 00:05:00 +0000

If you need to create a zip of a directory using Python, then you can do the following:

Create a Zip using `shutil` in Python

import os
import shutil

filename = "compressed_archive"
format = "zip"
directory = os.getcwd()

shutil.make_archive(filename, format, directory)

How to Remove the Last Character of a String in PHP

Fri, 28 Oct 2022 00:05:00 +0000

If you need to remove the last character of a string in PHP, then you can do the following:

Option 1 – Using `rtrim()`

Syntax: rtrim($string, $character)

$mystring = "This is a PHP program!";
echo("Before Removal: $mystring\n");
# Before Removal: This is a PHP program!

$newstring = rtrim($mystring, ". ");
echo("After Removal: $newstring");
# After Removal: This is a PHP program

Option 2 – Using `substr()`

Syntax: substr($string, $start, $length)

$mystring = "This is a PHP program!";
echo substr($mystring, 0, -1);
# This is a PHP program

How to Create Function with Multiple Returns in PHP

Thu, 27 Oct 2022 00:05:00 +0000

If you need to create a PHP function that returns multiple values, then you can do one of the following.

Option 1 – Returning an `array`

function returnArray() {
  return array("one", "two");
}

// call the function and print the response
var_dump(returnArray());

Option 2 – Returning a `conditional`

function returnConditional($x = true) {
  if ($x) return "one";
  else return "two";
}

// call the function with a value and print the response
var_dump(returnConditional(false));

Option 3 – Using `generator` to `yield` values

function multipleValues() {
  yield "one";
  yield "two";
}

$res = multipleValues();
foreach($res as $r) {
  echo $r; // first val=="one", second val=="two"
}

How to Download a File in NodeJS without any Third Party Libraries

Wed, 26 Oct 2022 00:05:00 +0000

If you need to download a file in NodeJS without using any third party libraries, then you can do the following.

The NodeJS ecosystem comes with a fs module, this is to denote the FileSystem built in library.

First declare your imports:

const http = require('https');
const fs = require('fs');

Now you can use the https module to download a file, and write it to a stream using fs.

const https = require("https");
const fs = require("fs");
 
const endpoint = "https://example/files/some_csv_file";
 
https.get(endpoint, (res) => {
  const file_name = "the_csv.csv";
  const writeStream = fs.createWriteStream(file_name);
});

How to Execute a Shell Script in NodeJS

Tue, 25 Oct 2022 00:05:00 +0000

If you need to execute a shell script in NodeJS, then you can use the exec keyword.

Syntax: exec(command [, options] [, callback]

const shell = require('shelljs')
shell.exec("npm --version")

How to Print Multiple Arguments in Python

Mon, 24 Oct 2022 00:05:00 +0000

If you need to print out multiple arguments using Python, then you can do one of the following:

Option 1 – Using `print`

print("Something", "Else", "Please")

Output: Something Else Please

Option 2 – Using `String Formatting`

print("Something {} {}".format("Else", "Please"))

Output: Something Else Please

Or with explicit ordering:

print("Something {1} {0}".format("Else", "Please"))

Output: Something Please Else

Option 3 – Using `F-String Formatting`

one = "Something"
two = "Else"
three = "Please"

print(f"{one} {two} {three}")

Output: Something Else Please

How to Delete all Resources Except One in Terraform

Sun, 23 Oct 2022 00:05:00 +0000

If you need to delete all resources created by Terraform, except for a single, specific one, then you can do the following:

Step 1 – Get the current `state list`

terraform state list

Step 2 – Remove the exception resource

Remove the specific resource that you don’t want Terraform to track anymore.

terraform state rm <resource_to_be_removed>

Step 3 – Destroy the resources

terraform destroy

How to Copy Files between Two Nodes using Ansible

Sat, 22 Oct 2022 00:05:00 +0000

If you need to copy files between two (2) nodes, using Ansible, then you can do the following:

This solution uses the synchronize module, specifically using the delegate_to:source-server keywords.

- hosts: serverB
  tasks:    
   - name: Copy Remote-To-Remote (from serverA to serverB)
     synchronize: src=https://andrewodendaal.com/copy/from_serverA dest=/copy/to_serverB
     delegate_to: serverA

How to Delete Files and Folders in a Directory using Ansible

Fri, 21 Oct 2022 00:05:00 +0000

If you need to delete files and folders in a directory using Ansible, then you can do the following:

- name: Delete content & entire directory
  file:
    state: absent
    path: /some/directory/path/

How to Copy Multiple Files with Ansible

Thu, 20 Oct 2022 00:05:00 +0000

If you need to copy multiple files using Ansible, then you can do the following:

How to Copy Multiple Files with Ansible

Look into using the with_fileglob loop as follows:

- copy:
    src: "{{ item }}"
    dest: /etc/fooapp/
    owner: root
    mode: 600
  with_fileglob:
    - /playbooks/files/fooapp/*

If you would like to do it as a task, then this could help:

- name: Your copy task
  copy: src={{ item.src }} dest={{ item.dest }}
  with_items:
    - { src: 'another_file', dest: '/etc/somewhere' }
    - { src: 'dynamic', dest: '{{ var_path }}' }
  # repeat for additional files

How to Write Multiline Shell Scripts in Ansible

Wed, 19 Oct 2022 00:05:00 +0000

If you need to write a shell script in Ansible, you probably have something like this:

- name: iterate user groups
  shell: groupmod -o -g {{ item['guid'] }} {{ item['username'] }}
  with_items: "{{ users }}"

But how do you write multiline shell scripts with this format?

How to write Multiline shell scripts

- name: iterate user groups
  shell: |
    groupmod -o -g {{ item['guid'] }} {{ item['username'] }} 
    do_some_stuff_here
    and_some_other_stuff
  with_items: "{{ users }}"

Just note that Ansible can do some strange things with manipulations of arguments, so you may want to follow something like this:

How to Pass Variables to Ansible Playbook CLI

Tue, 18 Oct 2022 00:05:00 +0000

If you need to pass a variable to Ansible playbook, using the command line, then you can do the following:

Option 1 – Specifying command line arguments

ansible-playbook release.yml --extra-vars "version=1.23.45 other_variable=foo"

N.B. --extra-vars specified variables will override any variables with the same name defined inside the playbook.

You can also read up on Passing Variables On The Command Line (Wayback Machine link to maintain versioning)

How to Create a Directory using Ansible

Mon, 17 Oct 2022 00:05:00 +0000

If you need to create a directory using Ansible, then you can do the following:

Create a Directory in Ansible

You will need the file module, then to create a directory you simply specify the option state=directory:

- name: Creates a directory
  file:
    path: /src/www
    state: directory

Note that with state=directory, all the immediate subdirectories will be created if they don’t already exist.

Extending the `file` module

- name: Creates a directory
  file:
    path: /src/www
    state: directory
    owner: www-data
    group: www-data
    mode: 0775

Create the Directories Recursively

- name: Creates directory
  file:
    path: /src/www
    state: directory
    owner: www-data
    group: www-data
    mode: 0775
    recurse: yes

This is similar to the recursive argument used with mkdir -p

How to Disable Screensaver on Mac using the CLI

Sun, 16 Oct 2022 00:05:00 +0000

If you want to disable the Screensaver on your Mac, by using the Command Line Interface (CLI), then you can do the following:

Step 1 – See what is currently set

defaults read com.apple.screensaver

Step 2 – Set the `idleTime`

defaults -currentHost write com.apple.screensaver idleTime 0

Step 3 – (Optional) – Undo the change

defaults -currentHost delete com.apple.screensaver idleTime

How to Remove Old and Unused Docker Images

Sat, 15 Oct 2022 00:05:00 +0000

If you need to remove any old and unused Docker images, then you can do the following:

How to Remove Old and Unused Docker Images

Firstly you need to see all the images:

docker images

You can also use ls to see the Docker Images:

docker image ls

How to Remove a Single Docker Image

The docker rmi command will remove a single Docker image as follows:

docker rmi <image_id>

You can also use the Docker image names as follows:

How to Convert Milliseconds to Date in Javascript

Fri, 14 Oct 2022 00:05:00 +0000

If you need to convert Milliseconds to Date in Javascript, then you can do the following:

How to Convert Milliseconds to Date in Javascript

let date = new Date(milliseconds);
date.toString();

Common Date Conversions From Milliseconds in Javascript

let originalDate = new Date(milliseconds);

// output: "D/MM/YYYY, H:MM:SS PM/AM"
originalDate.toLocaleString();

//output: "D/MM/YYYY"
originalDate.toLocaleDateString();

// output: "Day Month DD YYYY"
originalDate.toDateString();

// output: "HH:MM:SS GMT+0530"
originalDate.toTimeString();

// output: "Day Month DD YYYY HH:MM:SS GMT+0500"
originalDate.toString();

// output: "H:MM:SS AM/PM"
originalDate.toLocaleTimeString();

How to Convert String to Title Case in Javascript

Thu, 13 Oct 2022 00:05:00 +0000

If you need to convert a String to Title Case in Javascript, then you can do one of the following:

Option 1 – Using a `for` loop

function titleCase(str) {
  str = str.toLowerCase().split(' ');
  for (var i = 0; i < str.length; i++)
    str[i] = str[i].charAt(0).toUpperCase() + str[i].slice(1); 
  return str.join(' ');
}

console.log(titleCase("this is an example of some text!"));

Output: This Is An Example Of Some Text!

Option 2 – Using `map()`

function titleCase(str) {
  return str.toLowerCase().split(' ').map(function(word) {
    return (word.charAt(0).toUpperCase() + word.slice(1));
  }).join(' ');
}

console.log(titleCase("this is an example of some text!"));

Output: This Is An Example Of Some Text!

How to Compile Multiple Java Files from a Single Command in Java

Wed, 12 Oct 2022 00:05:00 +0000

If you need to compile multiple Java files using a single command, then you can do the following.

First, it’s good to learn how to compile a Java file.

How to Compile a Java File

Let’s take the following Java code:

class HelloWorld {
  public static void main(String[] args) {
    System.out.println("Hello World");
  }
}

To compile this, we simply do the following:

javac HelloWorld.java

Then when we need to run it, we do:

How to Convert JSON to a Java Object

Tue, 11 Oct 2022 00:05:00 +0000

If you need to convert JSON to a Java Object, then you can do one of the following:

Option 1 – Using `Gson`

import com.google.gson.Gson;

public class SimpleTesting {
    public static void main(String[] args) throws InterruptedException {
        String json = """
            {
                "firstName" : "Jane",
                "lastName" : "Doe",
                "dateOfBirth" : "1973-04-29",
                "address" : "81 Hype",
                "city" : "New York",
                "contact" : "0123456789"
            }
            """;
        Student data = new Gson().fromJson(json, Student.class);

        System.out.println(data.getFirstName());
        System.out.println(data.getLastName());
        System.out.println(data.getCity());
    }
}

class Student {
    private String firstName;
    private String lastName;
    private String dateOfBirth;
    private String address;
    private String city;
    private String contact;

    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getDateOfBirth() {
        return dateOfBirth;
    }
    public void setDateOfBirth(String dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getContact() {
        return contact;
    }
    public void setContact(String contact) {
        this.contact = contact;
    }
}

Option 2 – Using `Jackson`

import java.io.File;
import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class SimpleTesting {
    public static void main(String[] args) throws InterruptedException {
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);
        try {
            Student student = mapper.readValue(new File("json-file.json"), Student.class);

            System.out.println("First Name: "+student.getFirstName());
            System.out.println("Last Name: "+student.getLastName());
            System.out.println("City: "+student.getCity());
            System.out.println("Address: "+student.getAddress());
            System.out.println("Contact: "+student.getContact());
            System.out.println("Date of Birth: "+student.getDateOfBirth());
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}

class Student {
    private String firstName;
    private String lastName;
    private String dateOfBirth;
    private String address;
    private String city;
    private String contact;

    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getDateOfBirth() {
        return dateOfBirth;
    }
    public void setDateOfBirth(String dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getContact() {
        return contact;
    }
    public void setContact(String contact) {
        this.contact = contact;
    }
}

How to Calculate Powers of Integers in Java

Mon, 10 Oct 2022 00:05:00 +0000

If you need to calculate the powers of Integers in Java, then you can do one of the following:

Option 1 – Using `for` loops

public class Power {
    public static void main(String args[]){
        int number = 5;
        int power = 3;
        int result = calculatePower(number,power);
        System.out.println(number+"^"+power+"="+result);
    }
    static int calculatePower(int num, int power){
        int answer = 1;
        if (num > 0 && power==0){
            return answer;
        } else if(num == 0 && power>=1){
            return 0;
        } else{
            for(int i = 1; i<= power; i++)
                answer = answer*num;
            return answer;
        }
    }
}

Option 2 – Using Recursion

public class Power {
    public static void main(String args[]){
        int number = 3;
        int power = 3;
        int result = CalculatePower(number,power);
        System.out.println(number+"^"+power+"="+result);
    }
    static int CalculatePower (int num, int pow){
        if (pow == 0)
            return 1;
        else
            return num * CalculatePower(num, pow - 1);
    }
}

Option 3 – Using `Math.pow()`

import java.lang.Math;
public class Power {
    public static void main(String args[]){
        int number = 6;
        int power = 3;
        double result = CalculatePower(number,power);
        System.out.println(number+"^"+power+"="+result);
    }
    static double CalculatePower (int num, int pow){
        return Math.pow(num,pow);
    }
}

How to Get Today’s Date in Java

Sun, 09 Oct 2022 00:05:00 +0000

If you need to get today’s date in Java, then you can do one of the following:

Option 1 – Using `LocalDate`

import java.time.LocalDate;

public class GetTodayDate {
    public static void main(String[] args) {
        LocalDate todaysDate = LocalDate.now();
        System.out.println(todaysDate);
    }
}

Option 2 – Using `Calendar` and `SimpleDateFormat`

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class GetTodayDate {
    public static void main(String[] args) {
        SimpleDateFormat dtf = new SimpleDateFormat("yyyy/MM/dd");
        Calendar calendar = Calendar.getInstance();

        Date dateObj = calendar.getTime();
        String formattedDate = dtf.format(dateObj);
        System.out.println(formattedDate);
    }
}

Option 3 – Using `java.sql.Date`

import java.sql.Date;

public class GetTodayDate {
    public static void main(String[] args) {
        long miliseconds = System.currentTimeMillis();
        Date date = new Date(miliseconds);
        System.out.println(date);
    }
}

How to Copy Files from Docker Container to Host

Sat, 08 Oct 2022 00:05:00 +0000

If you need to copy files from a Docker Container to the Host, then you can do one of the following:

Option 1 – Using `docker cp`

Syntax:

docker cp [OPTIONS] CONTAINER: SRC_PATH DEST_PATH

Setup the container:

# pull the ubuntu image
docker pull ubuntu

# run the container locally
docker run -it -d ubuntu

# connect to the container
docker exec -it abcde123456 /bin/bash

Create a file from the container:

cd usr
cd share
touch some_file.txt
ls

Copy the file from the container to the host:

How to Get the IP Address of a Docker Container

Fri, 07 Oct 2022 00:05:00 +0000

If you need to get the IP Address of a Docker Container, then you can do the following:

Option 1 – Connect to the Bridge Network

Find out the network setup:

docker network ls

Create a docker container and assign it to the bridge network:

docker run -dt <nginx>

Get the information about the container:

docker ps

Inspect the network:

docker network inspect bridge

Now you can see the container IP Address.

Option 2 – Use `docker inspect`

Use the container id to get detailed information:

How to Convert Time to String in Golang

Thu, 06 Oct 2022 00:05:00 +0000

If you need to convert Time to a String in Go, then you can do one of the following:

Option 1 – Using `time.Now`

package main

import (
    "fmt"
    "time"
)

func main() {
    currentTime := time.Now()
    fmt.Println("Time: ", currentTime.String())
}

Option 2 – Using `time.Time.String()`

package main

import (
    "fmt"
    "time"
)

func main() {
    Time := time.Date(2022, 03, 28, 03, 50, 16, 0, time.UTC)
    t := Time.String()
    fmt.Printf("Time without the nano seconds: %v\n", t)
}

How to Perform a Deep Copy in Golang

Wed, 05 Oct 2022 00:05:00 +0000

To perform a Deep Copy in Go, you can use a struct type as follows:

Deep Copying using a `struct` in Go

package main

import (
    "fmt"
)

type Dog struct {
    age     int
    name    string
    friends []string
}

func main() {
    john := Dog{1, "Harry", []string{"Steve", "Matt", "Sarah"}}
    jack := john

    jack.friends = make([]string, len(john.friends))
    copy(jack.friends, harry.friends)

    jack.friends = append(jay.friends, "Fred")

    fmt.Println(john)
    fmt.Println(jack)
}

How to Return Lambda Functions in Golang

Tue, 04 Oct 2022 00:05:00 +0000

Go doesn’t typically have Lambda Expressions, but synonymous to Lambdas, or Closures if Anonymous Functions for Go.

How to return a value from an Anonymous Function in Go

package main

import "fmt"

func main() {
    var sum = func(n1, n2 int) int {
        sum := n1 + n2
        return sum
    }
    result := sum(5, 3)
    fmt.Println("Sum is:", result)
}

How to return an Area from an Anonymous Function in Go

package main

import "fmt"

var (
    area = func(l int, b int) int {
        return l * b
    }
)
func main() {
    fmt.Println(area(10, 10))
}

How to Create an Empty Slice in Golang

Mon, 03 Oct 2022 00:05:00 +0000

If you would like to create an empty slice in Go, then you can do the following:

Option 1 – Initialize an Empty Slice in Go

package main

import "fmt"

func main() {
    b := []string{}
    fmt.Println(b == nil)
}

Option 2 – Using `make()`

package main

import "fmt"

func main() {
    c := make([]string, 0)
    fmt.Println(c == nil)
}

How to Parallelize a for Loop in Python

Sun, 02 Oct 2022 00:05:00 +0000

If you need to run a for loop in parallel, then you can do one of the following:

Option 1 – Using `multiprocessing`

import multiprocessing

def sumall(value):
    return sum(range(1, value + 1))

pool_obj = multiprocessing.Pool()

answer = pool_obj.map(sumall,range(0,5))
print(answer)

Option 2 – Using `joblib` module

from joblib import Parallel, delayed
import math

def sqrt_func(i, j):
    time.sleep(1)
    return math.sqrt(i**j)

Parallel(n_jobs=2)(delayed(sqrt_func)(i, j) for i in range(5) for j in range(2))

Option 3 – Using `asyncio`

import asyncio
import time

def background(f):
    def wrapped(*args, **kwargs):
        return asyncio.get_event_loop().run_in_executor(None, f, *args, **kwargs)
    return wrapped

@background
def your_function(argument):
    time.sleep(2)
    print('function finished for '+str(argument))

for i in range(10):
    your_function(i)

print('loop finished')

How to Reverse an Integer in Python

Sat, 01 Oct 2022 00:05:00 +0000

If you need to reverse an integer using Python, then you can do the following:

Option 1 – Mathematical Palindrome Check

original_number = 123454321
copy_number = original_number
reversed_number = 0

while original_number > 0:
    remainder = original_number % 10
    reversed_number = reversed_number * 10 + remainder
    original_number = original_number // 10

if copy_number == reversed_number:
    print(copy_number, 'is a palindrome number')
else:
    print(copy_number, 'is not a palindrome number')

Option 2 – String Reversal Number Palindrome

number = 123454321

if number == int(str(number)[::-1]):
    print(number, 'is palindrome.')
else:
    print(number, 'is not palindrome.')

Option 3 – List Reversal Number Palindrome

original_number = 123454321
lst_number = list(str(original_number))
lst_number.reverse()
reversed_number = ''.join(lst_number)

if (original_number == int(reversed_number)):
    print(original_number, 'is palindrome.')
else:
    print(original_number, 'is not palindrome.')

Terraform for AWS: Cloud-Native Infrastructure

Sat, 01 Oct 2022 00:00:00 +0000

AWS and Terraform are a powerful combination, but AWS’s complexity means there are specific patterns, gotchas, and best practices that aren’t obvious from general Terraform knowledge. This guide bridges that gap, covering the AWS-specific techniques that separate basic resource creation from production-ready, well-architected infrastructure.

From VPC design patterns to multi-account strategies, this guide covers the real-world challenges you’ll face when managing AWS infrastructure at scale with Terraform.

AWS Provider Setup

The AWS provider is Terraform’s gateway to Amazon Web Services, but configuring it properly for production use involves more than just setting a region. Authentication strategies, provider aliases for multi-region deployments, and proper credential management are essential for building reliable, secure infrastructure automation.

How to Save a Python Dictionary to a File in Python

Fri, 30 Sep 2022 00:05:00 +0000

If you need to save a Python Dictionary object type to a file using Python, then you can do one of the following:

Option 1 – Using `pickle` module

import pickle

my_dict = { 'Bob': 31, 'Jane': 50, 'Harry': 13, 'Steve': 23}

with open("dictionaryFile.pkl", "wb") as tf:
    pickle.dump(my_dict,tf)

Then you can load the pickle file back as follows:

import pickle

with open("dictionaryFile.pkl", "wb") as tf:
    new_dict = pickle.load(tf)

print(new_dict)

Option 2 – Using `numpy`

import numpy as np

my_dict = { 'Bob': 31, 'Jane': 50, 'Harry': 13, 'Steve': 23}
np.save('dictionaryFile.npy', my_dict)

Then you can load the file back as follows:

Terraform Fundamentals: Infrastructure as Code

Fri, 30 Sep 2022 00:00:00 +0000

Infrastructure as Code isn’t just a buzzword—it’s the difference between spending your weekend manually clicking through cloud consoles and having reproducible, version-controlled infrastructure that deploys consistently every time. Terraform has become the de facto standard for managing cloud resources, but mastering it requires understanding not just the syntax, but the patterns and practices that separate toy projects from production-ready infrastructure.

This guide takes you from writing your first Terraform configuration to architecting complex, multi-environment infrastructure with proper state management, security, and team collaboration patterns.

How to Move Files From One Directory to Another Using Python

Thu, 29 Sep 2022 00:05:00 +0000

If you need to move files from one directory to another directory, using Python, then you can do one of the following:

Option 1 – Using `shutil.move()`

import shutil
import os
 
file_source = 'source/directory'
file_destination = 'destination/directory'
 
get_files = os.listdir(file_source)
 
for file in get_files:
    shutil.move(file_source + file, file_destination)

Option 2 – Using `os.replace()`

import os
 
file_source = 'source/directory'
file_destination = 'destination/directory'
 
get_files = os.listdir(file_source)
 
for file in get_files:
    os.replace(file_source + file, file_destination + file)

Option 3 – Using `pathlib`

from pathlib import Path
import shutil
import os

file_source ='source/directory'
file_destination ='destination/directory'

for file in Path(file_source).glob('some_file.txt'):
    shutil.move(os.path.join(file_source,file), file_destination)

How to Get the Number of Lines in a File in Python

Wed, 28 Sep 2022 00:05:00 +0000

If you need to get the number of lines in a file, or the line count total from a file, using Python, then you can use one of the following options:

Option 1 – Using `open()` and `sum()`

with open('directory/file.txt') as myfile:
    total_lines = sum(1 for line in myfile)

print(total_lines)

Option 2 – Using `mmap`

import mmap

with open('directory/file.txt', "r+") as myfile:
    mm = mmap.mmap(myfile.fileno(), 0)
    total_lines = 0

    while mm.readline():
        total_lines += 1

print(total_lines)

Option 3 – Using `file.read()`

lines = 0
size = 1024 * 1024

with open(r'directory/file.txt', "r+") as myfile:
    read_file = myfile.read

    buffer = read_file(size)
    
    while buffer:
        lines += buffer.count('\n')
        buffer = read_file(size)

if (lines != 0):
    lines += 1

print(lines)

How to Read Specific Lines From a File in Python

Tue, 27 Sep 2022 00:05:00 +0000

If you need to read a specific line from a file using Python, then you can use one of the following options:

Option 1 – Using `fileobject.readlines()`

If you need to read line 10:

with open("file.txt") as f:
    data = f.readlines()[10]
print(data)

If you need to read lines 10, to 20:

with open("file.txt") as f:
    data = f.readlines()[10:20]
print(data)

Option 2 – Using `for` in `fileobject`

lines =[10, 20]
data = []
i = 0

with open("file.txt", "r+") as f:
    for line in f:
        if i in lines:
            data.append(line.strip)
            
        i = i + 1

print(data)

Option 3 – Using `linecache` module

import linecache
data = linecache.getline('file.txt', 10).strip()

Option 4 – Using `enumerate`

with open("file.txt") as f:
    for i, line in enumerate(f):
        pass  # process line i

How to Get All Files in a Directory in Python

Mon, 26 Sep 2022 00:05:00 +0000

If you need to get all the files in a directory using Python, then you can do the following:

Option 1 – Using `os.listdir()`

import os

dirPath = r"/your/directory/path/"
result = [f for f in os.listdir(dirPath) if os.path.isfile(os.path.join(dirPath, f))]

print(result)

Option 2 – Using `os.walk()`

import os

dirPath = r"/your/directory/path/"
result = next(os.walk(dirPath))[2]

print(result)

Option 3 – Using `glob.glob()`

import glob

dirPathPattern = r"/your/directory/path/*.*"
result = glog.glob(dirPathPattern)

print(result)

[Solved] dial tcp: lookup proxy.golang.org: i/o timeout

Sun, 25 Sep 2022 00:05:00 +0000

If you get a timeout when trying to install go dependencies, the error may look something like this:

$ go get github.com/aws/aws-sdk-go/aws

go: module github.com/aws/aws-sdk-go/aws: Get "https://proxy.golang.org/github.com/aws/aws-sdk-go/aws/@v/list": dial tcp: lookup proxy.golang.org: i/o timeout

How to Solve the Timeout Issue when installing Go Deps

export GOPROXY=direct

Then re-run your go get command.

How to Check Operating System in Python

Sat, 24 Sep 2022 00:05:00 +0000

If you need to check the Operating System information from Python, then you can do one of the following:

Option 1 – Using the `platform` module

import platform
my_os = platform.system()
print("Operating System is: ",my_os)

Option 2 – Using the `sys` module

import sys
my_os=sys.platform
print("Operating System is: ",my_os)

How to Convert Hex to Byte in Python

Fri, 23 Sep 2022 00:05:00 +0000

If you need to convert Hex to Byte in Python, then you can do one of the following:

Option 1 – Using `binascii`

import binascii
str_val = 'This is a test'.encode('utf-8')
hex_val = binascii.hexlify(str_val).decode('utf-8')

print(hex_val)

Option 2 – Using `bytes.fromhex()`

hex_val = 'This is a test'

print(bytes.fromhex(hex_val))

Option 3 – Using `unhexlify`

import binascii
from binascii import unhexlify

str_val = 'This is a test'.encode('utf-8')
hex_val = binascii.hexlify(str_val).decode('utf-8')

print('String value: ', str_val.decode('utf-8'))
print('Hexadecimal: ', hex_val)
print('Byte value: ', unhexlify(hex_val))

[Solved] fatal: Could not read from remote repository with Git

Thu, 22 Sep 2022 00:05:00 +0000

If you receive the following error when trying to clone a Git repository:

fatal: Could not read from remote repository.

The full message may look something like this:

$ git clone git@ssh.abc.xyz:org/repo.git
Cloning into 'repo'...
Bad owner or permissions on /Users/ao/.ssh/config
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

How to solve this error

ssh-add ~/.ssh/id_rsa

where id_rsa is a ssh key associated with the repo.

How to Install Homebrew on a Mac

Wed, 21 Sep 2022 00:05:00 +0000

Prerequisites

You should have some familiarity with the Mac Terminal application since you’ll need to use it to install Homebrew. The Terminal application is located in the Utilities folder in the Applications folder.
Dependencies. You need to install one other piece of software before you can install Homebew:
- Xcode. Install Apple’s Xcode development software: Xcode in the Apple App Store.

Installation Overview

Installing Homebrew is straightforward as long as you understand the Mac Terminal. The Homebrew installation process guides through each step.

How to create an AWS EC2 instance in CloudFormation

Tue, 20 Sep 2022 00:05:00 +0000

Create an EC2 Instance in CloudFormation

If you need to create an EC2 instance in CloudFormation, then you can do the following:

AWSTemplateFormatVersion: "2010-09-09"
Resources:
  WebInstance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.nano
      ImageId: ami-80861296
      KeyName: my-key
      SecurityGroupIds:
        - sg-abc01234
      SubnetId: subnet-abc01234

You can set the Instance Name as follows:

AWSTemplateFormatVersion: "2010-09-09"
Resources:
  WebInstance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.nano
      ImageId: ami-80861296
      KeyName: my-key
      SecurityGroupIds:
        - sg-abc01234
      SubnetId: subnet-abc01234
      Tags:
        -
          Key: Name
          Value: webserver

You can Enable Monitoring as follows:

How to Run Commands on an AWS ECS Cluster Task or Container

Mon, 19 Sep 2022 00:05:00 +0000

If you need to run a command, or set of commands on an AWS ECS cluster container, then you can do the following:

aws ecs execute-command --cluster ${ClusterName} --task ${TASK_ARN} --container nginx --command "/bin/sh" --interactive

Understanding the Network Modes in AWS ECS

Sun, 18 Sep 2022 00:05:00 +0000

If using the EC2 launch type, the allowable network mode depends on the underlying EC2 instance’s operating system. If Linux, awsvpc, bridge, host and none mode can be used. If Windows, only the NAT mode is allowed.

If using the Fargate launch type, the ‘awsvpc’ is the only network mode supported.

Amazon ECS task networking

The networking behavior of Amazon ECS tasks hosted on Amazon EC2 instances is dependent on the network mode defined in the task definition. The following are the available network modes. Amazon ECS recommends using the awsvpc network mode unless you have a specific need to use a different network mode.

How to Enable ContainerInsights on AWS ECS from the AWS CLI

Sat, 17 Sep 2022 00:05:00 +0000

If you need to enable Container Insights for an ECS cluster, by using the AWS CLI, then you can do the following:

aws ecs update-cluster-settings
    --cluster <cluster-name>  
    --settings name=containerInsights,value=enabled 
    --region <aws_region>

AppMesh and ECS with Imported ACM certificates on Envoy Sidecar through EFS

Fri, 16 Sep 2022 00:05:00 +0000

Summary

This guide showcases the ability to use imported certificates from a third party provider (e.g. Venafi) in ACM, mount them in EFS and use them as trusted sources on Envoy sidecars with applications running in ECS. AppMesh is used as a passthrough with TLS termination occurring on the application container layer.

Prerequisites and limitations

Prerequisites

A certificate that contains the chain of domains required for the fronted service and micro-services needed.

How to Increase the disk size on a Cloud9 instance

Thu, 15 Sep 2022 00:05:00 +0000

If you need to increase the disk size of a Cloud9 instance, you can run the following script directly from the terminal in Cloud9:

pip3 install --user --upgrade boto3
export instance_id=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
python3 -c "import boto3
import os
from botocore.exceptions import ClientError 
ec2 = boto3.client('ec2')
volume_info = ec2.describe_volumes(
    Filters=[
        {
            'Name': 'attachment.instance-id',
            'Values': [
                os.getenv('instance_id')
            ]
        }
    ]
)
volume_id = volume_info['Volumes'][0]['VolumeId']
try:
    resize = ec2.modify_volume(    
            VolumeId=volume_id,    
            Size=30
    )
    print(resize)
except ClientError as e:
    if e.response['Error']['Code'] == 'InvalidParameterValue':
        print('ERROR MESSAGE: {}'.format(e))"
if [ $? -eq 0 ]; then
    sudo reboot
fi

How to Get the Instance Profile attached to an AWS EC2

Wed, 14 Sep 2022 00:05:00 +0000

If you need to get the IAM Role information from the attached EC2 role directly, you can do the following:

IAM_ROLE=$(curl -s 169.254.169.254/latest/meta-data/iam/info | \
  jq -r '.InstanceProfileArn' | cut -d'/' -f2)

How to Create an AWS ECR Repository in AWS CLI

Tue, 13 Sep 2022 00:05:00 +0000

If you need to create an Elastic Container Registry (ECR) Repository from the AWS CLI, you can do the following:

aws ecr create-repository \
--repository-name <repo-name> \
--image-scanning-configuration scanOnPush=true \
--region ${AWS_REGION}

How to Scale Out an AWS ECS Service

Mon, 12 Sep 2022 00:05:00 +0000

When you create the Amazon ECS service, it includes three Amazon ECS task replicas. You can see this by using the describe-services command, which returns three. Use the update-service command to scale the service to five tasks. Re-run the describe-services command to see the updated five.

Step 1 – Query the desired count

aws ecs describe-services \
--cluster fargate-getting-started \
--services nginx-service \
--query 'services[0].desiredCount'

Output: 3

Step 2 – Set the new desired count

aws ecs update-service \
--cluster fargate-getting-started \
--service nginx-service \
--desired-count 5

This will now update the service to have a desired count of 5.

How to Retrieve AWS ECS Cluster Information

Sun, 11 Sep 2022 00:05:00 +0000

For more information about the Amazon ECS cluster, run the following command. You will find the number of running tasks, capacity providers, and more.

aws ecs describe-clusters --cluster <your-fargate-cluster>

Sample output:

{
    "clusters": [
        {
            "clusterArn": "arn:aws:ecs:us-east-2:123456789012:cluster/<your-fargate-cluster>",
            "clusterName": "fargate-getting-started",
            "status": "ACTIVE",
            "registeredContainerInstancesCount": 0,
            "runningTasksCount": 3,
            "pendingTasksCount": 0,
            "activeServicesCount": 1,
            "statistics": [],
            "tags": [],
            "settings": [],
            "capacityProviders": [
                "FARGATE",
                "FARGATE_SPOT"
            ],
            "defaultCapacityProviderStrategy": []
        }
    ],
    "failures": []
}

Types of communication in Amazon EKS

Sat, 10 Sep 2022 00:05:00 +0000

There are multiple types of communication in Amazon EKS environments. Lines of communication include the following:

Interpod communication between containers
Communication between pods on the same node or pods on different nodes
Ingress connections from outside the cluster

In some cases, the default Kubernetes methods are used. In other cases, specifically inter-node communication and ingress methods specific to Amazon EKS are used.

Intrapod communication

Containers in a pod share a Linux namespace and can communicate with each other using localhost. In Kubernetes networking, the IP address with which a container identifies is the same IP address for all entities in the network. All containers can communicate with all other containers in a pod without NAT.

[Solved] Read timeout on endpoint URL: “https://lambda.[region].amazonaws.com/2015-03-31/functions/[function-name]/invocations”

Fri, 09 Sep 2022 00:05:00 +0000

If you get the following error:

Read timeout on endpoint URL: "https://lambda.<region>.amazonaws.com/2015-03-31/functions/<function-name>/invocations"

Then you are probably trying to use the aws cli to invoke an AWS Lambda function and it is timing out.

Other than making sure to set the Lambda execution time to something much higher than it is, you also need to make sure to specify the aws cli --cli-read-timeout argument to something that will cover the execution time.

How to Remove a Passphrase from Certificate Key

Thu, 08 Sep 2022 00:05:00 +0000

If you have a Certificate Key that includes a Passphrase and you need to remove it, potentially to use it with AWS App Mesh, then you can do the following:

How to Remove a Passphrase using OpenSSL

Locate the Private Key
Run the following command:
open ssl rsa -in <original.key> -out <new.key>
Enter the original passphrase for the existing key
The output file <new.key> will now be unencrypted

How to Verify if the Passphrase has been removed

Open the file in a text editor and check the headers.

How to get Python logger to Print to std out

Wed, 07 Sep 2022 00:05:00 +0000

If you use Python’s logger as follows:

import logging
logger = logging.getLogger()
logger.setLevel(logging.DEBUG) # or logging.INFO

Perhaps you want to get it to print to Standard Output (stdout), then you can do the following:

Setup Logger to print to Standard Output

import logging

logger = logging.getLogger()
# logger.setLevel(logging.INFO)
logger.setLevel(logging.DEBUG)

handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
logger.addHandler(handler)

This way you can now log straight to the console as well:

How to Convert a String to an Integer in C

Tue, 06 Sep 2022 00:05:00 +0000

If you need to convert a String to an Integer in C, then you can do one of the following:

Option 1 – Use `atoi()`

int atoi(const char *str);

You can do something like this:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main (void) {
    int value;
    char str[20];
    strcpy(str,"123");
    value = atoi(str);
    printf("String value = %s, Int value = %d\n", str, value);

    return(0);
}

Option 2 – Use `strtol()`

long int strtol(const char *string, char **laststr,int basenumber);

How to Convert an Integer to a String in C

Mon, 05 Sep 2022 00:05:00 +0000

If you need to convert an Integer to a String in C, then you can do one of the following:

Option 1 – Use `sprintf()`

int sprintf(char *str, const char *format, [arg1, arg2, ... ]);

You can do something like this:

#include <stdio.h>

int main(void) {
	int number;
	char text[20]; 

	printf("Enter a number: ");
	scanf("%d", &number);

	sprintf(text, "%d", number);

	printf("\nYou have entered: %s", text);

	return 0;
}

Option 2 – Use `itoa()`

char* itoa(int num, char * buffer, int base)

How to append to an Array in Elasticsearch using elasticsearch-py

Sun, 04 Sep 2022 00:05:00 +0000

If you are using the Official ElasticSearch Python library (Docs), and you want to create an index:

doc = {
    "something": "123a",
    "somethingelse": "456b",
    "timestamp": datetime.now(),
    "history": []
}
es.index(index="someindex", doc_type="somedoctype", id="someid", body=doc)

You can append items to the history each time, instead of overriding them, like this:

es.update(index="someindex", doc_type="somedoctype", id="someid",
    body={
        "script" : {
            "source": "ctx._source.history.addAll(params.history)",
            "lang": "painless",
            "params" : {
                "history" : ["item1","item2"]
            }
        }
    })

This uses scripted updates in Elasticsearch, for appending to an array.

How to Copy Text to the Clipboard in Python

Sat, 03 Sep 2022 00:05:00 +0000

If you need to Copy Text to the Clipboard using your Python application code, then you can do the following:

Option 1 – Using `pyperclip`

First install the pyperclip package, using pip:

pip install pyperclip

Now you can run the following code:

import pyperclip as pc

a1 = "This text will now be in your clipboard"
pc.copy(a1)
a2 = pc.paste()

print(a2)
print(type(a2))

Option 2 – Using `pyperclip3`

This version is similar to the first option above, except it copies all the data into bytes.

How to Read a PDF file in Python

Fri, 02 Sep 2022 00:05:00 +0000

If you need to read a PDF (Portable Document Format) file in your Python code, then you can do the following:

Option 1 – Using `PyPDF2`

from PyPDF2 import PDFFileReader
temp = open('your_document.pdf', 'rb')
PDF_read = PDFFileReader(temp)
first_page = PDF_read.getPage(0)
print(first_page.extractText())

Option 2 – Using `PDFplumber`

import PDFplumber
with PDFplumber.open("your_document.PDF") as temp:
  first_page = temp.pages[0]
  print(first_page.extract_text())

Option 3 – Using `textract`

import textract
PDF_read = textract.process('document_path.PDF', method='PDFminer')

How to Convert HEX to RBG in Python

Thu, 01 Sep 2022 00:05:00 +0000

If you need to convert HEX (Hexadecimal) to RGB (Red-Green-Blue) in your Python code, then you can do the following:

Option 1 – Using the `PIL` library

from PIL import ImageColor
hex = input('Enter HEX value: ')
ImageColor.getcolor(hex, "RGB")

Option 2 – Using a custom solution

hex = input('Enter HEX value: ').lstrip('#')
print('RGB value =', tuple(int(hex[i:i+2], 16) for i in (0, 2, 4)))

How to Refer to a Null Object in Python

Wed, 31 Aug 2022 00:05:00 +0000

If you need to refer to a Null Object in your Python code, then you can do the following.

It is important to note that Python does not have a Null type, instead Python refers to not set objects or variables as None.

We can use the is keyword to check if an object or variable has the type of None.

object_name = None
print(object_name is None)

object_name = ' some_value'
print(object_name is None)

How to Convert Bytearray to String in Python

Tue, 30 Aug 2022 00:05:00 +0000

If you need to convert a Bytearray to a String in Python, then you can do the following:

Option 1 – Using `bytes()`

b = bytearray("test", encoding="utf-8")
str1 = bytes(b)
print(str1)

Option 2 – Using `bytearray.decode()`

b = bytearray("test", encoding="utf-8")
str1 = b.decode()
print(str1)

How to get the Hostname in Python

Mon, 29 Aug 2022 00:05:00 +0000

If you need to get the Hostname in your Python application, then you can do the following:

Option 1 – Using `gethostname()`

import socket
print(socket.gethostname())

Option 2 – Using the `platform` module

import platform
print (platform.node())

Option 3 – Using `os.uname()`

import os
hname = os.uname()
print(hname)

How to get the IP Address in Python

Sun, 28 Aug 2022 00:05:00 +0000

If you need to get the IP Address in your Python application, then you can do the following:

Option 1 – Using `socket.gethostname()`

import socket
print(socket.gethostbyname(socket.gethostname()))

Option 2 – Using `socket.getsockname()`

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect(("8.8.8.8", 80))
print(s.getsockname()[0])

Option 3 – Using the `netifaces` module

from netifaces import interfaces, ifaddresses, AF_INET
for ifaceName in interfaces():
    addresses = [i['addr'] for i in ifaddresses(ifaceName).setdefault(AF_INET, [{'addr':'No IP addr'}] )]
    print(' '.join(addresses))

How to use SSH in your Python application

Sat, 27 Aug 2022 00:05:00 +0000

If you need to make an SSH connection and issues commands over SSH using your Python application, then you can do the following:

Option 1 – Using the `paramiko` library

ssh = paramiko.SSHClient()
ssh.connect(server, username=username, password=password)
ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command(cmd_to_execute)

Option 2 – Using the `subprocess` module

subprocess.check_output(['ssh', 'my_server', 'echo /*/'])

Option 3 – Using the `subprocess` module

subprocess.Popen("ssh {user}@{host} {cmd}".format(user=user, host=host, cmd='ls -l'), shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()

How to Pause a Program in Python

Fri, 26 Aug 2022 00:05:00 +0000

If you need to pause the execution of your Python program, then you can do the following:

Option 1 – Using `time.sleep()`

import time

time_duration = 3.5
time.sleep(time_duration)

Option 2 – Using `input()`

name = input("Please enter your name: ")
print("Name:", name)

Option 3 – Using `os.system("pause")`

import os

os.system("pause")

How to Convert String to Double in Python

Thu, 25 Aug 2022 00:05:00 +0000

If you need to convert a String to a Double in your Python code:

Option 1 – Convert String to Double using `float()`

string = '1234.5678'
myfloat = float(string)
print(myfloat)

Option 2 – Convert String to Double using `decimal.Decimal()`

from decimal import Decimal

string = '1234.5678'
myfloat = Decimal(string)
print(myfloat)

How to a Run Bash Command in Python

Wed, 24 Aug 2022 00:05:00 +0000

If you need to run a bash command in your Python code, then you can do the following:

Option 1 – Using `run()` from `subprocess` Module

from subprocess import PIPE

comp_process = subprocess.run("ls",stdout=PIPE, stderr=PIPE)
print(comp_process.stdout)

Option 2 – Using `Popen()` from `subprocess` Module

from subprocess import PIPE

process = subprocess.Popen("ls",stdout=PIPE, stderr=PIPE)
output, error = process.communicate()
print(output)
process.kill

How to Force Redeployment of AWS API Gateway using AWS CloudFormation

Tue, 23 Aug 2022 00:05:00 +0000

If you have an AWS API Gateway resource, and need it to force a redeployment using CloudFormation, then you can use the TIMESTAMP trick.

Example AWS CloudFormation Extract

template.yaml extract:

APIGatewayStage:
    Type: AWS::ApiGateway::Stage
    Properties:
      StageName: !Sub ${EnvironmentTagName}
      RestApiId: !Ref APIGateway
      DeploymentId: !Ref APIGatewayDeployment__TIMESTAMP__
      TracingEnabled: true
      MethodSettings:
          - DataTraceEnabled: true
            HttpMethod: "*"
            LoggingLevel: INFO
            ResourcePath: "/*"
            MetricsEnabled: true

  APIGatewayDeployment__TIMESTAMP__:
    Type: AWS::ApiGateway::Deployment
    Properties:
      RestApiId: !Ref APIGateway
      Description: !Sub ${EnvironmentTagName} Deployment __TIMESTAMP__

  APIGateway:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: !Ref "AWS::StackName"
      ...

As we can see, on line 15 above, we use the __TIMESTAMP__ string in the APIGatewayDeployment stage.

How to Deploy React App to S3 and CloudFront

Mon, 22 Aug 2022 00:05:00 +0000

If you would like to deploy a React App to AWS S3 and AWS CloudFront, then you can follow this guide.

The following solution creates a React App and deploys it to S3 and CloudFront using the client’s CLI.
It also chains commands so that a React build, S3 sync and CloudFront invalidation can occur with a single command.

Code available at GitHub

https://github.com/ao/deploy-react-to-s3-cloudfront

[Solved] export ‘Switch’ (imported as ‘Switch’) was not found in ‘react-router-dom’

Sun, 21 Aug 2022 00:05:00 +0000

In react-router-dom v6, Switch is replaced by routes Routes.

You need to update the import from:

import { Switch, Route } from "react-router-dom";

to:

import { Routes, Route } from 'react-router-dom';

You also need to update the Route declaration from:

<Route path="/" component={Home} />

to:

<Route path='/welcome' element={<Home/>} />

How to List all Files/Folders/Directories in Python

Sat, 20 Aug 2022 00:05:00 +0000

If you need to list all Files, Folders, or Directories in Python code, then you can use the listdirs method from the os package.

import os
print(os.listdir("/path/to/directory/")

How to Read a File in Python

Fri, 19 Aug 2022 00:05:00 +0000

If you need to read a file in Python, then you can use the open() built-in function to help you.

Let’s say that you have a file called somefile.txt with the following contents:

Hello, this is a test file
With some contents

How to Open a File and Read it in Python

We can read the contents of this file as follows:

f = open("somefile.txt", "r")
print(f.read())

This will print out the contents of the file.

How to Drop Columns in Pandas Only If Exists

Thu, 18 Aug 2022 00:05:00 +0000

If you have a Pandas DataFrame, and want to only drop columns if they exist, then you can do the following:

Add parameter errors to DataFrame.drop:

df = df.drop(['row_num','start_date','end_date','symbol'], axis=1, errors='ignore')

An example of how to Ignore Errors with `.drop()`

df = pd.DataFrame({'row_num':[1,2], 'w':[3,4]})
df = df.drop(['row_num','start_date','end_date','symbol'], axis=1, errors='ignore')
print (df)
   w
0  3
1  4

[Solved] An error occurred while calling o86.getDynamicFrame. Exception thrown in awaitResult:

Wed, 17 Aug 2022 00:05:00 +0000

If you are running a GlueJob in AWS and get the following error:

An error occurred while calling o86.getDynamicFrame. Exception thrown in awaitResult:

Then you need to view the CloudWatch logs to help you pinpoint where the problem is occuring.

How to solve the Exception thrown in `awaitResult`

It’s highly likely that the issue is in an expired IAM Role.

When a Role is created in IAM, the default maximum session duration is set to 1 hour.

AWS CDK Commands

Tue, 16 Aug 2022 00:05:00 +0000

The AWS Cloud Development Kit (CDK) comes with a list of commands that you need to know:


cdk list (ls)	Lists the stacks in the app
cdk synthesize (synth)	Synthesizes and prints the CloudFormation template for the specified stack(s)
cdk bootstrap	Deploys the CDK Toolkit staging stack; see Bootstrapping
cdk deploy	Deploys the specified stack(s)
cdk destroy	Destroys the specified stack(s)
cdk diff	Compares the specified stack with the deployed stack or a local CloudFormation template
cdk metadata	Displays metadata about the specified stack
cdk init	Creates a new CDK project in the current directory from a specified template
cdk context	Manages cached context values
cdk docs (doc)	Opens the CDK API reference in your browser
cdk doctor	Checks your CDK project for potential problems

You can learn more about the CDK here: https://docs.aws.amazon.com/cdk/v2/guide/cli.html

How to Make a Java Jar File Executable

Mon, 15 Aug 2022 00:05:00 +0000

Let’s say you have a Java project as follows:

package ms.ao.something;
public class MyProject {
    public static void main(String...args) throws Exception {
        System.out.println("Hello world!");
    }
}

Now you want to build this and make it a self contained executable Jar.

If you do a mvn clean install or mvn clean package, and try and run it as follows:

java -jar target/my-java-1.0-SNAPSHOT.jar

You will get the following error:

no main manifest attribute, in target/my-java-1.0-SNAPSHOT.jar

How to List All Resources in an AWS Account

Sun, 14 Aug 2022 00:05:00 +0000

If you need to see a list of all the resources in your AWS Account, then you need to look into the Tag Editor.

Step 1 – Tag Editor

Search for Tag Editor in the navigation search at the top of the AWS Console.

Select the Resource Groups & Tag Editor.

Step 2 – Find Resources

From the left hand menu, select Tag Editor

Step 3 – Filter your Search Requirements

From the Regions drop down, select All regions and then select All supported resource types from the Resource types drop down.

Fixed size left column and fluid right column both with 100% height in CSS

Sat, 13 Aug 2022 00:05:00 +0000

If you need two (2) columns and want the left column to be a fixed size, but the right column to automatically take the remaining size of the window, then you can use the following solution.

Follow the steps below, which include some CSS and some HTML.

The CSS for our solution

html, body {
  height: 100%;
  width: 100%;
  padding: 0;
  margin: 0;
}

.page-wrapper {
  height: 100%;
  position: relative;
}

.left-column {
  position:fixed; /* <-- This prevents scrolling */
  top:0;
  left:0;
  width:235px;
  height:100%;
  background:#090909;
}

.right-column {
  margin-left:235px;
  background:yellow;
  min-height:100%;  /* <-- Allows the content to grow */
}

The HTML for our solution

<div class="page-wrapper">
  <div class="left-column"></div>
  <div class="right-column">
    This is the content.
  </div>
</div>

How to Check if a Volume is Mounted in Bash

Fri, 12 Aug 2022 00:05:00 +0000

If you need to check if a volume is mounted in a Bash script, then you can do the following.

How to Check Mounted Volumes

First we need to determine the command that will be able to check.

This can be done with the /proc/mounts path.

How to Check if a Volume is Mounted in Bash

if grep -qs '/mnt/foo ' /proc/mounts; then
    echo "It's mounted."
else
    echo "It's not mounted."
fi

How to Check if a Volume is Mounted and Available

MNT_DIR=/mnt/foo
df_result=$(timeout 10 df "$MNT_DIR")
[[ $df_result =~ $MNT_DIR ]] 
if [ "$BASH_REMATCH" = "$MNT_DIR" ]
then
    echo "It's available."
else
    echo "It's not available."
fi

Another way of Checking Volume Mounts

mount \
    | cut -f 3 -d ' ' \
    | grep -q /mnt/foo \
  && echo "mounted" || echo "not mounted"

How to Determine if a Bash Variable is Empty

Thu, 11 Aug 2022 00:05:00 +0000

If you need to check if a bash variable is empty, or unset, then you can use the following code:

if [ -z "${VAR}" ];

The above code will check if a variable called VAR is set, or empty.

What does this mean?

Unset means that the variable has not been set.

Empty means that the variable is set with an empty value of "".

What is the inverse of `-z`?

The inverse of -z is -n.

How to Order by File Size using the du command in Linux

Wed, 10 Aug 2022 00:05:00 +0000

If you use the du command to list all the file sizes on Linux:

du
# or
du -h # Human readable

Then you would have noticed that they are not ordered by file size.

Instead you can pass that result to the sort command as follows:

du -h | sort -h

How to Join Multiple MySQL Tables in Python

Tue, 09 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

Presenting the data

let’s take two (2) tables as a demonstration for the code below.

Users – Table 1

{ id: 1, name: 'Carl', fav: 254},
{ id: 2, name: 'Emma', fav: 254},
{ id: 3, name: 'John', fav: 255},
{ id: 4, name: 'Hayley', fav:},
{ id: 5, name: 'Andrew', fav:}

Products – Table 2

How to Limit a MySQL Query in Python

Mon, 08 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Limit the Result Returned from MySQL in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
mycursor.execute("SELECT * FROM customers LIMIT 10")
myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Start From Another Position in MySQL from Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
mycursor.execute("SELECT * FROM customers LIMIT 10 OFFSET 5")
myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Update a MySQL Table in Python

Sun, 07 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Update a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "UPDATE customers SET address = 'Stoneleigh Place' WHERE address = 'Abbey Road'"
mycursor.execute(sql)
mydb.commit()

print(mycursor.rowcount, "record(s) affected")

Prevent SQL Injection in your Update Clause in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

sql = "UPDATE customers SET address = %s WHERE address = %s"
val = ("Stoneleigh Place", "Abbey Road")

mycursor.execute(sql, val)
mydb.commit()

print(mycursor.rowcount, "record(s) affected")

How to Drop a MySQL Table in Python

Sat, 06 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Delete/Drop a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "DROP TABLE customers"
mycursor.execute(sql)

How to Delete/Drop Only if MySQL Table Exists in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "DROP TABLE IF EXISTS customers"
mycursor.execute(sql)

How to Delete MySQL Records in Python

Fri, 05 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Delete MySQL Records in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "DELETE FROM customers WHERE address = 'The Rockies'"
mycursor.execute(sql)

mydb.commit()

print(mycursor.rowcount, "record(s) deleted")

Prevent SQL Injection in MySQL queries through Python

Specify the injected variable as the second argument to the execute command as below.

How to ORDER BY a MySQL Query in Python

Thu, 04 Aug 2022 21:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Sort the Result of a MySQL Query in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "SELECT * FROM customers ORDER BY name"
mycursor.execute(sql)

myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Change Direction of MySQL Order in Python

You can change the order of the sort by simply setting the order direction.

How to Filter WHERE MySQL Queries in Python

Wed, 03 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Select from MySQL with a Filter in Python

You simply specify the WHERE clause in your SQL statement as follows:

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
sql = "SELECT * FROM customers WHERE address ='London Road'"
mycursor.execute(sql)

myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Select and Filter Wildcard Characters in Python

To filter wildcard characters, you combine the WHEREand LIKE keywords, and place the % symbol where the wildcards would occur.

How to Select From MySQL in Python

Tue, 02 Aug 2022 00:05:00 +0000

First, you will need the mysql.connector. If you are unsure of how to get this setup, refer to How to Install MySQL Driver in Python.

How to Select From a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
mycursor.execute("SELECT * FROM customers")
myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Select Columns From a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
mycursor.execute("SELECT name, address FROM customers")
myresult = mycursor.fetchall()

for x in myresult:
  print(x)

How to Fetch Only a Single Row From MySQL in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()
mycursor.execute("SELECT * FROM customers")
myresult = mycursor.fetchone()

print(myresult)

How to Insert into a MySQL Table in Python

Mon, 01 Aug 2022 00:05:00 +0000

If you need to insert data into a MySQL table using Python, then look no further.

If you need to first learn about the mysql.connector and how to get this up and running, first take a look at the How to Install MySQL Driver in Python post before continuing.

How do Insert into a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

sql = "INSERT INTO customers (name, address) VALUES (%s, %s)"
val = ("Andrew", "Somewhere nice")
mycursor.execute(sql, val)

mydb.commit()

print(mycursor.rowcount, "record successfully inserted")

This will insert a single row into the MySQL table.

How to Create a Primary Key for a MySQL Database in Python

Sun, 31 Jul 2022 00:05:00 +0000

You can create a Primary Key for your MySQL database in Python as follows.

First, you need to know if the Primary Key already exists.

Option 1 – The Primary Key does not Exist

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

mycursor.execute("CREATE TABLE customers (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(255), address VARCHAR(255))")

Option 2 – The Primary Key already Exists

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

mycursor.execute("ALTER TABLE customers ADD COLUMN id INT AUTO_INCREMENT PRIMARY KEY")

How to Create a MySQL Table in Python

Sat, 30 Jul 2022 00:05:00 +0000

If you need to create a table in a MySQL database using Python, then you can do the following.

How to Create a MySQL Table in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "username",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

mycursor.execute("CREATE TABLE people (name VARCHAR(255), address VARCHAR(255))")

How to Check if a MySQL Table Exists in Python

import mysql.connector

mydb = mysql.connector.connect(
  host = "localhost",
  user = "yourusername",
  password = "YoUrPaSsWoRd",
  database = "your_database"
)

mycursor = mydb.cursor()

mycursor.execute("SHOW TABLES")

for x in mycursor:
  print(x)

How to Create a MySQL Database in Python

Fri, 29 Jul 2022 00:05:00 +0000

In order to create a MySQL database in Python, you first need to initiate a connection using the mysql.connector. You can learn about how to create a connection to MySQL here.

How to Create a Database in Python

Creating a database is simple.

First, make sure you have an active connection to your database, and then set a cursor.

Once you have this, issue the execute command to create your database.

How to Install MySQL Driver in Python

Thu, 28 Jul 2022 00:05:00 +0000

To begin using MySQL in Python, you need to do the following:

Step 1 – Install the MySQL Connector

Using pip, we can install the MySQL Connector package:

python -m pip install mysql-connector-python

Step 2 – Test the MySQL Connector

Create a Python file and import the new package:

import mysql.connector

Step 3 – Create a Connection to the MySQL Database

Now you can create a connection to your MySQL database.

Create a file called app.py and place the following inside:

How to Resize an AWS EBS Volume in Bash

Wed, 27 Jul 2022 00:05:00 +0000

If you need to resize an EBS volume in AWS, you can do so using bash.

Step 1 – Create a `bash` file

Create a bash file called resize.sh:

#!/bin/bash

SIZE=${1:-20}

INSTANCEID=$(curl http://169.254.169.254/latest/meta-data/instance-id)
REGION=$(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/\(.*\)[a-z]/\1/')

VOLUMEID=$(aws ec2 describe-instances \
  --instance-id $INSTANCEID \
  --query "Reservations[0].Instances[0].BlockDeviceMappings[0].Ebs.VolumeId" \
  --output text \
  --region $REGION)

aws ec2 modify-volume --volume-id $VOLUMEID --size $SIZE

while [ \
  "$(aws ec2 describe-volumes-modifications \
    --volume-id $VOLUMEID \
    --filters Name=modification-state,Values="optimizing","completed" \
    --query "length(VolumesModifications)"\
    --output text)" != "1" ]; do
sleep 1
done

if [[ -e "/dev/xvda" && $(readlink -f /dev/xvda) = "/dev/xvda" ]]
then
  sudo growpart /dev/xvda 1

  STR=$(cat /etc/os-release)
  SUB="VERSION_ID=\"2\""
  if [[ "$STR" == *"$SUB"* ]]
  then
    sudo xfs_growfs -d /
  else
    sudo resize2fs /dev/xvda1
  fi

else
  sudo growpart /dev/nvme0n1 1

  STR=$(cat /etc/os-release)
  SUB="VERSION_ID=\"2\""
  if [[ "$STR" == *"$SUB"* ]]
  then
    sudo xfs_growfs -d /
  else
    sudo resize2fs /dev/nvme0n1p1
  fi
fi

Step 2 – Run the `bash` file specifying the new size

Now that you have the bash file, you can run the bash file along with specifying the new size of the desired volume:

How to get all checked checkboxes in Javascript

Tue, 26 Jul 2022 00:05:00 +0000

If you need to get all the checked checkboxes using Javascript, then you can do the following:

Option 1 – In a single line

const checkedBoxes = document.querySelectorAll('input[name=mycheckboxes]:checked');

Option 2 – Another one liner

const data = [...document.querySelectorAll('.mycheckboxes:checked')].map(e => e.value);

Option 3 – Create a helper function

function getCheckedBoxes(checkboxName) {
  var checkboxes = document.getElementsByName(checkboxName);
  var checkboxesChecked = [];

  for (var i=0; i<checkboxes.length; i++) {
     if (checkboxes[i].checked) checkboxesChecked.push(checkboxes[i]);
     }
  }
  return checkboxesChecked.length > 0 ? checkboxesChecked : null;
}

Now you simply call the function:

How to Setup Credential Helper for AWS CodeCommit

Mon, 25 Jul 2022 00:05:00 +0000

AWS CodeCommit is a git code repository service by Amazon Web Services.

You will want to clone your repository and setup your remotes using credential helper.

Step 1 – Setup Credential Helper

git config --global credential.helper '!aws codecommit credential-helper $@'
git config --global credential.UseHttpPath true

This will write to your local user’s ~/.gitconfig, and the file will look something like:

[credential]    
    helper = !aws --profile CodeCommitProfile codecommit credential-helper $@
    UseHttpPath = true

You can edit this file by running the following git command:

How to Flex Grid 2 Columns using CSS

Sun, 24 Jul 2022 00:05:00 +0000

If you would like to flex grid 2 columns in CSS then you need three (3) divs.

Step 1 – Set your HTML template

Create some HTML with this layout.

<div class="Parent">
  <div class="child1">
      <h1>Left</h1>
  </div>
  <div class="child2">
      <h1>RIGHT</h1>
  </div>
</div>

Step 2 – Container Div

Create a Parent div that uses the Flexbox display model.

.Parent {
  display: flex;
  flex-direction: row;
}

Step 3 – Child Divs

Create two (2) divs that are both 50% of the parent container.

How to Create a Hashtag Generator in Javascript

Sat, 23 Jul 2022 00:05:00 +0000

If you want to create a hashtag generator in Javascript, then you can do the following:

function generateHashtag(string) {
  if (string.trim() === '') return false;

  const stringWithCamelCase = string
    .split(' ')
    .map(word => word.charAt(0).toUpperCase() + word.slice(1))
    .join('');

  const stringWithHashtag = `#${stringWithCamelCase.trim()}`;

  return stringWithHashtag.length > 140 ? false : stringWithHashtag;
}

How to use the Hashtag Generator

const hashtag = generateHashtag("My New Hashtag !")

console.log(hashtag);
// #MyNewHashtag!

How to Confirm before Leaving Page in Javascript

Fri, 22 Jul 2022 00:05:00 +0000

You can implement a function to be called before the user leaves a page with Javascript as follows:

window.onbeforeunload = function(e) {
  return "Do you want to exit this page?";
};

This is a typically solution for when you want the user to confirm their changes are saved before allowing them to close the current page in editing tools.

What are the multiples of 3 from 1 to 1000

Thu, 21 Jul 2022 00:05:00 +0000

If you need to calculate the multiples of 3, starting from 1 up until 1000, then you can use the following code:

n = 1
v = []
while n <= 1000:
  v.append(n)
  n = n + 3

This will generate the list of numbers which are the multiples of 3 from 1 to 1000:

1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, 52, 55, 58, 61, 64, 67, 70, 73, 76, 79, 82, 85, 88, 91, 94, 97, 100, 103, 106, 109, 112, 115, 118, 121, 124, 127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 169, 172, 175, 178, 181, 184, 187, 190, 193, 196, 199, 202, 205, 208, 211, 214, 217, 220, 223, 226, 229, 232, 235, 238, 241, 244, 247, 250, 253, 256, 259, 262, 265, 268, 271, 274, 277, 280, 283, 286, 289, 292, 295, 298, 301, 304, 307, 310, 313, 316, 319, 322, 325, 328, 331, 334, 337, 340, 343, 346, 349, 352, 355, 358, 361, 364, 367, 370, 373, 376, 379, 382, 385, 388, 391, 394, 397, 400, 403, 406, 409, 412, 415, 418, 421, 424, 427, 430, 433, 436, 439, 442, 445, 448, 451, 454, 457, 460, 463, 466, 469, 472, 475, 478, 481, 484, 487, 490, 493, 496, 499, 502, 505, 508, 511, 514, 517, 520, 523, 526, 529, 532, 535, 538, 541, 544, 547, 550, 553, 556, 559, 562, 565, 568, 571, 574, 577, 580, 583, 586, 589, 592, 595, 598, 601, 604, 607, 610, 613, 616, 619, 622, 625, 628, 631, 634, 637, 640, 643, 646, 649, 652, 655, 658, 661, 664, 667, 670, 673, 676, 679, 682, 685, 688, 691, 694, 697, 700, 703, 706, 709, 712, 715, 718, 721, 724, 727, 730, 733, 736, 739, 742, 745, 748, 751, 754, 757, 760, 763, 766, 769, 772, 775, 778, 781, 784, 787, 790, 793, 796, 799, 802, 805, 808, 811, 814, 817, 820, 823, 826, 829, 832, 835, 838, 841, 844, 847, 850, 853, 856, 859, 862, 865, 868, 871, 874, 877, 880, 883, 886, 889, 892, 895, 898, 901, 904, 907, 910, 913, 916, 919, 922, 925, 928, 931, 934, 937, 940, 943, 946, 949, 952, 955, 958, 961, 964, 967, 970, 973, 976, 979, 982, 985, 988, 991, 994, 997, 1000

How to Count Files in Directory on Linux

Wed, 20 Jul 2022 00:05:00 +0000

If you need to count how many files are in a directory on Linux, then you can use a combination of the ls command to list all the files, and the wc command to count how many lines are printed:

Option 1 – Using `wc`

ls | wc -l

You can specify a directory as follows:

ls <directory> | wc -l

Option 2 – Using `find`

You can count files recursively by using the find command:

How to Read a File Line by Line in Java

Tue, 19 Jul 2022 00:05:00 +0000

If you need to read a file line by line in Java, then you can use one of the following three (3) options.

Option 1

You can use the FileReader and BufferedReader packages as follows:

File file = new File("./your/file.txt");

try (FileReader fr = new FileReader(file);
  BufferedReader br = new BufferedReader(fr);) {
  String line;
  while ((line = br.readLine()) != null) {
    System.out.println(line);
  }
} catch (IOException e) {
  e.printStackTrace();
}

Option 2

You can also read the lines using Files and Paths as follows:

How can I clear or empty a StringBuilder

Mon, 18 Jul 2022 00:05:00 +0000

You can use Java’s StringBuilder to create and manipulate Strings as follows:

StringBuilder sb = new StringBuilder();
sb.append("Some").append(" ").append("String");
System.out.println(sb.toString());

// "Some String"

The following three (3) options allow you to clear or empty a StringBuilder.

Option 1 – using `setLength`

sb.setLength(0);

Option 2 – reinstantiating

sb = new StringBuilder();

Option 3 – using `delete`

sb.delete(0, sb.length());

How to Approve a SageMaker model in AWS CLI

Sun, 17 Jul 2022 00:05:00 +0000

Sometimes you will need to manually approve a SageMaker model package from the AWS CLI.

Step 1 – Get a list of the available packages

aws sagemaker list-model-packages --model-package-group-name "the-model-package-group"

This will produce the following output:

{
  "ModelPackageSummaryList": [
    {
      "ModelPackageGroupName": "...",
      "ModelPackageVersion": "...",
      "ModelPackageArn": "the-arn-we-will-use-below",
      "ModelPackageDescription": "...",
      "CreationTime": "...",
      "ModelPackageStatus": "Completed",
      "ModelApprovalStatus": "PendingManualApproval"
    },
    ...
  ]
}

Step 2 – Approve the model

aws sagemaker update-model-package --model-package-arn <ARN-FROM-ABOVE> --model-approval-status Approved

How to Assume Role across Accounts in AWS

Sat, 16 Jul 2022 00:05:00 +0000

If you need to assume role between AWS accounts, or allow an account to assume a role and use resources in another AWS account, then you need to create a role and attach the following policy.

The following two (2) steps creates a Trust Relationship between the accounts.

Step 1 – In the `Source` Account

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": [
      "sts:AssumeRole"
    ],
    "Resource": [
      "arn:aws:iam::DESTINATION-ACCOUNT-ID:role/DESTINATION-ROLENAME"
    ]
  }]
}

Step 2 – In the `Destination` Account

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Principal": {
      "AWS": "arn:aws:iam::SOURCE-ACCOUNT-ID:role/SOURCE-USERNAME"
    },
    "Action": "sts:AssumeRole"
  }]
}

How to Style an Element using Javascript

Fri, 15 Jul 2022 00:05:00 +0000

If you need to style an element using Javascript then you can use the style object to support all your CSS needs.

<html>
  <body>

    <p id="p1">Hello World!</p>

    <script>
      document.getElementById("p1").style.color = "red";
    </script>

    <p>The paragraph above was changed by a script.</p>

  </body>
</html>

If you need to do this purely in a Javascript file itself, then:

// Get a reference to the element
var myElement = document.querySelector("#p1");

// Now you can update the CSS attributes
myElement.style.color = "red";
myElement.style.backgroundColor = "yellow";

Note that where CSS properties would use dashes to separate words, like background-color, Javascript instead uses camel casing and drops the space.

How to Wait 1 Second in Javascript

Thu, 14 Jul 2022 00:05:00 +0000

If you need your Javascript code to wait one (1) second (or more) while executing, then there are a couple of ways to achieve this.

Option 1 – Creating a `delay` Promise

function delay(time) {
  return new Promise(resolve => setTimeout(resolve, time));
}

delay(1000).then(() => console.log('ran after 1 second elapsed'));

Option 2 – Using `setTimeout`

setTimeout(function(){ 
  console.log("Ready")
}, 1000);

Option 3 – Using an `async` Promise

async function test() {
  console.log('start timer');
  await new Promise(resolve => setTimeout(resolve, 1000));
  console.log('after 1 second');
}

test();

Option 4 – Creating a custom `sleep` function

function sleep(num) {
  let now = new Date();
  const stop = now.getTime() + num;
  while(true) {
    now = new Date();
    if(now.getTime() > stop) return;
  }
}

sleep(1000)
console.log('delay 1 second');

How to use forEach method in Javascript

Wed, 13 Jul 2022 00:05:00 +0000

Arrays come with a useful forEach function that allows you to loop through the array.

var colors = ['red', 'blue', 'green'];

colors.forEach(function(color) {
  console.log(color);
});

// red
// blue
// green

You can also get the index in each loop as follows:

const colors = ['red', 'blue', 'green'];

colors.forEach((item, index)=>{
  console.log(index, item)
});

// 0 'red'
// 1 'blue'
// 2 'green'

How to Remove an Element from an Array in Javascript

Tue, 12 Jul 2022 00:05:00 +0000

If you need to remove an element from an array in Javascript, then you can use one of the following five (5) options:

Option 1 – Use `splice` to remove an element

Example 1 using splice:

var colors = ["red","blue","car","green"];
var carIndex = colors.indexOf("car");
colors.splice(carIndex, 1);

// colors = ["red","blue","green"]

Example 2 using splice:

var myArray = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

// Remove Sunday -- index 0 and Monday -- index 1
myArray.splice(0,2)

Option 2 – Use `filter` to remove an element

var myArray = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
let itemToBeRemoved = ["Sunday", "Monday"]
var filteredArray = myArray.filter(item => !itemToBeRemoved.includes(item))

Option 3 – Use `pop` to remove an element

let dailyActivities = ['work', 'eat', 'sleep', 'exercise'];

// remove the last element
dailyActivities.pop();
console.log(dailyActivities); // ['work', 'eat', 'sleep']

// remove the last element from ['work', 'eat', 'sleep']
const removedElement = dailyActivities.pop();

// get removed element
console.log(removedElement); // 'sleep'
console.log(dailyActivities);  // ['work', 'eat']

Option 4 – Use `remove` to remove an element

array.remove(number);

Option 5 – Change `length` to remove elements

var arr = [1, 2, 3, 4, 5, 6];

arr.length = 4;

// [1, 2, 3, 4]

How to get the Alphabet as Array in Javascript

Mon, 11 Jul 2022 00:05:00 +0000

If you need to get an array of alphabetical letters in Javascript then you can use one of the following:

Option 1 – Explicitly define the array first

const alphabet = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];

Option 2 – Split a string of alphabetical characters

const alphabetArray = "abcdefghijklmnopqrstuvwxyz".split("");

Option 3 – Split a string and UpperCase characters

const alphabetArrayUp = toUpperCase("abcdefghijklmnopqrstuvwxyz").split("");

The Power of Two (2) Table

Sun, 10 Jul 2022 00:05:00 +0000

With the Power of Two, you can ask the following:

How do you find the powers of 2?
What does the power of 2 stand for?
How much is the power of 2?

The Power of Two (2) Table (Powers of Two)

Power	Value
	1
1	2
2	4
3	8
4	16
5	32
6	64
7	128
8	256
9	512
10	1,024
11	2,048
12	4,096
13	8,192
14	16,384
15	32,768
16	65,536
17	131,072
18	262,144
19	524,288
20	1,048,576
21	2,097,152
22	4,194,304
23	8,388,608
24	16,777,216
25	33,554,432
26	67,108,864
27	134,217,728
28	268,435,456
29	536,870,912
30	1,073,741,824
31	2,147,483,648
32	4,294,967,296
33	8,589,934,592
34	17,179,869,184
35	34,359,738,368
36	68,719,476,736
37	137,438,953,472
38	274,877,906,944
39	549,755,813,888
40	1,099,511,627,776
41	2,199,023,255,552
42	4,398,046,511,104
43	8,796,093,022,208
44	17,592,186,044,416
45	35,184,372,088,832
46	70,368,744,177,664
47	140,737,488,355,328
48	281,474,976,710,656
49	562,949,953,421,312
50	1,125,899,906,842,624
51	2,251,799,813,685,248
52	4,503,599,627,370,496
53	9,007,199,254,740,992
54	18,014,398,509,481,984
55	36,028,797,018,963,968
56	72,057,594,037,927,936
57	144,115,188,075,855,872
58	288,230,376,151,711,744
59	576,460,752,303,423,488
60	1,152,921,504,606,846,976
61	2,305,843,009,213,693,952
62	4,611,686,018,427,387,904
63	9,223,372,036,854,775,808
64	18,446,744,073,709,551,616
65	36,893,488,147,419,103,232
66	73,786,976,294,838,206,464
67	147,573,952,589,676,412,928
68	295,147,905,179,352,825,856
69	590,295,810,358,705,651,712
70	1,180,591,620,717,411,303,424
71	2,361,183,241,434,822,606,848
72	4,722,366,482,869,645,213,696
73	9,444,732,965,739,290,427,392
74	18,889,465,931,478,580,854,784
75	37,778,931,862,957,161,709,568
76	75,557,863,725,914,323,419,136
77	151,115,727,451,828,646,838,272
78	302,231,454,903,657,293,676,544
79	604,462,909,807,314,587,353,088
80	1,208,925,819,614,629,174,706,176
81	2,417,851,639,229,258,349,412,352
82	4,835,703,278,458,516,698,824,704
83	9,671,406,556,917,033,397,649,408
84	19,342,813,113,834,066,795,298,816
85	38,685,626,227,668,133,590,597,632
86	77,371,252,455,336,267,181,195,264
87	154,742,504,910,672,534,362,390,528
88	309,485,009,821,345,068,724,781,056
89	618,970,019,642,690,137,449,562,112
90	1,237,940,039,285,380,274,899,124,224
91	2,475,880,078,570,760,549,798,248,448
92	4,951,760,157,141,521,099,596,496,896
93	9,903,520,314,283,042,199,192,993,792
94	19,807,040,628,566,084,398,385,987,584
95	39,614,081,257,132,168,796,771,975,168
96	79,228,162,514,264,337,593,543,950,336
97	158,456,325,028,528,675,187,087,900,672
98	316,912,650,057,057,350,374,175,801,344
99	633,825,300,114,114,700,748,351,602,688
100	1,267,650,600,228,229,401,496,703,205,376

The Power of Two (2) Tables from 1 to 100

Below you will find the Power of Two (2) tables from 1 to 100.

How to get the Screen Width in Javascript

Sat, 09 Jul 2022 00:05:00 +0000

Javascript gives a few options to determine the screen width.

When we say screen, we mean the browser window’s width itself.

Option 1 – Using Native Javascript

Using native Javascript objects, we can find the innerWidth and innerHeight:

var w = window.innerWidth;
var h = window.innerHeight;

The window object also allows for:

window.screen.width
// or simply
screen.width

We can write some code to tell us the width and height with fallbacks:

var win = window,
    doc = document,
    docElem = doc.documentElement,
    body = doc.getElementsByTagName('body')[0],
    x = win.innerWidth || docElem.clientWidth || body.clientWidth,
    y = win.innerHeight|| docElem.clientHeight|| body.clientHeight;
alert(x + ' × ' + y);

Option 2 – Get Width using jQuery

$(window).width()

You can use this as follows:

How to Read a File in Rust

Fri, 08 Jul 2022 00:05:00 +0000

If you need to read a file in Rust, then you can use the fs package from the standard library:

use std::fs;

fn main() {
    let contents = fs::read_to_string(filename)
        .expect("Something went wrong reading the file");

    println!("With text:\n{}", contents);
}

How to Convert Array to String in Java

Thu, 07 Jul 2022 00:05:00 +0000

If you need to convert an array to a string in Java, then you could look at a solution like this:

String stringArray[] = {"Hello ", " world", " this", " is", " a", " test"};
StringBuffer sb = new StringBuffer();
for(int i = 0; i < stringArray.length; i++) {
   sb.append(stringArray[i]);
}
String str = sb.toString();
System.out.println(str);

Or you could do something simple like this:

String str = String.join(",", arr);

How to Join Two Strings Together in Golang

Wed, 06 Jul 2022 00:05:00 +0000

If you need to join two (2) strings together in Golang, you can do the following, using the + concatenation operator:

package main
import ( "fmt")

func main() {  
  message1 := "Join Strings"
  message2 := "Together"

  result := message1 + " " + message2

  fmt.Println(result)
}

How to Recursively Delete all Files in an AWS S3 Bucket

Tue, 05 Jul 2022 00:05:00 +0000

If you need to recursively delete all files in an AWS S3 bucket, then you can do the following:

aws s3 rm --recursive s3://your-bucket-name/foo/bar/

If you only want to delete an specific object from AWS S3:

aws s3 rm s3://your-bucket-name/foo/bar/item.txt

How to Execute Linux Commands in Golang

Mon, 04 Jul 2022 00:05:00 +0000

If you want to execute linux commands in Golang, then you can use exec.Command:

cmd := exec.Command("echo", "hello world")
res, _ := cmd.CombinedOutput()
fmt.Println(string(res))

How to Check for Prime Numbers using Golang

Sun, 03 Jul 2022 00:05:00 +0000

If you need to check for Prime Numbers in Golang, then you can use the following method:

const n = 1212121
if big.NewInt(n).ProbablyPrime(0) {
  fmt.Println(n, "is prime")
} else {
  fmt.Println(n, "is not prime")
}

How to Raise a Number to a Power in Golang

Sat, 02 Jul 2022 00:05:00 +0000

If you need to raise a number to a power in Golang, then you can use the math.Pow function:

package main  
import (
  "math"  
)  
  
func main() {  
  var exponent, base float64
  output := math.Pow(base, exponent)  
}

How to get CPU Frequency in Linux

Fri, 01 Jul 2022 00:05:00 +0000

If you need to get the CPU Frequency in Linux, then you can run the following command:

watch -n.1 "grep \"^[c]pu MHz\" /proc/cpuinfo"

How to Disable Warning with Python Pandas

Thu, 30 Jun 2022 00:05:00 +0000

How can python pandas disable warnings?

If you need to disable warnings with Pandas on Python, then you can use the warnings module and ignore the filter as follows:

import warnings
warnings.filterwarnings('ignore')

How to Get all Caps Alphabet as List in Python

Wed, 29 Jun 2022 00:05:00 +0000

If we take the following list:

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

How do we extract only the UpperCase letters of a given word?

How to get only the Capital Letters from a String

word = 'AbcDefgHijkL'
result = re.findall('([A-Z])', word)
print(result)
# ['A', 'D', 'H', 'L']

[Solved] Error creating RDS DB Instance: IAM role ARN value is not value or does not include the required permissions for: ENHANCED_MONITORING

Tue, 28 Jun 2022 00:05:00 +0000

When you are trying to create an RDS database and you get the dreaded error message:

IAM role ARN value is invalid or does not include the required permissions for: ENHANCED_MONITORING

Then you need to make sure that you are assuming the correct service principle:

monitoring.rds.amazonaws.com

Your code should look something like this:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Effect": "Allow",
      "Principal": {
        "Service": "cloudwatch.amazonaws.com"
      }
    },
    {
      "Action": "sts:AssumeRole",
      "Effect": "Allow",
      "Principal": {
        "Service": "monitoring.rds.amazonaws.com"
      }
    }
  ]
}

How to create an AWS Lambda in Terraform

Mon, 27 Jun 2022 00:05:00 +0000

Step 1 – Lambda Code in Python

The following code expects a python file with the contents as follows in a file called python/script1.py:

def lambda_handler(event, context):
    return {
        'code': 200,
        'message': 'Triggered'
    }

Step 2 – Lambda Code in Terraform

Now we create the lambda.tf:

data "archive_file" "zip_python_code_create" {
  type        = "zip"
  source_file = "python/script1.py"
  output_path = "python/script1.zip"
}

resource "aws_lambda_function" "lambda_script1" {
  filename      = "python/script1.zip"
  function_name = "LambdaScript1"
  role          = aws_iam_role.lambda_role.arn
  description   = "LambdaScript1"
  handler       = "create.lambda_handler"
  runtime       = "python3.8"
  depends_on    = [aws_iam_role_policy_attachment.attach_iam_policy_to_iam_role]
}

Step 3 – IAM and Permissions in Terraform

We need to specify the permissions for the Lambda:

[Solved] Instance Profile already exists in Terraform

Sun, 26 Jun 2022 00:05:00 +0000

If you get the Instance Profile already exists error when running your Terraform apply, then it is either because an instance profile with that name already existed in the account, or because the previous terraform destroy did not remove it.

Step 1 – Identify the Instance Profiles in the account

aws iam list-instance-profiles

Step 2 – Delete the Instance Profile/s

aws iam delete-instance-profile --instance-profile-name <name-of-instance-profile>

[Solved] An error occurred (UnauthorizedException) when calling ListAccounts operation: Session token not found or invalid

Sat, 25 Jun 2022 00:05:00 +0000

If you are using aws configure sso to populate your ~/.aws/credentials file and you get the following error when you try and reauthorize, then you can solve this problem as follows:

An error occurred (UnauthorizedException) when calling ListAccounts operation: Session token not found or invalid

Step 1 – Logout from SSO

aws sso logout

Step 2 – Reconfigure SSO with previous defaults

aws configure sso

How to Match Multiple Strings with grep

Fri, 24 Jun 2022 00:05:00 +0000

If you need to match a string in a file, then grep is your friend.

An example of using `grep`

Let’s take a file called somefile.txt

this
is
a
test
that
looks
for
something

We can look for the string something in this file using grep:

cat somefile.txt | grep something
# something

But what if we want to look for both something and this?

An example of using multiple `grep`s

It’s pretty easy, we just pass the -E flag, which is short for --extended-regexp, and separate our strings with a pipe |.

How to Invoke an AWS Lambda from the CLI

Thu, 23 Jun 2022 00:05:00 +0000

If you want to invoke an AWS Lambda from your CLI, then the best option is to have the AWS CLI installed.

Getting started with the AWS CLI – AWS Command Line Interface (amazon.com)

Once this is installed, you can invoke Lambdas as follows:

Setting your AWS Region

It is recommended to always set your AWS region in an environment variable called AWS_REGION

How to Exit if a Bash Variable in Not Set

Wed, 22 Jun 2022 00:05:00 +0000

Sometimes you might want to exit a command if a variable is not set in Bash.

You can do this as follows:

if [ -z "$VARIABLE_NAME" ]; then echo "VARIABLE_NAME is not set"; exit 1; fi

How to Force Gitlab pipeline to fail on condition

Tue, 21 Jun 2022 00:05:00 +0000

if you have a conditional in your Gitlab pipeline stage that checks if something has succeeded or failed, then you can use this to pass or fail your pipeline stage.

Option 1 – Fail on String Found

if cat log.txt | grep "Failure Summary" ; then exit 1 ; else exit 0 ; fi

This will fail the pipeline if it find a string matching Failure Summary in a file called log.txt in the current stage.

How to run AWS CLI commands based on AWS CLI Version in Bash

Mon, 20 Jun 2022 00:05:00 +0000

If you find yourself having the requirements to support both AWS CLI v1 and v2 simultaneously, then you can use the following conditional in Bash to only run the specific version required:

AWS_VERSION=$(aws --version | gawk '{print $1}' | gawk -F/ '{print $2}' | gawk -F. '{print $1}')
if [ AWS_VERSION == "1" ]
then
    aws lambda invoke --function-name YourFunction --payload $(echo '{"k":"v"}') response.json
else
    aws lambda invoke --function-name YourFunction --cli-binary-format raw-in-base64-out --payload '{"k":"v"}' response.json
fi

This can be useful for deploying to environments where you cannot guarantee the AWS CLI version installed. Such as distributed pipelines, or customer environments.

[Solved] Unknown options: –cli-binary-format AWS CLI

Sun, 19 Jun 2022 00:05:00 +0000

If you have tried calling the AWS CLI and got the following error:

Unknown options: --cli-binary-format

Then it is because you are using the AWS CLI v1 and should be using the newer AWS CLI v2.

Another error that you will see along with this is:

An error occurred (InvalidRequestContentException) when calling the Invoke operation: Could not parse request body into json: Could not parse payload into json: Unrecognized token 'eyJwYXRoIjoiJEdMAAAAIgfQo': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')

An example that fails on AWS CLI v1

aws lambda invoke --function-name YourFunction --cli-binary-format raw-in-base64-out --payload '{"yourKey":"yourValue"}'

How to fix this error on AWS CLI v1

aws lambda invoke --function-name YourFunction --region eu-west-1 --payload '{"yourKey":"yourValue"}' response.json

How to fix this error by Upgrading to AWS CLI v2

You can follow the guide directly to upgrade your CLI from v1 to v2 here Migrating from AWS CLI version 1 to version 2 – AWS Command Line Interface (amazon.com)

How to Generate Random Strings with Dash in-between in Python

Sat, 18 Jun 2022 00:05:00 +0000

If you need to generate a random string that looks something like this: VUNBXJ-230411, then you can use the following random generator:

import random, string

def generate_random_string_with_dash():
    rand = "{0}-{1}".format(''.join(random.choice(string.ascii_uppercase) for x in range(6)),
                            ''.join(random.choice(string.digits) for x in range(6)))
    return rand

You simply call the above as follows:

print( generate_random_string_with_dash() )
# JJXFNS-420809

If you need to adjust the length of string A and B, then you can change the value in the range above from something other than 6.

How to Check OS version and flavor in Linux

Fri, 17 Jun 2022 00:05:00 +0000

If you need to check the version and flavour of the running Linux instance, then you can try the below commands:

cat /etc/os-release
lsb_release -a
hostnamectl

How to use a Backend-Config File for Terraform S3 State Configuration

Thu, 16 Jun 2022 00:05:00 +0000

If you are using S3 as the backend for your state management in Terraform, then you can create environment specific configuration files where you store the bucket, region among other things to be pulled in automatically when switching environments.

Step 1 – Create environment specific configs

Create a dev.conf file with the following content:

bucket = "your-bucket"
region = "your-aws-region"
key    = "path/to/key"

Step 2 – Set the `terraform` `backend`

In your main.tf, providers.tf or state.tf file, specify the following:

How to Refresh State in Terraform

Wed, 15 Jun 2022 00:05:00 +0000

Sometimes your infrastructure may be out of sync with your Terraform state because resources may have been amended or deleted manually.

For this you can refresh the Terraform state.

Using the `refresh` command

terraform refresh [options]

Why this command may appear strange at first, not that it is merely an alias for:

terraform apply -refresh-only -auto-approve

If you don’t want to auto-approve the transaction, then you can perform a refresh as follows:

How to get the Length of an Array in C

Tue, 14 Jun 2022 00:05:00 +0000

There isn’t really a standard way to get the length of array in C. This means you need to do some additional work to achieve getting the length of an array when using C.

Creating and Looping through an Array in C

Usually you would create an array as follows:

int items[5] = {1, 2, 3, 4, 5};

You could always define the size right off the bat:

const int SIZE = 5;
int items[SIZE] = {1, 2, 3, 4, 5};

This way if you need to loop through the array later on, you can use your SIZE variable.

How to write If/Else Statements in Terraform

Mon, 13 Jun 2022 00:05:00 +0000

If/Else statements are conditional statements that perform decisions based on some known state, or variable.

Terraform allows you to perform these if/else statements using a ternary operation which have become popular as short-form if/else statements in many programming languages.

Where a language would write something similar to:

let truthy = false
if (something == "value") {
  truthy = true
} else {
  truthy = false
}

The ternary alternative would be:

How to Reset Udemy Progress

Sun, 12 Jun 2022 00:05:00 +0000

If you need to redo a Udemy course and you would like to reset the course’s progress, then you can use the following Javascript snippet below.

You have to do this manually because Udemy does not provide native functionality to do this.

Step 1 – Navigate to Udemy in a web browser

Make sure you are on the course content page you would like to reset.

Step 2 – Open up the developer tools

You will need to run a Javascript snippet, so press the following keyboard shortcuts, or right-click and select Inspect:

How to Get Last Digit of a Large Number in C

Sat, 11 Jun 2022 00:05:00 +0000

The challenge

Define a function that takes in two non-negative integers aa_a_ and bb_b_ and returns the last decimal digit of aba^b_a__b_. Note that aa_a_ and bb_b_ may be very large!

For example, the last decimal digit of 979^797 is 999, since 97=47829699^7 = 478296997=4782969. The last decimal digit of (2200)2300({2^{200}})^{2^{300}}(2200)2300, which has over 109210^{92}1092 decimal digits, is 666. Also, please take 000^000 to be 111.

You may assume that the input will always be valid.

[Solved] Network interface is in use by another service in AWS

Fri, 10 Jun 2022 00:05:00 +0000

If you have tried to delete a Security Group, or VPC, or various other resources and you get the dreaded Network interface is in use by another service error, then you can resolve this by deleting the resource through the API.

How to delete the Network Interface (`ENI`)

aws ec2 delete-network-interface --network-interface-id eni-xxxxx

Replace the eni-xxxxx with the ENI id that you are struggling to delete.

How to find what services are using the `ENI`

#!/bin/bash
vpc="vpc-xxxxxxxxxxxxx" 
aws ec2 describe-internet-gateways --filters 'Name=attachment.vpc-id,Values='$vpc | grep InternetGatewayId
aws ec2 describe-subnets --filters 'Name=vpc-id,Values='$vpc | grep SubnetId
aws ec2 describe-route-tables --filters 'Name=vpc-id,Values='$vpc | grep RouteTableId
aws ec2 describe-network-acls --filters 'Name=vpc-id,Values='$vpc | grep NetworkAclId
aws ec2 describe-vpc-peering-connections --filters 'Name=requester-vpc-info.vpc-id,Values='$vpc | grep VpcPeeringConnectionId
aws ec2 describe-vpc-endpoints --filters 'Name=vpc-id,Values='$vpc | grep VpcEndpointId
aws ec2 describe-nat-gateways --filter 'Name=vpc-id,Values='$vpc | grep NatGatewayId
aws ec2 describe-security-groups --filters 'Name=vpc-id,Values='$vpc | grep GroupId
aws ec2 describe-instances --filters 'Name=vpc-id,Values='$vpc | grep InstanceId
aws ec2 describe-vpn-connections --filters 'Name=vpc-id,Values='$vpc | grep VpnConnectionId
aws ec2 describe-vpn-gateways --filters 'Name=attachment.vpc-id,Values='$vpc | grep VpnGatewayId
aws ec2 describe-network-interfaces --filters 'Name=vpc-id,Values='$vpc | grep NetworkInterfaceId

How to Uninstall npm packages

Thu, 09 Jun 2022 00:05:00 +0000

We typically install an npm package as follows:

npm install <package_name>

But how do we uninstall an npm package?

How to uninstall an npm package

This will uninstall an npm package that was installed in your project.

Just make sure to run the command from the root directory of your project.

npm uninstall <package_name>

This will remove the package from the node_modules directory and will also remove the reference to it from the package.json file.

RBG Color Codes

Wed, 08 Jun 2022 00:05:00 +0000

Often you need to reference an HTML/CSS Color Code in RGB or Hex. This is known as rgb color codes.

Below is an easy-to-use table to find the appropriate RGB and Hex Color Codes.

Name	#RRGGBB (Hex Code)	R,G,B (Decimal code)
maroon	#800000	(128,0,0)
dark red	#8B0000	(139,0,0)
brown	#A52A2A	(165,42,42)
firebrick	#B22222	(178,34,34)
crimson	#DC143C	(220,20,60)
red	#FF0000	(255,0,0)
tomato	#FF6347	(255,99,71)
coral	#FF7F50	(255,127,80)
indian red	#CD5C5C	(205,92,92)
light coral	#F08080	(240,128,128)
dark salmon	#E9967A	(233,150,122)
salmon	#FA8072	(250,128,114)
light salmon	#FFA07A	(255,160,122)
orange red	#FF4500	(255,69,0)
dark orange	#FF8C00	(255,140,0)
orange	#FFA500	(255,165,0)
gold	#FFD700	(255,215,0)
dark golden rod	#B8860B	(184,134,11)
golden rod	#DAA520	(218,165,32)
pale golden rod	#EEE8AA	(238,232,170)
dark khaki	#BDB76B	(189,183,107)
khaki	#F0E68C	(240,230,140)
olive	#808000	(128,128,0)
yellow	#FFFF00	(255,255,0)
yellow green	#9ACD32	(154,205,50)
dark olive green	#556B2F	(85,107,47)
olive drab	#6B8E23	(107,142,35)
lawn green	#7CFC00	(124,252,0)
chart reuse	#7FFF00	(127,255,0)
green yellow	#ADFF2F	(173,255,47)
dark green	#006400	(0,100,0)
green	#008000	(0,128,0)
forest green	#228B22	(34,139,34)
lime	#00FF00	(0,255,0)
lime green	#32CD32	(50,205,50)
light green	#90EE90	(144,238,144)
pale green	#98FB98	(152,251,152)
dark sea green	#8FBC8F	(143,188,143)
medium spring green	#00FA9A	(0,250,154)
spring green	#00FF7F	(0,255,127)
sea green	#2E8B57	(46,139,87)
medium aqua marine	#66CDAA	(102,205,170)
medium sea green	#3CB371	(60,179,113)
light sea green	#20B2AA	(32,178,170)
dark slate gray	#2F4F4F	(47,79,79)
teal	#008080	(0,128,128)
dark cyan	#008B8B	(0,139,139)
aqua	#00FFFF	(0,255,255)
cyan	#00FFFF	(0,255,255)
light cyan	#E0FFFF	(224,255,255)
dark turquoise	#00CED1	(0,206,209)
turquoise	#40E0D0	(64,224,208)
medium turquoise	#48D1CC	(72,209,204)
pale turquoise	#AFEEEE	(175,238,238)
aqua marine	#7FFFD4	(127,255,212)
powder blue	#B0E0E6	(176,224,230)
cadet blue	#5F9EA0	(95,158,160)
steel blue	#4682B4	(70,130,180)
corn flower blue	#6495ED	(100,149,237)
deep sky blue	#00BFFF	(0,191,255)
dodger blue	#1E90FF	(30,144,255)
light blue	#ADD8E6	(173,216,230)
sky blue	#87CEEB	(135,206,235)
light sky blue	#87CEFA	(135,206,250)
midnight blue	#191970	(25,25,112)
navy	#000080	(0,0,128)
dark blue	#00008B	(0,0,139)
medium blue	#0000CD	(0,0,205)
blue	#0000FF	(0,0,255)
royal blue	#4169E1	(65,105,225)
blue violet	#8A2BE2	(138,43,226)
indigo	#4B0082	(75,0,130)
dark slate blue	#483D8B	(72,61,139)
slate blue	#6A5ACD	(106,90,205)
medium slate blue	#7B68EE	(123,104,238)
medium purple	#9370DB	(147,112,219)
dark magenta	#8B008B	(139,0,139)
dark violet	#9400D3	(148,0,211)
dark orchid	#9932CC	(153,50,204)
medium orchid	#BA55D3	(186,85,211)
purple	#800080	(128,0,128)
thistle	#D8BFD8	(216,191,216)
plum	#DDA0DD	(221,160,221)
violet	#EE82EE	(238,130,238)
magenta / fuchsia	#FF00FF	(255,0,255)
orchid	#DA70D6	(218,112,214)
medium violet red	#C71585	(199,21,133)
pale violet red	#DB7093	(219,112,147)
deep pink	#FF1493	(255,20,147)
hot pink	#FF69B4	(255,105,180)
light pink	#FFB6C1	(255,182,193)
pink	#FFC0CB	(255,192,203)
antique white	#FAEBD7	(250,235,215)
beige	#F5F5DC	(245,245,220)
bisque	#FFE4C4	(255,228,196)
blanched almond	#FFEBCD	(255,235,205)
wheat	#F5DEB3	(245,222,179)
corn silk	#FFF8DC	(255,248,220)
lemon chiffon	#FFFACD	(255,250,205)
light golden rod yellow	#FAFAD2	(250,250,210)
light yellow	#FFFFE0	(255,255,224)
saddle brown	#8B4513	(139,69,19)
sienna	#A0522D	(160,82,45)
chocolate	#D2691E	(210,105,30)
peru	#CD853F	(205,133,63)
sandy brown	#F4A460	(244,164,96)
burly wood	#DEB887	(222,184,135)
tan	#D2B48C	(210,180,140)
rosy brown	#BC8F8F	(188,143,143)
moccasin	#FFE4B5	(255,228,181)
navajo white	#FFDEAD	(255,222,173)
peach puff	#FFDAB9	(255,218,185)
misty rose	#FFE4E1	(255,228,225)
lavender blush	#FFF0F5	(255,240,245)
linen	#FAF0E6	(250,240,230)
old lace	#FDF5E6	(253,245,230)
papaya whip	#FFEFD5	(255,239,213)
sea shell	#FFF5EE	(255,245,238)
mint cream	#F5FFFA	(245,255,250)
slate gray	#708090	(112,128,144)
light slate gray	#778899	(119,136,153)
light steel blue	#B0C4DE	(176,196,222)
lavender	#E6E6FA	(230,230,250)
floral white	#FFFAF0	(255,250,240)
alice blue	#F0F8FF	(240,248,255)
ghost white	#F8F8FF	(248,248,255)
honeydew	#F0FFF0	(240,255,240)
ivory	#FFFFF0	(255,255,240)
azure	#F0FFFF	(240,255,255)
snow	#FFFAFA	(255,250,250)
black	#000000	(0,0,0)
dim gray / dim grey	#696969	(105,105,105)
gray / grey	#808080	(128,128,128)
dark gray / dark grey	#A9A9A9	(169,169,169)
silver	#C0C0C0	(192,192,192)
light gray / light grey	#D3D3D3	(211,211,211)
gainsboro	#DCDCDC	(220,220,220)
white smoke	#F5F5F5	(245,245,245)
white	#FFFFFF	(255,255,255)

How to Sum the Two Lowest Positive Integers in C++

Tue, 07 Jun 2022 00:05:00 +0000

The challenge

Create a function that returns the sum of the two lowest positive numbers given an array of minimum 4 positive integers. No floats or non-positive integers will be passed.

For example, when an array is passed like [19, 5, 42, 2, 77], the output should be 7.

[10, 343445353, 3453445, 3453545353453] should return 3453455.

The solution in C++

Option 1:

#include <algorithm>
#include <vector>

long sumTwoSmallestNumbers(std::vector<int> numbers) {
    std::sort(numbers.begin(), numbers.end());
    return (long)numbers[0] + (long)numbers[1];
}

Option 2:

How to Sort an Array of Objects by Property in Javascript

Mon, 06 Jun 2022 00:05:00 +0000

If you need to sort an array of objects by their property values using Javascript, then you don’t need to look further than the built-in sort functionality.

Step 1 – Create an array of objects to work with

let people = [
    {
        name : "John",
        surname : "Doe",
        age : 21
    }, {
        name : "Jack",
        surname : "Bennington",
        age : 35
    }, {
        name : "Jane",
        surname : "Doe",
        age : 19
    }
];

Step 2 – Sort by keys

Option 1 – Sort by surname

people.sort((a, b) => a.surname.localeCompare(b.surname));
console.log(people);

This will give you the following output:

How to create a Countdown Timer in Python

Sun, 05 Jun 2022 00:05:00 +0000

If you need to count down a specific amount of time, say for example, when a token is set to expire, then a countdown timer will be useful.

Step 1 – Writing the Python code

Place the following Python code in a file called countdowntimer.py

Option 1 – Text output

import time

def countdown(t):
  while t:
    mins, secs = divmod(t, 60)
    timer = '{:02d}:{:02d}'.format(mins, secs)
    print(timer, end="\r")
    time.sleep(1)
    t -= 1

  print('Countdown time has elapsed!!')

t = input("Enter the time in seconds: ")

countdown(int(t))

Option 2 – Text and speech output

Here we also invoke say which speaks out the text. This is only native to some operating systems.

How to Remove a Resource from Terraform State

Sat, 04 Jun 2022 00:05:00 +0000

Terraform state reflects the most up to date reference of the infrastructure.

Sometimes you may need to remove a resource from the Terraform state manually. This is helpful if a resource has been deleted or modified manually and the resource definition has been removed in your Terraform code. This way you can re-run your Terraform plan and apply without deleting the remote infra resource that you removed from the state.

How to Delete a Specific Resource in Terraform

Fri, 03 Jun 2022 00:05:00 +0000

Running terraform destroy will tear down the whole stack associated to some terraform code.

However, sometimes you might only want to remove a specific piece of your infrastructure.

To do this, you can use the terraform destroy -target object.

Step 1 – List the State

Get a list of all the resources from the state:

terraform state list

#data.aws_ami.webserver_ami
#aws_autoscaling_group.asg-web[0]
#random_string.rand3
#...

Step 2 – Remove a Specific Resource

Run a terraform destroy -target and pass a resource from the state list above:

How to Create a DynamoDB Lock Table for Terraform

Thu, 02 Jun 2022 00:05:00 +0000

Provision the DynamoDB Table

resource "aws_dynamodb_table" "dynamodb-terraform-state-lock" {
  name = "terraform-state-lock-dynamo"
  hash_key = "LockID"
  read_capacity = 20
  write_capacity = 20
 
  attribute {
    name = "LockID"
    type = "S"
  }
}

Configure the DynamoDB table in Terraform Backend

terraform {
  backend "s3" {
    encrypt = true
    bucket = "your-unique-bucket-name"
    dynamodb_table = "terraform-state-lock-dynamo"
    key    = "terraform.tfstate"
    region = "us-east-1"
  }
}

How to add Comments in Terraform

Wed, 01 Jun 2022 00:05:00 +0000

Terraform, a powerful Infrastructure as Code (IaC) tool, allows you to define and provision infrastructure resources. Properly commenting your Terraform code is essential for maintaining readability and sharing insights with your team. In this comprehensive guide, we’ll explore various methods to add comments in Terraform and address common questions related to Terraform syntax and best practices.

Adding Comments in Terraform

1. # - Single Line Comment

The # symbol marks the beginning of a single-line comment in Terraform. Anything following # on the same line is considered a comment.

How to log/debug in Terraform

Tue, 31 May 2022 00:05:00 +0000

If you have Terraform reporting an error but want more information, then you can configure debug logging.

How to configure Bash

export TF_LOG="TRACE"
export TF_LOG_PATH="terraform.txt"

How to configure PowerShell

$env:TF_LOG="TRACE"
$env:TF_LOG_PATH="terraform.txt"

How to find the number of trailing zeros of N in Rust

Mon, 30 May 2022 00:05:00 +0000

The challenge

Write a program that will calculate the number of trailing zeros in a factorial of a given number.

N! = 1 * 2 * 3 * ... * N

Be careful 1000! has 2568 digits…

For more info, see: http://mathworld.wolfram.com/Factorial.html

Examples

zeros(6) = 1
# 6! = 1 * 2 * 3 * 4 * 5 * 6 = 720 --> 1 trailing zero

zeros(12) = 2
# 12! = 479001600 --> 2 trailing zeros

The solution in Rust

Option 1:

How to do RGB To Hex Conversion in Rust

Sun, 29 May 2022 00:05:00 +0000

The challenge

The rgb function is incomplete. Complete it so that passing in RGB decimal values will result in a hexadecimal representation being returned. Valid decimal values for RGB are 0 – 255. Any values that fall out of that range must be rounded to the closest valid value.

Note: Your answer should always be 6 characters long, the shorthand with 3 will not work here.

The following are examples of expected output values:

How to Rename a Git Branch

Sat, 28 May 2022 00:05:00 +0000

If you want to rename a git branch, then you have a few options, dependent on the use-case.

Option 1 – Rename a Git Branch

git branch -a <oldname> <newname>

Option 2 – Rename the Current Branch

git branch -m <newname>

Option 3 – On Windows

Windows required a capital “-M” instead.

git branch -M <newname>

Push the Local Branch and Reset the Upstream Branch

git push origin -u <newname>

Delete the Old Remote Branch

git push origin --delete <oldname>

How to Find the Shortest Word in C++

Fri, 27 May 2022 00:05:00 +0000

The challenge

Simple, given a string of words, return the length of the shortest word(s).

The string will never be empty and you do not need to account for different data types.

The solution in C++

Option 1:

int find_short(const std::string &str) {
    std::istringstream inp(str);
    std::string s;
    int len = -1;
    while (std::getline(inp, s, ' '))
        if (s.length() < len)
            len = s.length();
    return len;
}

Option 2:

int find_short(std::string str) {
    std::istringstream iss(str);
    std::vector<std::string> vec{ std::istream_iterator<std::string>(iss), {} };
    return std::min_element(vec.begin(), vec.end(), [](const std::string& s1, const std::string& s2) { return s1.length() < s2.length(); })->length();
}

Option 3:

How to Square Every Digit in C++

Thu, 26 May 2022 00:05:00 +0000

The challenge

You are asked to square every digit of a number and concatenate them.

For example, if we run 9119 through the function, 811181 will come out, because 92 is 81 and 12 is 1.

Note: The function accepts an integer and returns an integer

The solution in C++

Option 1:

int square_digits(int n) {
  int a = 1;
  int m = 0;
  while (n > 0) {
    int d = n % 10;
    m += a * d * d;
    a *= d <= 3 ? 10 : 100;
    n /= 10;
  }
  return m;
}

Option 2:

How to Count Vowels in C++

Wed, 25 May 2022 00:05:00 +0000

The challenge

Return the number (count) of vowels in the given string.

We will consider a, e, i, o, u as vowels for this challenge (but not y).

The input string will only consist of lower case letters and/or spaces.

The solution in C++

Option 1:

#include <string>

using namespace std;

bool is_vowel(char c) {
  return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
}

int getCount(const string& inputStr) {
  return count_if(inputStr.begin(), inputStr.end(), is_vowel);
}

Option 2:

How to Calculate the Sum of the Numbers in the Nth row of a Triangle in Golang

Tue, 24 May 2022 00:05:00 +0000

The challenge

Given the triangle of consecutive odd numbers:

             1
          3     5
       7     9    11
   13    15    17    19
21    23    25    27    29
...

Calculate the sum of the numbers in the nth row of this triangle (starting at index 1) e.g.: (Input –> Output)

1 -->  1
2 --> 3 + 5 = 8

The solution in Golang

Option 1:

package solution

func RowSumOddNumbers(n int) int {
    return n * n * n
}

Option 2:

[Solved] Terraform Error accessing remote module registry in PowerShell

Mon, 23 May 2022 00:05:00 +0000

If you are using PowerShell and trying to run a terraform init, you may get an error as follows:

Error: error accessing remote module registry

Failed to retrieve available versions for module ... from registry.terraform.io: Failed to request discovery document: Get "https://registry.terraform.io/.well-known/terraform.json": read tcp x.x.x.x:xxxx->x.x.x.x: wsarecv: An existing connection was forcibly closed by the remote host..

Note that you will still be able to make a successful curl request, but terraform will fail!

How to Recursively Delete a Directory in PowerShell

Sun, 22 May 2022 00:05:00 +0000

If you want to recursively delete a directory/folder using PowerShell, then you have 2 options.

Option 1 – With `LiteralPath` and `Force`

Remove-Item -LiteralPath "myFolder" -Force -Recurse

Option 2 – With implicit and `Recurse`

Remove-Item myFolder/* -Recurse

[Solved] npm ERR! could not determine executable to run

Sat, 21 May 2022 00:05:00 +0000

If you get the following message, then there’s a very easy fix:
npm ERR! could not determine executable to run

The solution – using `npm`

rm -rf .git/hooks
npm install

The solution – using `yarn`

rm -rf .git/hooks
yarn install

[Solved] npm ERR! path node_modules/node-sass

Fri, 20 May 2022 00:05:00 +0000

If you get the following error and need a solution, then look no further!

npm ERR! code 1
npm ERR! path ./node_modules/node-sass
npm ERR! command failed
npm ERR! command sh -c node scripts/build.js

npm ERR! gyp verb cli   './node_modules/node-gyp/bin/node-gyp.js',
npm ERR! gyp verb cli   'rebuild',
npm ERR! gyp verb cli   '--verbose',

Option 1 – With `npm`

First, remove the node-sass dependency from your package.json, then:

npm install
npm i sass
npm start

Option 2 – With `yarn`

First, remove the node-sass dependency from your package.json, then:

How to Install Lodash through Yarn for React

Thu, 19 May 2022 00:05:00 +0000

You can install lodash through yarn as follows:

Step 1 – Install Lodash to get the Library

yarn add lodash

Step 2 – Get the Typescript info

yarn add --dev @types/lodash

How to SHA256 a String in Golang

Wed, 18 May 2022 00:05:00 +0000

If you need to SHA256 a String in Go, then you can use the crypto/sha256 package.

SHA256 a String in Go

package main

import (
	"crypto/sha256"
	"fmt"
)

func main() {
	s := "A sample string to SHA256!"

	h := sha256.New()

	h.Write([]byte(s))

	bs := h.Sum(nil)

	fmt.Println(s)
	fmt.Printf("%x\n", bs)
}

The output will look like this:

A sample string to SHA256!
9abf637c7e39cc4ef84d6d92cf7ffe168dc922b8ae666260d907e0353865ce89

How to Base64 Encode/Decode in Golang

Tue, 17 May 2022 00:05:00 +0000

Go ships with an encoding/base64 package that allows for encode and decoding of Base64 strings.

Import the base64 package and then start using it!

Base64 encode/decode a string

package main

import (
	b64 "encoding/base64"
	"fmt"
)

func main() {
	// define a string
	data := "This is a test string!"

	// Encode to Base64
	sEnc := b64.StdEncoding.EncodeToString([]byte(data))
	fmt.Println(sEnc)

	// Decode from Base64
	sDec, _ := b64.StdEncoding.DecodeString(sEnc)
	fmt.Println(string(sDec))

	// URL Encode
	uEnc := b64.URLEncoding.EncodeToString([]byte(data))
	fmt.Println(uEnc)

	// URL Decode
	uDec, _ := b64.URLEncoding.DecodeString(uEnc)
	fmt.Println(string(uDec))
}

How to Base64 Encode a String in Java

Mon, 16 May 2022 00:05:00 +0000

Quick solution

In short, you can just do this:

new String(Base64.getEncoder().encode(bytes));

Examples and an explanation

In Java 8 and above, you just need to import the Base64 class:

import java.util.Base64;

Then use the Base64 static methods as follows:

byte[] encodedBytes = Base64.getEncoder().encode("Test".getBytes());
System.out.println("encodedBytes " + new String(encodedBytes));

byte[] decodedBytes = Base64.getDecoder().decode(encodedBytes);
System.out.println("decodedBytes " + new String(decodedBytes));

If you want to directly encode a string and get the result as an encoded string:

String encodeBytes = Base64.getEncoder()
    .encodeToString(("Your String").getBytes());

How to add a Lambda Environment Variable in Terraform

Sun, 15 May 2022 00:05:00 +0000

If you have an aws_lambda_function block that needs to make use of environment variables, then you can simply do the following:

resource "aws_lambda_function" "test_lambda" {
  filename         = "lambda_function_payload.zip"
  function_name    = "lambda_function_name"
  runtime          = "python3.9"
  ...

  environment {
    variables = {
      api_key = "secret-key"
    }
  }
}

The above example creates an environment variable called api_key with a value of secret-key

How to perform Array Element Parity in Golang

Sat, 14 May 2022 00:05:00 +0000

The challenge

You will be given an array of integers whose elements have both a negative and a positive value, except for one integer that is either only negative or only positive. Your task will be to find that integer.

Examples:

[1, -1, 2, -2, 3] => 3

3 has no matching negative appearance

[-3, 1, 2, 3, -1, -4, -2] => -4

-4 has no matching positive appearance

[1, -1, 2, -2, 3, 3] => 3

How to Reverse Letters in Kotlin

Fri, 13 May 2022 00:05:00 +0000

The challenge

Given a string str, reverse it omitting all non-alphabetic characters.

For str = "krishan", the output should be "nahsirk".

For str = "ultr53o?n", the output should be "nortlu".

[input] string str

A string consists of lowercase Latin letters, digits, and symbols.

[output] a string

The solution in Kotlin

Option 1:

fun reverseLetter(str: String): String {
    return str.filter(Char::isLetter).reversed()
}

Option 2:

How to Get the ASCII Value of Character in Kotlin

Thu, 12 May 2022 00:05:00 +0000

The challenge

Get the ASCII value of a character.

The solution in Kotlin

Option 1:

val getAscii = Char::toInt

Option 2:

fun getAscii(c: Char) = c.code

Option 3:

fun getAscii(c: Char): Int {
    return c.code.toByte().toInt()
}

Test cases to validate our solution

import kotlin.test.assertEquals
import org.junit.Test

class TestExample {
  @Test
  fun `Basic tests`() {
    assertEquals(65, getAscii('A'))
    assertEquals(32, getAscii(' '))
    assertEquals(33, getAscii('!'))
  }
}

How to update each dependency in package.json to the latest version

Wed, 11 May 2022 00:05:00 +0000

You have 2 options:

Option 1 – Recommended (Using `npx`)

npx npm-check-updates -u
npm install

Option 2 – Older way (Using `npm globally`)

npm i -g npm-check-updates
ncu -u
npm install

How to Convert IPv4 to int32 in Javascript

Tue, 10 May 2022 00:05:00 +0000

The challenge

Take the following IPv4 address: 128.32.10.1 This address has 4 octets where each octet is a single byte (or 8 bits).

1st octet 128 has the binary representation: 10000000
2nd octet 32 has the binary representation: 00100000
3rd octet 10 has the binary representation: 00001010
4th octet 1 has the binary representation: 00000001

So 128.32.10.1 == 10000000.00100000.00001010.00000001

Because the above IP address has 32 bits, we can represent it as the 32 bit number: 2149583361.

How to Solve the Grouped by Commas Challenge in Javascript

Mon, 09 May 2022 00:05:00 +0000

The challenge

Finish the solution so that it takes an input n (integer) and returns a string that is the decimal representation of the number grouped by commas after every 3 digits.

Assume: 0 <= n < 2147483647

       1  ->           "1"
      10  ->          "10"
     100  ->         "100"
    1000  ->       "1,000"
   10000  ->      "10,000"
  100000  ->     "100,000"
 1000000  ->   "1,000,000"
35235235  ->  "35,235,235"

The solution in Javascript

Option 1:

How to Save sed Output Directly to a File

Sun, 08 May 2022 00:05:00 +0000

You have 3 options here:

Option 1: use `tee` with sed

sed 's/Hello/Hi/g' file-name | tee file

Option 2: use `>` with sed

sed 's/Hello/Hi/g' file-name > file

Option 3: use `sed` with `-i` option

sed -i 's/Hello/Hi/g' file-name

How to Convert BigNumber to Int/Number in Ethers/Web3

Sat, 07 May 2022 00:05:00 +0000

If you have a BigNumber when using web3, then you can convert this to a regular Javascript Number using the ethers library as follows:

ethers.BigNumber.from(max).toNumber()

<a href="https://github.com/ethers-io/ethers.js/" target="_blank" rel="noreferrer noopener nofollow">Ethers</a> is a complete Ethereum library and wallet implementation in Javascript.

How to Create a Pyramid Array in Javascript

Fri, 06 May 2022 00:05:00 +0000

The challenge

Write a function that when given a number >= 0, returns an Array of ascending length subarrays.

pyramid(0) => [ ]
pyramid(1) => [ [1] ]
pyramid(2) => [ [1], [1, 1] ]
pyramid(3) => [ [1], [1, 1], [1, 1, 1] ]

Note: the subarrays should be filled with 1s

The solution in Javascript

Option 1:

function pyramid(n) {
  const res = [];
  for(let i = 0; i < n; i++){
    res.push([...Array(i+1)].fill(1))
  }
  return res;
}

Option 2:

How to Create a Reverse Polish Notation Calculator in Javascript

Thu, 05 May 2022 00:05:00 +0000

The challenge

Your job is to create a calculator which evaluates expressions in Reverse Polish notation.

For example expression 5 1 2 + 4 * + 3 - (which is equivalent to 5 + ((1 + 2) * 4) - 3 in normal notation) should evaluate to 14.

For your convenience, the input is formatted such that a space is provided between every token.

How to declare a global variable in React?

Wed, 04 May 2022 00:05:00 +0000

If you need to declare a global variable in React, then you can do the following:

Create a file called config.js

module.exports = global.config = {
    something: {
        somethingelse: {
            amount: 123,
            name: "Andrew"
        }
    }
};

Then import the config file where you need it:

import './config';

Then where you need it in your code:

global.config.something.somethingelse.amount

global.config.something.somethingelse.name

How to Find the Missing Term in an Arithmetic Progression in Javascript

Tue, 03 May 2022 00:05:00 +0000

The challenge

An Arithmetic Progression is defined as one in which there is a constant difference between the consecutive terms of a given series of numbers. You are provided with consecutive elements of an Arithmetic Progression. There is however one hitch: exactly one term from the original series is missing from the set of numbers that have been given to you. The rest of the given series is the same as the original AP. Find the missing term.

How to Count Characters in a Javascript String

Mon, 02 May 2022 00:05:00 +0000

The challenge

The main idea is to count all the occurring characters in a string. If you have a string like aba, then the result should be {'a': 2, 'b': 1}.

What if the string is empty? Then the result should be an empty object literal, {}.

The solution in Javascript

Option 1:

function count (string) {  
  var count = {};
  string.split('').forEach(function(s) {
     count[s] ? count[s]++ : count[s] = 1;
  });
  return count;
}

Option 2:

How to Increment/Decrement a value in React/NextJS

Sun, 01 May 2022 00:05:00 +0000

Use the following code block to get started:

function GetCount() {
  const [count, setCount] = useState(1);

  const incrementCounter = () => {
    setCount(count+1)
  }
  const decrementCounter = () => {
    if (count>1) setCount(count-1)
  }

  return <div className="_counterWrapper">
    <span className="_dec" onClick={() => decrementCounter()}>-</span>
    <span className="_val">{count}</span>
    <span className="_inc" onClick={() => incrementCounter()}>+</span>
  </div>
}

Then in your HTML code, add it like this:

<GetCount />

How to disable text selection highlighting in CSS

Sat, 30 Apr 2022 00:05:00 +0000

If you would like to disable the text selection highlighting that is enabled by default on all browsers, then you can do this:

user-select: none;

If you are concerned about cross-browser support, then use this class:

.noselect {
  -webkit-touch-callout: none; /* iOS Safari */
    -webkit-user-select: none; /* Safari */
     -khtml-user-select: none; /* Konqueror HTML */
       -moz-user-select: none; /* Old versions of Firefox */
        -ms-user-select: none; /* Internet Explorer/Edge */
            user-select: none; /* Non-prefixed version, currently
                                  supported by Chrome, Edge, Opera and Firefox */
}

You can then use it like this:

Irreducible Sum of Rationals in Golang

Fri, 29 Apr 2022 00:05:00 +0000

The challenge

You will have a list of rationals in the form:

lst = [ [numer_1, denom_1] , ... , [numer_n, denom_n] ]

where all numbers are positive integers. You have to produce their sum N / D in an irreducible form: this means that N and D have only 1 as a common divisor.

Return the result in the form: "N/D"

If the result is an integer (D evenly divides N) return: "n"

How to copy S3 objects between AWS accounts

Thu, 28 Apr 2022 00:05:00 +0000

In your source account create a customer-managed policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListBucket",
                "s3:GetObject"
            ],
            "Resource": [
                "arn:aws:s3:::source-EXAMPLE-BUCKET",
                "arn:aws:s3:::source-EXAMPLE-BUCKET/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListBucket",
                "s3:PutObject",
                "s3:PutObjectAcl"
            ],
            "Resource": [
                "arn:aws:s3:::destination-EXAMPLE-BUCKET",
                "arn:aws:s3:::destination-EXAMPLE-BUCKET/*"
            ]
        }
    ]
}

In your destination bucket, update the bucket policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::1234567890:user/Andrew"
            },
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::destination-EXAMPLE-BUCKET/*",
            "Condition": {
                "StringEquals": {
                    "s3:x-amz-acl": "bucket-owner-full-control"
                }
            }
        },
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::1234567890:user/Andrew"
            },
            "Action": "s3:ListBucket",
            "Resource": "arn:aws:s3:::destination-EXAMPLE-BUCKET"
        }
    ]
}

Testing the S3 copy between accounts:

How to find all symlinks in a directory tree on Mac

Wed, 27 Apr 2022 00:05:00 +0000

If you need to recursively find all symbolic links in a directory tree on a Mac, then you have a couple of options.

You could be trying to find them because a tool like Dropbox is consuming high CPU and you need to remove them, or perhaps you want to move a directory to another machine or network drive and verifying a package is required.

Option 1 – View all files that are symlinks

ls -lR . | grep ^l

Option 2 – View all symlink-files as absolute paths

find . -type l -ls

How to Install App Mesh on AWS EKS

Tue, 26 Apr 2022 00:05:00 +0000

You can follow the steps below to install App Mesh on AWS EKS (Kubernetes).

Step 1 – Prerequisites

curl -o pre_upgrade_check.sh https://raw.githubusercontent.com/aws/eks-charts/master/stable/appmesh-controller/upgrade/pre_upgrade_check.sh
sh ./pre_upgrade_check.sh

Step 2 – Add Helm Repo

helm repo add eks https://aws.github.io/eks-charts

Step 3 – Add Custom Resource Definitions (CRDs)

kubectl apply -k "https://github.com/aws/eks-charts/stable/appmesh-controller/crds?ref=master"

Step 4 – Create a Namespace for App Mesh

kubectl create ns appmesh-system

Step 5 – Set Environment Variables

You will need to set a couple of environment variables to make things easier later.

[Solved] Kubernetes Namespace stuck in Terminating state

Mon, 25 Apr 2022 00:05:00 +0000

If you have tried to delete a Kubernetes namespace, and it has been hanging in ‘deleting’ for hours on end, it’s likely that you have dangling resources that have not deleted yet.

$ kubectl get ns
NAME              STATUS        AGE
apps              Active        2d19h
default           Active        3d8h
my-apps           Terminating   11h

This will prevent the namespace from being removed.

How to find resources that need to be deleted

You can chain the api-resources verbs along with a kubectl get to find dangling resources:

[Solved] Error creating: pods “my-service-a-xxx” is forbidden: error looking up service account my-apps/my-service-a: serviceaccount “my-service-a” not found

Sun, 24 Apr 2022 00:05:00 +0000

So you’ve run a deployment and tried to check the pods and there’s nothing there!

kubectl get pods

Next step is to see what’s happening with the replicaset

kubectl get rs

Then take the replicaset name and do a describe on it:

kubectl describe rs my-service-a-5549cbc6c8

The error

Events:
  Type     Reason            Age           From         Message
  ----     ------            ----          ----         -------
  Warning  FailedCreate      2m10s..  replicaset-controller  Error creating: pods "my-service-a-5549cbc6c8-" is forbidden: error looking up service account my-apps/my-service-a: serviceaccount "my-service-a" not found

It’s down to a missing Service Account!

[Solved] error: src refspec main does not match any

Sat, 23 Apr 2022 00:05:00 +0000

If you get the following error:

error: src refspec main does not match any
error: failed to push some refs to 'https://github.com/ao/xxx.git'

This is because you probably haven’t committed any files to git yet!

Fix for: `src refspec main does not match any`

Make sure to add your files, if they have not been added yet:

git add .

Commit your files:

git commit -m "your commit message"

Push your changes to the git repo, remember to swap out the branch name as appropriate:

How to Force a Redeploy in Kubernetes

Fri, 22 Apr 2022 00:05:00 +0000

If you need to force a redeploy of a deployment in Kubernetes, then you can use the rollout feature.

You may have an image that has been updated, but without changing the tag/version.

Step 1 – Optionally update the `imagePullPolicy`

If you have not changed the image version, then check your imagePullPolicy.

In your deployment.yaml file:

containers:
  - name: backend
    image: aoms/mock_backend_python:latest
    imagePullPolicy: Always

Step 2 – Get the deployment name

kubectl get deploy

Step 3 – Force the Redeployment

kubectl rollout restart deploy backend

How to Print to stdout in Flask using Python

Thu, 21 Apr 2022 00:05:00 +0000

If you are trying to print() to the console/stdout in your Flask app, but nothing is happening, then you just need to flush your prints, as follows:

print('This will print', flush=True)

How to Restart a Deployment in Kubernetes

Wed, 20 Apr 2022 00:05:00 +0000

If you need to restart a deployment in Kubernetes, perhaps because you would like to force a cycle of pods, then you can do the following:

Step 1 – Get the deployment name

kubectl get deployment

Step 2 – Restart the deployment

kubectl rollout restart deployment <deployment_name>

How to push multiple Dockerfile apps to AWS ECR at the same time

Tue, 19 Apr 2022 00:05:00 +0000

I have a parent directory containing multiple sub-directories. Each of these child directories is a different application and contains a Dockerfile.

I want to build and push each image to AWS ECR.

The directory looks as follows:

├── apps
    ├── microservice1
        ├── app.js
        ├── Dockerfile
        ├── package.json
        └── readiness.txt
    ├── frontend
        ├── Dockerfile
        ├── index.html
        ├── package.json
        ├── server.js
    ├── microservice2
        ├── app.py
        ├── bootstrap.sh
        ├── Dockerfile
        └── requirements.txt

Notice there are 3 apps, each with their own Dockerfile, under the parent apps directory.

How to Create a Horizontal Pod Autoscaler in Kubernetes

Mon, 18 Apr 2022 00:05:00 +0000

If you could like to a create a Horizontal Pod Autoscaler (hpa) in Kubernetes, then you could run the following:

Step 1 – Create a Deployment

If you already have a deployment, then ignore this step, otherwise:

kubectl create deployment php-apache --image=us.gcr.io/k8s-artifacts-prod/hpa-example
kubectl set resources deploy php-apache --requests=cpu=200m
kubectl expose deploy php-apache --port 80

kubectl get pod -l app=php-apache

Step 2 – Create a Horizontal Pod Autoscaler

kubectl autoscale deployment php-apache `#The target average CPU utilization` \
    --cpu-percent=50 \
    --min=1 `#The lower limit for the number of pods that can be set by the autoscaler` \
    --max=10 `#The upper limit for the number of pods that can be set by the autoscaler`

Step 3 – Get your `hpa`

kubectl get hpa

How to Run a Load Generator on Kubernetes

Sun, 17 Apr 2022 00:05:00 +0000

If you would like to test hpa, Horizontal Pod Autoscaling, or throw some chaos at a specific deployment in Kubernetes, then you could run a Load Generator

Step 1 – Run a BusyBox container

The following command will use a busybox container and dump you into it’s shell window:

kubectl run -i --tty load-generator --image=busybox /bin/sh

As an alternative, you could also run:

kubectl --generator=run-pod/v1 run -i --tty load-generator --image=busybox /bin/sh

Step 2 – Run a `wget` loop

You can now trigger a wget loop to make HTTP request calls to your deployment:

How to Deploy a Metrics Server in Kubernetes

Sat, 16 Apr 2022 00:05:00 +0000

If you would like to deploy a Metrics Server in Kubernetes, then you first need to create a namespace for it to live it, followed by installing the actual metrics server.

Step 1 – Install the Metrics Server

Using kubectl

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/download/v0.5.0/components.yaml

Using helm

kubectl create namespace metrics

helm install metrics-server \
    stable/metrics-server \
    --version 2.9.0 \
    --namepsace metrics

Step 2 – Get the Metrics Server Status

If you used kubectl above, then you should be able to run:

How to create an AWS EKS cluster using eksctl

Fri, 15 Apr 2022 00:05:00 +0000

eksctl dramatically simplifies the creation of AWS EKS clusters, by providing a simple command-line interface.

Step 1 – Define a Cluster YAML

You can either create a file called ekscluster.yaml and place the YAML in, or run the following command which will create a file called ekscluster.yaml and automatically add the default YAML configuration for you.

cat << EOF > ekscluster.yaml
---
apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: eksworkshop-eksctl
  region: ${AWS_REGION}
  version: "1.19"

availabilityZones: ["${AZS[0]}", "${AZS[1]}", "${AZS[2]}"]

managedNodeGroups:
- name: nodegroup
  desiredCapacity: 3
  instanceType: t3.small
  ssh:
    enableSsm: true

# To enable all of the control plane logs, uncomment below:
# cloudWatch:
#  clusterLogging:
#    enableTypes: ["*"]

secretsEncryption:
  keyARN: ${MASTER_ARN}
EOF

Step 2 – Create the EKS Cluster

Tell the eksctl tool to create a new cluster using the ekscluster.yaml.

How to Dockerize a Flask App

Thu, 14 Apr 2022 00:05:00 +0000

If you have a Flask app that you would like packaged in a Docker container, then you can do the following. The steps outlined below will help you create the following directory tree:

└── flaskapp
        ├── Dockerfile
        ├── app.py
        └── requirements.txt

Step 1 – Create your Flask app

In a new directory, create the following files:

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_geek():
  return '<h1>Hello world!</h2>'

if __name__ == "__main__":
  app.run(debug=True)

requirements.txt

How to get an EKS Cluster name from an AWS Region

Wed, 13 Apr 2022 00:05:00 +0000

You can use the aws cli to get the EKS cluster name, parse the first result and return it into a variable.

EKS_CLUSTER_NAME=$(aws eks list-clusters --region us-west-2 --query clusters[0] --output text)
echo $EKS_CLUSTER_NAME

How to automatically generate a Manifests file in Kubernetes

Tue, 12 Apr 2022 00:05:00 +0000

If you want to automatically generate a manifest file in Kubernetes, you can do so by using the kubectl run command coupled with a --dry-run to output directly to yaml.

kubectl run nginx --image=nginx --port=80 --replicas=2 --expose --dry-run -o yaml

You can also output this directly to a file on disk as follows:

kubectl run nginx --image=nginx --port=80 --replicas=2 --expose --dry-run -o yaml > your-deployment-manifest.yaml

How to Sort Pods by CreationTimestamp in Kubernetes

Mon, 11 Apr 2022 00:05:00 +0000

If you need to sort a list of your pods by their CreationTimestamp, then do the following:

kubectl get pods -n kube-system --sort-by=metadata.creationTimestamp

A better way to specify the JSON path is:

kubectl get pods -n kube-system --sort-by='{.metadata.creationTimestamp}'

How to Jump onto a Kubernetes Pod with Bash

Sun, 10 Apr 2022 00:05:00 +0000

If you want to jump onto a particular Kubernetes Pod and run Bash within it, you can do so as follows:

kubectl exec -ti <pod_name> /bin/bash

You can get the <pod_name> by running kubectl get pods

How to run Shell Commands in a Kubernetes Cluster

Sat, 09 Apr 2022 00:05:00 +0000

If you would like to run shell commands inside of your Kubernetes cluster, then you can use the kubectl run command.

What the syntax looks like

kubectl run --image=<imagename> <name> -restart=Never -it --rm -- /bin/sh -c "<command>"

Breaking this down, you pass in an imagename which is the container image you would like to execute the commands in, the name of this temporary container, and then command you would like to run in it.

How to Bulk Move All Email from One Account to Another using the CLI

Fri, 08 Apr 2022 00:05:00 +0000

If you find yourself in a position where you need to sync all emails from one account to another, then you can use the imapsync command-line tool to bulk copy, or move everything for you.

Step 1 – Get `imapsync`

You need to get the imapsync tool running locally.

It can be found here https://github.com/imapsync/imapsync

Alternatively, if you are using a Mac and have homebrew installed, then you’re in luck!

How to Install AWS CLI on Linux

Thu, 07 Apr 2022 00:05:00 +0000

You can download and install the AWS CLI on Linux as follows:

Perform the install

curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2.zip"
unzip awscliv2.zip
sudo ./aws/install

Verify the install

aws --version

How to Reboot Networking on Mac from CLI

Wed, 06 Apr 2022 00:05:00 +0000

If you need to reboot, or restart the networking interface on your Mac, by using the CLI, then you can issue the following commands:

Using the `ifconfig` primary interface

Tear down the networking interface

sudo ifconfig en0 down

Restart the networking interface

sudo ifconfig en0 up

Verify the networking restart

ifconfig -u en0

Alternative without `sudo`, using `networksetup`

If you need to perform the same result, but not able to run sudo, then look to the networksetup.

[Solved] fatal: unable to access : SSL certificate problem: self signed certificate in certificate chain

Tue, 05 Apr 2022 00:05:00 +0000

If you get the following error:

fatal: unable to access <git>: SSL certificate problem: self signed certificate in certificate chain

..when trying to clone a git repo, then you can quickly get around it by doing one of the following.

Note that both of these solutions are merely workarounds and should be done at absolute worst case.

Workaround Solution 1

Disable SSL verification while running the git clone.

git -c http.sslVerify=false clone <repository-name>

Workaround Solution 2

Disable SSL verification globally while running the git clone.

How to Extract the Files in a Docker Image

Mon, 04 Apr 2022 00:05:00 +0000

Ever needed to extract the files in a Docker container?

Docker provides the save sub-command.

Exporting Docker files into a Tar Archive

The examples below use a Docker container called: aoms/hellojava

Swap this out with your own container as required.

docker save aoms/hellojava > hellojava.tar

hellojava.tar now contains a list of files found in the Docker image.

Taking it one step further

You can make this a bit better by extracting it into a new directory and untarring automatically:

[Solved] Error response from daemon: No such image: Docker

Sun, 03 Apr 2022 00:05:00 +0000

If you’ve run into this dreaded error:

Error response from daemon: No such image:

Then you can solve it as follows:

Step 1

Perform a docker pull -a <org/image>

Then perform a docker images -a to see what the version is.

Step 2

This issue can occur when it is trying to map tag to latest, but a specific version is explicitly listed instead.

docker tag <org>/<image>:v1 <new_org>/<image>

Make sure to replace :v1 with the specific TAG that was shown from the docker images command above.

How to Bootstrap a Web Server on AWS EC2

Sat, 02 Apr 2022 00:05:00 +0000

When you launch an EC2 instance, you can use the user-data to bootstrap a instance creation script.

We can use the following code to start a web server and echo out it’s instance id:

#!/bin/bash
yum update -y
yum install -y httpd
systemctl start httpd
systemctl enable httpd
echo "<h1>Hello World from $(hostname -f)</h1>" > /var/www/html/index.html

Steps to create a new bootstrapped instance

Step 1 – Launch a new instance

How to Update Kubectl Config from AWS EKS

Fri, 01 Apr 2022 00:05:00 +0000

Ever searched for kubectl update config from aws eks and needed a quick result?

Step 1 – Validate AWS CLI

Make sure that you have valid AWS Credentials setup in your aws cli.

You can check this by typing:

aws sts get-caller-identity

This will let you know where your aws cli is pointing to.

You may need to update your ~/.aws/credentials file with a profile_name, aws_access_key_id, aws_secret_access_key and aws_session_token if these are generated for you by your Single Sign On (SSO).

How to Generate a Random String in Java

Thu, 31 Mar 2022 00:05:00 +0000

Java provides many ways to generate random strings.

1. Using Apache Commons

public void generatingRandomAlphanumericString_ApacheCommons() {
    String generatedString = RandomStringUtils.randomAlphanumeric(10);
    System.out.println(generatedString);
}

2. Using Java 8

public void generatingRandomAlphanumericString_Java8() {
    int leftLimit = 48; // numeral '0'
    int rightLimit = 122; // letter 'z'
    int targetStringLength = 10;
    Random random = new Random();

    String generatedString = random.ints(leftLimit, rightLimit + 1)
      .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
      .limit(targetStringLength)
      .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
      .toString();

    System.out.println(generatedString);
}

3. Using Plain Java

public void generatingRandomStringUnbounded_PlainJava() {
    byte[] array = new byte[7]; // length is bounded by 7
    new Random().nextBytes(array);
    String generatedString = new String(array, Charset.forName("UTF-8"));

    System.out.println(generatedString);
}

How to Generate a Random String in Python

Wed, 30 Mar 2022 00:05:00 +0000

Python gives the ability to generate random strings out of the box, by using a combination of the string and random modules.

import string
import random

# How many characters do you want
S = 10

# Call random.choices() string module to find the string in Uppercase + numeric data.  
ran = ''.join(random.choices(string.ascii_uppercase + string.digits, k = S))    

# Print the result
print("The randomly generated string is : " + str(ran))

How to Generate a Random Number/String in Terraform

Tue, 29 Mar 2022 00:05:00 +0000

If you need to generate a random number or string in Terraform, then you can use the following:

resource "random_id" "myrandom" {
  keepers = {
    first = "${timestamp()}"
  }     
  byte_length = 8
}

Then refer to it as:

random_id.myrandom.hex

[Solved] Unable to connect to the server: dial tcp: lookup with AWS EKS

Mon, 28 Mar 2022 00:05:00 +0000

If you have received the following error while trying to issue commands to kubectl:

Unable to connect to the server: dial tcp: lookup

Then it may be due to your kube-config being out of date. You might just need to update the local kube-config.

How to update the local `kube-config`

Make sure to replace eu-west-1 with your cluster’s region, and replace cluster_name with the name of your EKS cluster.

aws eks --region "eu-west-1" update-kubeconfig --name "cluster_name"

How to update `kube-config` from Terraform state

aws eks --region $(terraform output -raw region) update-kubeconfig --name $(terraform output -raw cluster_name)

The above code makes use of the Terraform state’s output from when you generated the cluster.

How to Store Terraform State in AWS S3

Sun, 27 Mar 2022 00:05:00 +0000

Storing Terraform states files locally is not recommended. Instead you should use a backend such as as S3 from AWS.

To do this, you just need to add the following backend information in a terraform block in your code:

terraform {
  backend "s3" {
    bucket = "mybucket"
    key    = "path/to/my/key"
    region = "eu-west-1"
  }
}

[Solved] ZipArchive extension: disabled/not installed on Ubuntu

Sat, 26 Mar 2022 00:05:00 +0000

If you have come across the following error:

ZipArchive extension: disabled/not installed

This just means that you are missing the php-zip module.

How to fix the ZipArchive extension problem

Run the following command:

sudo apt-get install -y php-zip

Now restart Apache2, and you’re good!

service apache2 restart

Calculating Cartesian Neighbors Distance in Golang

Fri, 25 Mar 2022 00:05:00 +0000

The challenge

We have been searching for all the neighboring points in a Cartesian coordinate system. As we know each point in a coordinate system has eight neighboring points when we search it by range equal to 1, but now we will change the range by the third argument of our function (range is always greater than zero). For example, if range = 2, count of neighboring points = 24. In this challenge, a grid step is the same (= 1).

How to Calculate Dominant Primes in Golang

Thu, 24 Mar 2022 00:05:00 +0000

The challenge

The prime number sequence starts with: 2,3,5,7,11,13,17,19.... Notice that 2 is in position one.

3 occupies position two, which is a prime-numbered position. Similarly, 5, 11 and 17 also occupy prime-numbered positions. We shall call primes such as 3,5,11,17 dominant primes because they occupy prime-numbered positions in the prime number sequence. Let’s call this listA.

As you can see from listA, for the prime range range(0,10), there are only two dominant primes (3 and 5) and the sum of these primes is: 3 + 5 = 8.

[Solved] error: src refspec main does not match

Wed, 23 Mar 2022 00:05:00 +0000

When you first try and push to a git repository, you may get the following error message:

error: src refspec master does not match any.
error: failed to push some refs to 'git@github ... .git'

This is because you have not committed your files!

How to Fix `src refspec main does not match`

git commit -m "initial commit"
git push origin main

The above code will commit your files that are staged, before pushing them to your desired branch.

How to Solve Simple Square Numbers in Golang

Tue, 22 Mar 2022 00:05:00 +0000

The challenge

In this challenge, you will be given a number n (n > 0) and your task will be to return the smallest square number N (N > 0) such that n + N is also a perfect square. If there is no answer, return -1 (nil in Clojure, Nothing in Haskell, None in Rust).

solve 13 = 36
<em>; because 36 is the smallest perfect square that can be added to 13 to form a perfect square => 13 + 36 = 49</em>

solve 3 = 1 <em>; 3 + 1 = 4, a perfect square</em>
solve 12 = 4 <em>; 12 + 4 = 16, a perfect square</em>
solve 9 = 16 
solve 4 = nil

The solution in Golang

Option 1:

How to perform Function Iteration in Golang

Mon, 21 Mar 2022 00:05:00 +0000

The challenge

The purpose of this challenge is to write a higher-order function returning a new function that iterates on a specified function a given number of times. This new function takes in an argument as a seed to start the computation.

For instance, consider the function getDouble. When run twice on value 3, yields 12 as shown below.

getDouble(3) => 6
getDouble(6) => 12

Let us name the new function createIterator and we should be able to obtain the same result using createIterator as shown below:

Determining Integer Depth in Python

Sun, 20 Mar 2022 00:05:00 +0000

The challenge

The depth of an integer n is defined to be how many multiples of n it is necessary to compute before all 10 digits have appeared at least once in some multiple.

Example:

let see n=42

Multiple         value         digits     comment
42*1              42            2,4 
42*2              84             8         4 existed
42*3              126           1,6        2 existed
42*4              168            -         all existed
42*5              210            0         2,1 existed
42*6              252            5         2 existed
42*7              294            9         2,4 existed
42*8              336            3         6 existed 
42*9              378            7         3,8 existed

Looking at the above table under digits column you can find all the digits from `` to 9, Hence it required 9 multiples of 42 to get all the digits. So the depth of 42 is 9. Write a function named computeDepth which computes the depth of its integer argument. Only positive numbers greater than zero will be passed as an input.

How to Reverse a singly-linked list in Python

Sat, 19 Mar 2022 00:05:00 +0000

The challenge

Implement a function reverse_list that takes a singly-linked list of nodes and returns a matching list in the reverse order.

Assume the presence of a class Node, which exposes the property value/Value and next/Next. next must either be set to the next Node in the list, or to None (or null) to indicate the end of the list.

To assist in writing tests, a function make_linked_list (Node.asLinkedList() in Java) has also been defined, which converts a python list to a linked list of Node.

Calculating Simple Time Difference in Python

Fri, 18 Mar 2022 00:05:00 +0000

The challenge

In this challenge, you will be given a series of times at which an alarm goes off. Your task will be to determine the maximum time interval between alarms. Each alarm starts ringing at the beginning of the corresponding minute and rings for exactly one minute. The times in the array are not in chronological order. Ignore duplicate times, if any.

Examples:

# If the alarm goes off now, it will not go off for another 23 hours and 59 minutes.
solve(["14:51"]) = "23:59"

# The max interval that the alarm will not go off is 11 hours and 40 minutes.
solve(["23:00","04:22","18:05","06:24"]) == "11:40"

In the second example, the alarm goes off 4 times in a day.

Calculating Odd/Even number of divisors in Python

Thu, 17 Mar 2022 00:05:00 +0000

The challenge

Given an integer n return "odd" if the number of its divisors is odd. Otherwise, return "even".

Note: big inputs will be tested.

All prime numbers have exactly two divisors (hence "even").

For n = 12 the divisors are [1, 2, 3, 4, 6, 12] – "even".

For n = 4 the divisors are [1, 2, 4] – "odd".

The solution in Python code

Option 1:

Calculate possibilities of throwing a coin N times in Python

Wed, 16 Mar 2022 00:05:00 +0000

The challenge

In this challenge, you will be given an integer n, which is the number of times that is thrown a coin. You will have to return an array of strings for all the possibilities (heads[H] and tails[T]). Examples:

coin(1) should return {"H", "T"}
coin(2) should return {"HH", "HT", "TH", "TT"}
coin(3) should return {"HHH", "HHT", "HTH", "HTT", "THH", "THT", "TTH", "TTT"}

When finished sort them alphabetically.

In C and C++ just return a char* with all elements separated by, (without space):
coin(2) should return "HH,HT,TH,TT"

How to Convert Integer to Whitespace format in Python

Tue, 15 Mar 2022 00:05:00 +0000

The challenge

Hereinafter, [space] refers to " ", [tab] refers to "\t", and [LF] refers to "\n" for illustrative purposes. This does not mean that you can use these placeholders in your solution.

In esoteric language called Whitespace, numbers are represented in the following format:

first character represents the sign: [space] for plus, [tab] for minus;
characters after that and until [LF] are the binary representation of the integer: [space] for 0, [tab] for 1.
characters after that are the binary representation of the absolute value of the number, with [space] for 0, [tab] for 1, the rightmost bit is the least significand bit, and no leading zero bits.
the binary representation is immediately followed by [LF].

Notes

Valid Whitespace number must always have at least two characters: a sign and the terminator. In case there are only two characters, the number is equal to zero.
For the purposes of this challenge, zero must always be represented as [space][LF].
In Whitespace, only space, tabulation and linefeed are meaningful characters. All other characters are ignored. However, for the purposes of this simple challenge, please do not add any other characters in the output.
In this challenge, input will always be a valid negative or positive integer.
For your convenience, in this challenge we will use unbleach() function when evaluating your results. This function replaces whitespace characters with [space], [tab], and [LF] to make fail messages more obvious. You can see how it works in Example Test Cases.

Examples

1 in Whitespace is " \t\n".
`` in Whitespace is " \n".
-1 in Whitespace is "\t\t\n".
2 in Whitespace is " \t \n".
-3 in Whitespace is "\t\t\t\n".

The solution in Python code

Option 1:

How to Perform Frog Jumping in Python

Mon, 14 Mar 2022 00:05:00 +0000

The challenge

You have an array of integers and have a frog at the first position

[Frog, int, int, int, ..., int]

The integer itself may tell you the length and the direction of the jump

For instance:

 2 = jump two indices to the right
-3 = jump three indices to the left
 0 = stay at the same position

Your objective is to find how many jumps are needed to jump out of the array.

How to Calculate the area of a regular N sides polygon inside a circle of radius R in Python

Sun, 13 Mar 2022 00:05:00 +0000

The challenge

Write the following function:

def area_of_polygon_inside_circle(circle_radius, number_of_sides):

It should calculate the area of a regular polygon of numberOfSides, number-of-sides, or number_of_sides sides inside a circle of radius circleRadius, circle-radius, or circle_radius which passes through all the vertices of the polygon (such a circle is called circumscribed circle or circumcircle). The answer should be a number rounded to 3 decimal places.

How to create an Image Host Filename Generator in Python

Sat, 12 Mar 2022 00:05:00 +0000

The challenge

You are developing an image hosting website.

You have to create a function for generating random and unique image filenames.

Create a function for generating a random 6 character string that will be used to access the photo URL.

To make sure the name is not already in use, you are given access to a PhotoManager object.

You can call it like so to make sure the name is unique

How to Find the Missing Alphabets in Python

Fri, 11 Mar 2022 00:05:00 +0000

The challenge

Task

Given string s, which contains only letters from a to z in lowercase.

A set of the alphabet is given by abcdefghijklmnopqrstuvwxyz.

2 sets of alphabets mean 2 or more alphabets.

Your task is to find the missing letter(s). You may need to output them by the order a-z. It is possible that there is more than one missing letter from more than one set of alphabet.

How to move MySQL database to another drive

Thu, 10 Mar 2022 00:05:00 +0000

Step 1:

mysql -u root -p

Find out where the data directory is located:

mysql> select @@datadir;

Output
+-----------------+
| @@datadir       |
+-----------------+
| /var/lib/mysql/ |
+-----------------+
1 row in set (0.00 sec)

Step 2:

Now you can stop the server and check the status:

sudo systemctl stop mysql

sudo systemctl status mysql

It’s time to make a copy to your new mount location:

How to Find the Sum of Prime-Indexed Elements in Go

Wed, 09 Mar 2022 00:05:00 +0000

The challenge

You will be given an integer array and your task is to return the sum of elements occupying prime-numbered indices.

The first element of the array is at index ``.

The solution in Golang

Option 1:

package solution 
import "math/big"
func Solve(arr []int) int {
  c := 0
  for i := 0; i < len(arr); i++ {
    n := arr[i]  
    if big.NewInt(int64(i)).ProbablyPrime(0) {
        c += n     
    }
  }
  return c
}

Option 2:

How to Find the Longest Substring in Alphabetical Order in Python

Tue, 08 Mar 2022 00:05:00 +0000

The challenge

Find the longest substring in alphabetical order.

Example:

the longest alphabetical substring in "asdfaaaabbbbcttavvfffffdf" is "aaaabbbbctt".

Overview:

There are tests with strings up to 10 000 characters long so your code will need to be efficient.

The input will only consist of lowercase characters and will be at least one letter long.

If there are multiple solutions, return the one that appears first.

The solution in Python

Option 1:

Calculate the Most Frequent Weekdays in Go

Mon, 07 Mar 2022 00:05:00 +0000

The challenge

What is your favourite day of the week? Check if it’s the most frequent day of the week in the year.

You are given a year as integer (e. g. 2001). You should return the most frequent day(s) of the week in that year. The result has to be a list of days sorted by the order of days in week (e. g. ['Monday', 'Tuesday'], ['Saturday', 'Sunday'], ['Monday', 'Sunday']). Week starts with Monday.

Return Index of Matching Closing Bracket in Go

Sun, 06 Mar 2022 00:05:00 +0000

The challenge

In this challenge, you will be given a string with brackets and an index of an opening bracket and your task will be to return the index of the matching closing bracket. Both the input and returned index are 0-based. An opening brace will always have a closing brace. Return an error if there is no answer.

solve("((1)23(45))(aB)", 0) = 10 // the opening brace at index 0 matches the closing brace at index 10
solve("((1)23(45))(aB)", 1) = 3 
solve("((1)23(45))(aB)", 2) = -1 // there is no opening bracket at index 2, so return -1
solve("((1)23(45))(aB)", 6) = 9
solve("((1)23(45))(aB)", 11) = 14
solve("((>)|?(*'))(yZ)", 11) = 14

Input will consist of letters, numbers, and special characters, but no spaces. The only brackets will be ( and ).

How to Presign an S3 URL in AWS using AWS CLI

Sat, 05 Mar 2022 00:05:00 +0000

You can use the AWS CLI to presign URLs so that objects in S3 can be shared publicly even if they are set as private.

Presigned URLs are great for sharing private files in an S3 bucket

aws s3 presign s3://<bucket>/<file.jpg>

This can also be coupled with an expiry duration:

aws s3 presign s3://<bucket>/<file.jpg> --expires-in 3600

How to Download using Aria2c with Multiple Connections

Fri, 04 Mar 2022 00:06:00 +0000

If you use aria2c to download files using the command-line, then you can also use it to download using multiple connections.

aria2c -x16 -s16 <url>

-x**, –max-connection-per-server=**

The maximum number of connections to one server for each download. Default: 1

-s**, –-split=**

Download a file using N connections. Default: 5

How to Parse HTML/CSS Colors in Java

Thu, 03 Mar 2022 00:05:00 +0000

The challenge

In this challenge, you parse RGB colors represented by strings. The formats are primarily used in HTML and CSS. Your task is to implement a function that takes a color as a string and returns the parsed color as a map (see Examples).

The input string represents one of the following:

6-digit hexadecimal – “#RRGGBB”
e.g. “#012345”, “#789abc”, “#FFA077”
Each pair of digits represents a value of the channel in hexadecimal: 00 to FF
3-digit hexadecimal – “#RGB”
e.g. “#012”, “#aaa”, “#F5A”
Each digit represents a value 0 to F which translates to 2-digit hexadecimal: 0->00, 1->11, 2->22, and so on.
Preset color name
e.g. “red”, “BLUE”, “LimeGreen”
You have to use the predefined map PRESET_COLORS (JavaScript, Python, Ruby), presetColors (Java, C#, Haskell), or preset-colors (Clojure). The keys are the names of preset colors in lower-case and the values are the corresponding colors in 6-digit hexadecimal (same as 1. “#RRGGBB”).

parse("#80FFA0") === new RGB(128, 255, 160))
parse("#3B7") === new RGB( 51, 187, 119))
parse("LimeGreen") === new RGB( 50, 205,  50))

// RGB class is defined as follows:
final class RGB {
    public int r, g, b;
    
    public RGB();
    public RGB(int r, int g, int b);
}

The solution in Java code

Option 1:

Solving Simple Transposition in Java

Wed, 02 Mar 2022 00:05:00 +0000

The challenge

Simple transposition is a basic and simple cryptography technique. We make 2 rows and put first a letter in Row 1, the second in Row 2, third in Row 1, and so on until the end. Then we put the text from Row 2 next to the Row 1 text and that’s it.

Complete the function that receives a string and encrypts it with this simple transposition.

For example, if the text to encrypt is: "Simple text", the 2 rows will be:

How to Binary to Text (ASCII) Conversion in Python

Tue, 01 Mar 2022 00:05:00 +0000

The challenge

Write a function that takes in a binary string and returns the equivalent decoded text (the text is ASCII encoded).

Each 8 bits on the binary string represent 1 character on the ASCII table.

The input string will always be a valid binary string.

Characters can be in the range from “00000000” to “11111111” (inclusive)

Note: In the case of an empty binary string your function should return an empty string.

How to Find the Row of the Odd Triangle in Python

Mon, 28 Feb 2022 00:05:00 +0000

The challenge

Given a triangle of consecutive odd numbers:

             1
          3     5
       7     9    11
   13    15    17    19
21    23    25    27    29
...

find the triangle’s row knowing its index (the rows are 1-indexed), e.g.:

odd_row(1)  ==  [1]
odd_row(2)  ==  [3, 5]
odd_row(3)  ==  [7, 9, 11]

Note: your code should be optimized to handle big inputs.

The solution in Python code

Option 1:

def odd_row(n):
    m = (n - 1) * n + 1
    return [*range(m, m + n * 2, 2)]

Option 2:

Solving Number Zoo Patrol in Python

Sun, 27 Feb 2022 00:05:00 +0000

The challenge

Write a function that takes a shuffled list of unique numbers from 1 to n with one element missing (which can be any number including n). Return this missing number.

Note: huge lists will be tested.

Examples:

[1, 3, 4]  =>  2
[1, 2, 3]  =>  4
[4, 2, 3]  =>  1

The solution in Python code

Option 1:

def find_missing_number(a):
    n = len(a) + 1
    return n * (n + 1) // 2 - sum(a)

Option 2:

Common AWS CDK CLI Commands

Sat, 26 Feb 2022 00:05:00 +0000

The AWS Cloud Development Kit (CDK) comes with numerous CLI commands.

Command	Function
cdk list (ls)	Lists the stacks in the application
cdk synthesize (synth)	Synthesizes and prints the AWS CloudFormation template for the specified stack or stacks
cdk bootstrap	Deploys the AWS CDK Toolkit stack, required to deploy stacks containing assets
cdk deploy	Deploys the specified stacks
cdk destroy	Destroys the specified stacks
cdk diff	Compares the specified stack with the deployed stack or a local AWS CloudFormation template
cdk metadata	Displays metadata about the specified stack
cdk init	Creates a new AWS CDK project in the current directory from a specified template
cdk context	Manages cached context values
cdk docs (doc)	Opens the AWS CDK API reference in your browser
cdk doctor	Checks your AWS CDK project for potential problems

Learn more about AWS CDK here, or read the Official Guides here.

How to Create an S3 bucket with PublicRead in CloudFormation

Fri, 25 Feb 2022 00:05:00 +0000

AWSTemplateFormatVersion: 2010-09-09
Description: Basic S3 Bucket CloudFormation template

Resources:
  S3BucketForWebsiteContent:
    Type: AWS::S3::Bucket
    Properties:
      AccessControl: PublicRead

Outputs:
  BucketName:
    Value: !Ref S3BucketForWebsiteContent
    Description: Name of the newly created Amazon S3 Distribution

How to Create a VPC in CloudFormation

Thu, 24 Feb 2022 00:05:00 +0000

It’s very easy to deploy a VPC using CloudFormation:

AWSTemplateFormatVersion: 2010-09-09
Description: Deploy a VPC

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsHostnames: true
      Tags:
      - Key: Name
        Value: Lab VPC
<meta charset="utf-8">Outputs:
  VPC:
    Description: VPC
    Value: !Ref VPC

This will also output the created VPC resource information.

But what if you also want to create Subnets and an attached Internet Gateway?

AWSTemplateFormatVersion: 2010-09-09
Description: Deploy a VPC

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsHostnames: true
      Tags:
      - Key: Name
        Value: Lab VPC

  InternetGateway:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
      - Key: Name
        Value: Lab Internet Gateway

  AttachGateway:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway

  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.0.0/24
      AvailabilityZone: !Select 
        - '0'
        - !GetAZs ''
      Tags:
        - Key: Name
          Value: Public Subnet 1

  PrivateSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: !Select 
        - '0'
        - !GetAZs ''
      Tags:
        - Key: Name
          Value: Private Subnet 1

  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: Public Route Table

  PublicRoute:
    Type: AWS::EC2::Route
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway

  PublicSubnetRouteTableAssociation1:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnet1
      RouteTableId: !Ref PublicRouteTable

  PrivateRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
      - Key: Name
        Value: Private Route Table

  PrivateSubnetRouteTableAssociation1:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PrivateSubnet1
      RouteTableId: !Ref PrivateRouteTable

Outputs:
  VPC:
    Description: VPC
    Value: !Ref VPC
  AZ1:
    Description: Availability Zone 1
    Value: !GetAtt 
      - PublicSubnet1
      - AvailabilityZone

How to Setup Git on EC2 for AWS CodeCommit

Wed, 23 Feb 2022 00:05:00 +0000

Connect to the instance:

chmod 400 KEYPAIR.pem
ssh -i KEYPAIR.pem ec2-user@EC2PublicIP

Install Git:

sudo yum install -y git

Setup Git Credential Helper:

git config --global credential.helper '!aws codecommit credential-helper $@'
git config --global credential.UseHttpPath true

Now you can clone the CodeCommit repo which will look something like the following:

https:&#47;&#47;git-codecommit.us-east-1.amazonaws.com/v1/repos/My-Repo

The Difference of 2 in Java

Tue, 22 Feb 2022 00:05:00 +0000

The challenge

The objective is to return all pairs of integers from a given array of integers that have a difference of 2.

The resulting array should be sorted in ascending order of values.

Assume there are no duplicate integers in the array. The order of the integers in the input array should not matter.

[1, 2, 3, 4]  should return [[1, 3], [2, 4]]
[4, 1, 2, 3]  should also return [[1, 3], [2, 4]]
[1, 23, 3, 4, 7] should return [[1, 3]]
[4, 3, 1, 5, 6] should return [[1, 3], [3, 5], [4, 6]]

The solution in Java code

Option 1:

How to Make the Deadfish Swim in Java

Mon, 21 Feb 2022 00:05:00 +0000

The challenge

Write a simple parser that will parse and run Deadfish.

Deadfish has 4 commands, each 1 character long:

i increments the value (initially ``)
d decrements the value
s squares the value
o outputs the value into the return array

Invalid characters should be ignored.

Deadfish.parse("iiisdoso") =- new int[] {8, 64};

The solution in Java code

Option 1:

import java.util.ArrayList;
import java.util.List;

public class DeadFish {
  public static int[] parse(String data) {
    int value = 0;
    List<Integer> result = new ArrayList<>();
    for(char letter : data.toCharArray()) {
      switch(letter) {
        case 'i': value++; break;
        case 'd': value--; break;
        case 's': value *= value; break;
        case 'o': result.add(value); break;
        default: throw new IllegalArgumentException("Not valid code letter");
      }
    }
    return result.stream().mapToInt(Integer::intValue).toArray();
  }
}

Option 2:

How to Write Number in Expanded Form in Java

Sun, 20 Feb 2022 00:05:00 +0000

The challenge

You will be given a number and you will need to return it as a string in Expanded Form.

Examples:

Challenge.expandedForm(12); // Should return "10 + 2"
Challenge.expandedForm(42); // Should return "40 + 2"
Challenge.expandedForm(70304); // Should return "70000 + 300 + 4"

NOTE: All numbers will be whole numbers greater than 0.

The solution in Java code

Option 1:

public class Challenge {
    public static String expandedForm(int num) {
      StringBuffer res = new StringBuffer();
      int d = 1;
      while(num > 0) {
        int nextDigit = num % 10;        
        num /= 10;
        if (nextDigit > 0) {
          res.insert(0, d * nextDigit);
          res.insert(0, " + ");
        }
        d *= 10;
      }
      return res.substring(3).toString();
    }
}

Option 2:

Is a Number Prime in Java

Sat, 19 Feb 2022 00:05:00 +0000

The challenge

Define a function that takes one integer argument and returns a logical value true or false depending on if the integer is a prime.

Per Wikipedia, a prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

You can assume you will be given an integer input.
You can not assume that the integer will be only positive. You may be given negative numbers as well (or ``).
NOTE on performance: There are no fancy optimizations required, but still the most trivial solutions might time out. Numbers go up to 2^31 (or similar, depends on language version). Looping all the way up to n, or n/2, will be too slow.

is_prime(1)  /* false */
is_prime(2)  /* true  */
is_prime(-1) /* false */

The solution in Java code

Option 1:

How to Calculate Minutes to Midnight in Java

Fri, 18 Feb 2022 00:05:00 +0000

The challenge

Write a function minutesToMidnight(d) that will take a date object as the parameter. Return the number of minutes in the following format:

“x minute(s)”

You will always get a date object with of today with a random timestamp.
You have to round the number of minutes.
Milliseconds don’t matter!Some examples: 10.00 am => "840 minutes" 23.59 pm => "1 minute"

The solution in Java code

Option 1:

import java.util.Date;

public class Minute {
  public String countMinutes(Date d){
     int mins=(24-d.getHours()-1)*60+60-d.getMinutes();
     if (d.getHours()==23 && d.getMinutes()==59) return "1 minute";
     return (d.getSeconds()!=0)?  ""+(mins-1)+" minutes" : ""+mins+" minutes";
  }
}

Option 2:

How to Change the Timestamp of a File on Mac/Linux

Thu, 17 Feb 2022 00:05:00 +0000

If you have a file on your machine, and you want to change the created/modified time/date stamp, then you can use the touch command.

touch -t 202202011308.57 someFile.jpg

In the above example, the timestamp will be changed to <meta charset="utf-8">2022-02-01 13:08:57.

Simply remove all non-decimal characters and place a period before the seconds.

How to Round up to the Next Multiple of 5 in Python

Wed, 16 Feb 2022 00:05:00 +0000

The challenge

Given an integer as input, can you round it to the next (meaning, “higher”) multiple of 5?

Examples:

input:    output:
0    ->   0
2    ->   5
3    ->   5
12   ->   15
21   ->   25
30   ->   30
-2   ->   0
-5   ->   -5
etc.

Input may be any positive or negative integer (including 0).

You can assume that all inputs are valid integers.

The solution in Python code

Option 1:

How to get the Sum of the First nth Term of a Series in Java

Tue, 15 Feb 2022 00:05:00 +0000

The challenge

Your task is to write a function that returns the sum of the following series up to nth term(parameter).

Series: 1 + 1/4 + 1/7 + 1/10 + 1/13 + 1/16 +...

You need to round the answer to 2 decimal places and return it as String.
If the given value is 0 then it should return 0.00
You will only be given Natural Numbers as arguments.

1 --> 1 --> "1.00"
2 --> 1 + 1/4 --> "1.25"
5 --> 1 + 1/4 + 1/7 + 1/10 + 1/13 --> "1.57"

The solution in Java code

Option 1:

How to satisfy Wilson Primes in Python

Mon, 14 Feb 2022 00:05:00 +0000

The challenge

Wilson primes satisfy the following condition. Let P represent a prime number.

Then ((P-1)! + 1) / (P * P) should give a whole number.

Your task is to create a function that returns true if the given number is a Wilson prime.

The solution in Python code

Option 1:

def am_i_wilson(n):
    return n in (5, 13, 563)

Option 2:

def am_i_wilson(n):
    if n < 2 or not all(n % i for i in xrange(2, n)):
        return False
    
    import math
    return (math.factorial(n - 1) + 1) % (n ** 2) == 0

Option 3:

How to Boot an EC2 with a WebServer Setup

Sun, 13 Feb 2022 00:05:00 +0000

Create a new AWS EC2 instance, and set the User Script to the following:

#!/bin/bash
sudo su
yum update -y
yum install -y httpd.x86_64
systemctl start httpd.service
systemctl enable httpd.service
echo "<h1>Serving from $(hostname -f)</h1>" > /var/www/html/index.html

Writing a Sleigh Authentication in Python

Sat, 12 Feb 2022 00:05:00 +0000

The challenge

Christmas is coming and many people dreamed of having a ride with Santa’s sleigh. But, of course, only Santa himself is allowed to use this wonderful transportation. And in order to make sure, that only he can board the sleigh, there’s an authentication mechanism.

Your task is to implement the authenticate() method of the sleigh, which takes the name of the person, who wants to board the sleigh and a secret password. If, and only if, the name equals “Santa Claus” and the password is “Ho Ho Ho!” (yes, even Santa has a secret password with uppercase and lowercase letters and special characters :D), the return value must be true. Otherwise, it should return false.

Solving for Multiple of Index in Python

Fri, 11 Feb 2022 00:05:00 +0000

The challenge

Return a new array consisting of elements which are multiple of their own index in input array (length > 1).

Examples:

[22, -6, 32, 82, 9, 25] => [-6, 32, 25]

[68, -1, 1, -7, 10, 10] => [-1, 10]

[-56,-85,72,-26,-14,76,-27,72,35,-21,-67,87,0,21,59,27,-92,68] => [-85, 72, 0, 68]

The solution in Python code

Option 1:

def multiple_of_index(l):
    return [l[i] for i in range(1, len(l)) if l[i] % i == 0]

Option 2:

How to Find an item’s Alphabet Position in Python

Thu, 10 Feb 2022 00:05:00 +0000

The challenge

When provided with a letter, return its position in the alphabet.

Input :: “a”

Ouput :: “Position of alphabet: 1”

The solution in Python code

Option 1:

def position(alphabet):
    return "Position of alphabet: {}".format(ord(alphabet) - 96)

Option 2:

from string import ascii_lowercase
def position(char):
    return "Position of alphabet: {0}".format(
        ascii_lowercase.index(char) + 1)

Option 3:

def position(alphabet):
    return "Position of alphabet: %s" % ("abcdefghijklmnopqrstuvwxyz".find(alphabet) + 1)

Test cases to validate our solution

import test
from solution import position

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():

        tests = [
            # [input, expected]
            ["a", "Position of alphabet: 1"],
            ["z", "Position of alphabet: 26"],
            ["e", "Position of alphabet: 5"],
        ]
        
        for inp, exp in tests:
            test.assert_equals(position(inp), exp)

How to Keep up the Hoop in Java

Wed, 09 Feb 2022 00:05:00 +0000

The challenge

Alex just got a new hula hoop, he loves it but feels discouraged because his little brother is better than him

Write a program where Alex can input (n) how many times the hoop goes round and it will return him an encouraging message 🙂

If Alex gets 10 or more hoops, return the string “Great, now move on to tricks”.
If he doesn’t get 10 hoops, return the string “Keep at it until you get it”.

The solution in Java code

Option 1:

Will there be Enough Space in Java

Tue, 08 Feb 2022 00:05:00 +0000

The challenge

Bob is working as a bus driver. However, he has become extremely popular amongst the city’s residents. With so many passengers wanting to get aboard his bus, he sometimes has to face the problem of not having enough space left on the bus! He wants you to write a simple program telling him if he will be able to fit all the passengers.

You have to write a function that accepts three parameters:

How to Swap Node Pairs In Linked List in Java

Mon, 07 Feb 2022 00:05:00 +0000

The challenge

If you are given the head node in a linked list, write a method that swaps each pair of nodes in the list, then returns the head node of the list.

Example:

if you are given a list ordered A,B,C,D the resulting list should be B,A,D,C.

The list will be composed of Nodes of the following specification:

public class Node {
    private String value;
    public Node next;

    public Node(String value) { this.value = value; }

    public String getValue() { return value; }
    
    public String toString() { return this.value; }
    
    public String printList() {
      if (this.next == null) return this.toString() + " ->";
      return this.toString() + " -> " + next.printList();
    }
}

The solution in Java code

Option 1:

How to Solve ‘Finding Neo’ in Java

Sun, 06 Feb 2022 00:05:00 +0000

The challenge

Neo is somewhere in the Matrix.

public interface Matrix {
  public int size();
  public int get(int x, int y);
}

You are Morpheus, and your job is to find him.

public class Morpheus {
  public int[] find(Matrix matrix, int neo) {
    // return Neo's x and y coordinates as a two-element array
  }
}

You will need a good search strategy – the matrix is huge! But it is controlled by machines, so it is also very orderly. It is quadratic, and the following rules hold for all elements:

How to Solve a Pandigital Sequence in Java

Sat, 05 Feb 2022 00:05:00 +0000

The challenge

In mathematics, a pandigital number is a number that in a given base has among its significant digits each digit used in the base at least once. For example, 1234567890 is a pandigital number in base 10.

For simplification, in this challenge, we will consider pandigital numbers in base 10 and with all digits used exactly once. The challenge is to calculate a sorted sequence of pandigital numbers, starting at a certain offset and with a specified size.

How to get Meta-Data information from an AWS EC2 Instance

Fri, 04 Feb 2022 00:05:00 +0000

If you need to query meta-data information from your running EC2 instance, you can curl the following location:

curl http://169.254.169.254/latest/meta-data

This will provide a list of all information that can be retrieved.

Say you want to get the local IPv4 address, this can be done as follows:

curl http://169.254.169.254/latest/meta-data/local-ipv4

You can also get JSON blocks of information back, such as querying the IAM Info:

curl http://169.254.169.254/latest/meta-data/iam/info

How to write a Lazy Repeater Helper in Python

Thu, 03 Feb 2022 00:05:00 +0000

The challenge

The make_looper() function takes a string (of non-zero length) as an argument. It returns a function. The function it returns will return successive characters of the string on successive invocations. It will start back at the beginning of the string once it reaches the end.

Examples:

abc = make_looper('abc')
abc() # should return 'a' on this first call
abc() # should return 'b' on this second call
abc() # should return 'c' on this third call
abc() # should return 'a' again on this fourth call

The solution in Python code

Option 1:

How to write a String Case Conversion Helper in Python

Wed, 02 Feb 2022 00:05:00 +0000

The challenge

In this challenge, you will make a function that converts between camelCase, snake_case, and kebab-case.

You must write a function that changes to a given case. It must be able to handle all three case types:

change_case("snakeCase", "snake") # "snake_case"
change_case("some-lisp-name", "camel") # "someLispName"
change_case("map_to_all", "kebab") # "map-to-all"
change_case("doHTMLRequest", "kebab") # "do-h-t-m-l-request"
change_case("invalid-inPut_bad", "kebab") # None
change_case("valid-input", "huh???") # None
change_case("", "camel") # ""

Your function must deal with invalid input as shown, though it will only be passed strings. Furthermore, all valid identifiers will be lowercase except when necessary, in other words on word boundaries in camelCase.

How to create Interleaving Arrays in Python

Tue, 01 Feb 2022 00:05:00 +0000

The challenge

Create a function, that accepts an arbitrary number of arrays and returns a single array generated by alternately appending elements from the passed-in arguments. If one of them is shorter than the others, the result should be padded with empty elements.

Examples:

interleave([1, 2, 3], ["c", "d", "e"]) == [1, "c", 2, "d", 3, "e"]
interleave([1, 2, 3], [4, 5]) == [1, 4, 2, 5, 3, None]
interleave([1, 2, 3], [4, 5, 6], [7, 8, 9]) == [1, 4, 7, 2, 5, 8, 3, 6, 9]
interleave([]) == []

The solution in Python code

Option 1:

How to Find the Largest product in a Series in Python

Mon, 31 Jan 2022 00:05:00 +0000

The challenge

Complete the greatestProduct method so that it’ll find the greatest product of five consecutive digits in the given string of digits.

Example:

greatestProduct("123834539327238239583") # should return 3240

The input string always has more than five digits.

The solution in Python code

Option 1:

from itertools import islice
from functools import reduce

def greatest_product(n):
    numbers=[int(value) for value in n]
    result=[reduce(lambda x,y: x*y, islice(numbers, i, i+5), 1) for i in range(len(numbers)-4)]
    return max(result)

Option 2:

How to Calculate the Least Common Multiple in Python

Sun, 30 Jan 2022 00:05:00 +0000

The challenge

Write a function that calculates the least common multiple of its arguments; each argument is assumed to be a non-negative integer. In the case that there are no arguments (or the provided array in compiled languages is empty), return 1.

The solution in Python code

Option 1:

from math import gcd
def lcm(*args):
    lcm=1
    for x in args:
        if x!=0:
            lcm=lcm*x//gcd(lcm,x)
        else:
            lcm=0
    return lcm

Option 2:

def lcm(*args):
    gcd = lambda m,n: m if not n else gcd(n,m%n)
    return reduce( lambda x, y: x*y/gcd(x, y), args)

Option 3:

How to Solve Caesar Cipher Helper in Python

Sat, 29 Jan 2022 00:05:00 +0000

The challenge

Write a class that, when given a string, will return an uppercase string with each letter shifted forward in the alphabet by however many spots the cipher was initialized to.

Example:

c = CaesarCipher(5); # creates a CipherHelper with a shift of five
c.decode('BFKKQJX') # returns 'WAFFLES'

If something in the string is not in the alphabet (e.g. punctuation, spaces), simply leave it as is.
The shift will always be in the range of [1, 26].

How to Write Out Numbers in Python

Fri, 28 Jan 2022 00:05:00 +0000

The challenge

Create a function that transforms any positive number to a string representing the number in words. The function should work for all numbers between 0 and 999999.

number2words(0)  ==>  "zero"
number2words(1)  ==>  "one"
number2words(9)  ==>  "nine"
number2words(10)  ==>  "ten"
number2words(17)  ==>  "seventeen"
number2words(20)  ==>  "twenty"
number2words(21)  ==>  "twenty-one"
number2words(45)  ==>  "forty-five"
number2words(80)  ==>  "eighty"
number2words(99)  ==>  "ninety-nine"
number2words(100)  ==>  "one hundred"
number2words(301)  ==>  "three hundred one"
number2words(799)  ==>  "seven hundred ninety-nine"
number2words(800)  ==>  "eight hundred"
number2words(950)  ==>  "nine hundred fifty"
number2words(1000)  ==>  "one thousand"
number2words(1002)  ==>  "one thousand two"
number2words(3051)  ==>  "three thousand fifty-one"
number2words(7200)  ==>  "seven thousand two hundred"
number2words(7219)  ==>  "seven thousand two hundred nineteen"
number2words(8330)  ==>  "eight thousand three hundred thirty"
number2words(99999)  ==>  "ninety-nine thousand nine hundred ninety-nine"
number2words(888888)  ==>  "eight hundred eighty-eight thousand eight hundred eighty-eight"

The solution in Python code

Option 1:

How to do Base64 Encoding in Python

Thu, 27 Jan 2022 00:05:00 +0000

The challenge

Create a function that converts the value of the String to and from Base64 using the ASCII character set.

Do not use built-in functions.

Examples:

# should return 'dGhpcyBpcyBhIHN0cmluZyEh'
to_base_64('this is a string!!')

# should return 'this is a string!!'
from_base_64('dGhpcyBpcyBhIHN0cmluZyEh')

You can learn more about Base64 encoding and decoding here.

The solution in Python code

Option 1:

CODES = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
def to_base_64(string):
    padding = 3 - len(string) % 3 if len(string) % 3 else 0
    binary = ''.join(format(ord(i),'08b') for i in string) + '00'*padding
    return ''.join(CODES[int(binary[i:i+6], 2)] for i in range(0, len(binary), 6))
    
def from_base_64(string):
    binary = ''.join(format(CODES.find(i),'06b') for i in string)
    return ''.join(chr(int(binary[i:i+8], 2)) for i in range(0, len(binary), 8)).rstrip('\x00')

Option 2:

How to Calculate Transport on Vacation in Java

Wed, 26 Jan 2022 00:05:00 +0000

The challenge

After a hard quarter in the office you decide to get some rest on a vacation. So you will book a flight for you and your girlfriend and try to leave all the mess behind you.

You will need a rental car in order for you to get around in your vacation. The manager of the car rental makes you some good offers.

Every day you rent the car costs $40. If you rent the car for 7 or more days, you get $50 off your total. Alternatively, if you rent the car for 3 or more days, you get $20 off your total.

Playing with the letter ‘E’ in Java

Tue, 25 Jan 2022 00:05:00 +0000

The challenge

Given String str, return:

If given String doesn’t contain any “e”, return: “There is no “e”.”
If given String is empty, return empty String.
If given String is `null`

The solution in Java code

Option 1:

public class WithoutLetterE {
  public static String findE(String str){
    if (str==null) return null;
    if (str.equals("")) return "";
    int len = str.length() - str.toLowerCase().replaceAll("e", "").length();
    if (len > 0) return String.valueOf(len);
    if (!str.contains("e")) return "There is no \"e\".";
    return null;
  }
}

Option 2:

How to Sum the Average for NBA Players in Golang

Mon, 24 Jan 2022 00:05:00 +0000

The challenge

Write a function, called sumPPG, that takes two NBA player objects/struct/Hash/Dict/Class and sums their PPG

iverson := NBAPlayer{ Team: "76ers", Ppg: 11.2 }
jordan  := NBAPlayer{ Team: "bulls", Ppg: 20.2 }
SumPpg(iverson, jordan) // => 31.4

The solution in Golang

Option 1:

package solution
type NBAPlayer struct {
  Team string
  Ppg  float64
}
func SumPpg(playerOne, playerTwo NBAPlayer) float64 {
  return playerOne.Ppg+playerTwo.Ppg  
}

Option 2:

package solution
type NBAPlayer struct {
  Team string
  Ppg  float64
}
func SumPpg(a, b NBAPlayer) float64 {
  return float64(a.Ppg + b.Ppg)
}

Test cases to validate our solution

package solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
)
const tol=1e-6
var _ = Describe("Fixed tests", func() {
   It("Iverson and jordan", func() {
     iverson := NBAPlayer{ Team: "76ers", Ppg: 11.2 }
     jordan  := NBAPlayer{ Team: "bulls", Ppg: 20.2 }
     Expect(SumPpg(iverson,jordan)).To(BeNumerically("~",31.4,tol))
   })
  It("Standard tests", func(){
    player1 := NBAPlayer{ Team: "p1_team", Ppg: 20.2   }
    player2 := NBAPlayer{ Team: "p2_team", Ppg: 2.6    }
    player3 := NBAPlayer{ Team: "p3_team", Ppg: 2023.2 }
    player4 := NBAPlayer{ Team: "p4_team", Ppg: 0      }
    player5 := NBAPlayer{ Team: "p5_team", Ppg: -5.8   }
    Expect(SumPpg(player1, player2)).To(BeNumerically("~",22.8      ,tol))
    Expect(SumPpg(player3, player1)).To(BeNumerically("~",2043.4    ,tol))
    Expect(SumPpg(player3, player4)).To(BeNumerically("~",2023.2    ,tol))
    Expect(SumPpg(player4, player5)).To(BeNumerically("~",-5.8      ,tol))
    Expect(SumPpg(player5, player2)).To(BeNumerically("~",2.6 - 5.8 ,tol))
  })
})

How to Compute a Cube as Sums in Golang

Sun, 23 Jan 2022 00:05:00 +0000

The challenge

You will be given a number n (where n >= 1) and your task is to find n consecutive odd numbers whose sum is exactly the cube of n.

**Mathematically:
** cube = n ** 3
sum = a1 + a2 + a3 + ….. + an
sum == cube
a2 == a1 + 2, a3 == a2 + 2, …….

For example:

FindSummands(3) == []int{7,9,11}
// ..because 7 + 9 + 11 = 27, the cube of 3.
// Note that there are only n = 3 elements in the array.

Write function findSummands(n) which will return an array of n consecutive odd numbers with the sum equal to the cube of n (n*n*n).

The Deaf Rats of Hamelin Challenge in Java

Sat, 22 Jan 2022 00:05:00 +0000

The challenge

The Pied Piper has been enlisted to play his magical tune and coax all the rats out of town.

But some of the rats are deaf and are going the wrong way!

How many deaf rats are there?

P = The Pied Piper
O~ = Rat going left
~O = Rat going right

ex1 ~O~O~O~O P has 0 deaf rats
ex2 P O~ O~ ~O O~ has 1 deaf rat
ex3 ~O~O~O~OP~O~OO~ has 2 deaf rats

The solution in Java code

Option 1:

How to Find the Next Perfect Square in Java

Fri, 21 Jan 2022 00:05:00 +0000

The challenge

You might know some pretty large perfect squares. But what about the NEXT one?

Complete the findNextSquare method that finds the next integral perfect square after the one passed as a parameter. Recall that an integral perfect square is an integer n such that sqrt(n) is also an integer.

If the parameter is itself not a perfect square then -1 should be returned. You may assume the parameter is non-negative.

How to Find the Unique String in Python

Thu, 20 Jan 2022 00:05:00 +0000

The challenge

There is an array of strings. All strings contain similar letters except one. Try to find it!

find_uniq([ 'Aa', 'aaa', 'aaaaa', 'BbBb', 'Aaaa', 'AaAaAa', 'a' ]) # => 'BbBb'
find_uniq([ 'abc', 'acb', 'bac', 'foo', 'bca', 'cab', 'cba' ]) # => 'foo'

Strings may contain spaces. Spaces are not significant, only non-spaces symbols matter.
E.g. A string that contains only spaces is like an empty string.

It’s guaranteed that the array contains more than 3 strings.

How to convert a PascalCase string into snake_case in Python

Wed, 19 Jan 2022 00:05:00 +0000

The challenge

Complete the function/method so that it takes a PascalCase string and returns the string in snake_case notation. Lowercase characters can be numbers. If the method gets a number as input, it should return a string.

"TestController"  -->  "test_controller"
"MoviesAndBooks"  -->  "movies_and_books"
"App7Test"        -->  "app7_test"
1                 -->  "1"

The solution in Python code

Option 1:

import re

def to_underscore(string):
    return re.sub(r'(.)([A-Z])', r'\1_\2', str(string)).lower()

Option 2:

def to_underscore(string):
    string = str(string)
    camel_case = string[0].lower()
    for c in string[1:]:
        camel_case += '_{}'.format(c.lower()) if c.isupper() else c
    return camel_case

Option 3:

How to Convert a Hex String to RGB in Python

Tue, 18 Jan 2022 00:05:00 +0000

The challenge

When working with color values it can sometimes be useful to extract the individual red, green, and blue (RGB) component values for a color. Implement a function that meets these requirements:

Accepts a case-insensitive hexadecimal color string as its parameter (ex. "#FF9933" or "#ff9933")
Returns a Map<String, int> with the structure {r: 255, g: 153, b: 51} where r, g, and b range from 0 through 255

Note: your implementation does not need to support the shorthand form of hexadecimal notation (ie "#FFF")

How to Create a Hashtag Generator in Python

Mon, 17 Jan 2022 00:05:00 +0000

The challenge

Write a hashtag generator function that takes a string and returns a #HashCodeString of it.

The hashtag generator should perform the following tasks.

Follow these rules:

It must start with a hashtag (#).
All words must have their first letter capitalized.
If the final result is longer than 140 chars it must return false.
If the input or the result is an empty string it must return false.

"    Hello     World   "                  =>  "#HelloWorld"
""                                        =>  false

The solution in Python code

Option 1:

How to Move Zeros to the End in Python

Sun, 16 Jan 2022 00:05:00 +0000

The challenge

Write an algorithm that takes an array and moves all of the zeros to the end, preserving the order of the other elements.

move_zeros([1, 0, 1, 2, 0, 1, 3]) # returns [1, 1, 2, 1, 3, 0, 0]

The solution in Python code

Option 1:

def move_zeros(arr):
    l = [i for i in arr if isinstance(i, bool) or i!=0]
    return l+[0]*(len(arr)-len(l))

Option 2:

def move_zeros(array):
    return sorted(array, key=lambda x: x==0 and type(x) is not bool)

Option 3:

Regex for Gregorian Date Validation in Python

Sat, 15 Jan 2022 00:05:00 +0000

The challenge

Write a regular expression that validates the gregorian date in the format “DD.MM.YYYY”

Correct date examples:

"23.12.2008"
"01.08.1994"

Incorrect examples:

"12.23.2008"
"01-Aug-1994"
" 01.08.1994"

Notes:

maximum length of validator is 400 characters to avoid hardcoding. (shortest solution to date is 170 characters)
validator should process leap days (February, 29) correctly.
the date is Gregorian, it’s important to determine if year is leap: https://en.wikipedia.org/wiki/Gregorian_calendar

The solution in Python code

Option 1:

How to Create Your Own Python Split Function

Fri, 14 Jan 2022 00:05:00 +0000

The challenge

Write your own implementation of the built-in split function in Python.

The following rules must be adhered to:

the function cannot use, in any way, the original split or rsplit functions,
the new function must be a generator,
it should behave as the built-in split, so it will be tested that way — think of split() and split('')

The solution in Python

Option 1:

import re
def my_very_own_split(string, delimiter = None):
    if delimiter == '': raise ValueError('empty delimiter')
    if delimiter == None: delimiter = '\s+'
    else: delimiter = re.escape(delimiter)
    pos = 0
    for m in re.finditer(delimiter, string):
        yield string[pos:m.start()]
        pos = m.end()
    yield string[pos:]

Option 2:

How to create a Domain Name Validator in Python

Thu, 13 Jan 2022 00:05:00 +0000

The challenge

Create a domain name validator mostly compliant with RFC 1035, RFC 1123, and RFC 2181

The following rules apply:

Domain name may contain subdomains (levels), hierarchically separated by . (period) character
Domain name must not contain more than 127 levels, including top level (TLD)
Domain name must not be longer than 253 characters (RFC specifies 255, but 2 characters are reserved for trailing dot and null character for root level)
Level names must be composed out of lowercase and uppercase ASCII letters, digits and – (minus sign) character
Level names must not start or end with – (minus sign) character
Level names must not be longer than 63 characters
Top level (TLD) must not be fully numerical

Additionally:

How to start Java Jar as Service on Linux

Wed, 12 Jan 2022 00:05:00 +0000

If you have a Java Jar file, you can run it as a service under Linux/Ubuntu.

sudo ln -s /var/www/japi-0.0.1-SNAPSHOT.jar /etc/init.d/japi

Now you can use the default init.d verbs [start,stop,restart,status].

Additionally, init.d also gives the following.

Usage for your new `init.d` service

Usage: /etc/init.d/japi {start|stop|force-stop|restart|force-reload|status|run}

Start Java Service

sudo /etc/init.d/japi start

Stop Java Service

sudo /etc/init.d/japi stop

Restart Java Service

sudo /etc/init.d/japi restart

Status Information

sudo /etc/init.d/japi status

How to write a validDate Regex in Python

Tue, 11 Jan 2022 00:05:00 +0000

The challenge

Your task is to write a regular expression (regex) that will match a string only if it contains at least one valid date, in the format [mm-dd] (that is, a two-digit month, followed by a dash, followed by a two-digit date, surrounded by square brackets).

You should assume the year in question is not a leap year. Therefore, the number of days each month should have are as follows:

How to Validate Passwords with Regex in Python

Mon, 10 Jan 2022 00:05:00 +0000

The challenge

You need to write regex that will validate a password to make sure it meets the following criteria:

At least six characters long
contains a lowercase letter
contains an uppercase letter
contains a number

Valid passwords will only be alphanumeric characters.

The solution in Python code

Option 1:

from re import compile, VERBOSE

regex = compile("""
^              # begin word
(?=.*?[a-z])   # at least one lowercase letter
(?=.*?[A-Z])   # at least one uppercase letter
(?=.*?[0-9])   # at least one number
[A-Za-z\d]     # only alphanumeric
{6,}           # at least 6 characters long
$              # end word
""", VERBOSE)

Option 2:

How to create a Coordinates Validator in Golang

Sun, 09 Jan 2022 00:05:00 +0000

The challenge

You need to create a function that will validate if given parameters are valid geographical coordinates.

Valid coordinates look like the following: “23.32353342, -32.543534534”. The return value should be either true or false.

Latitude (which is the first float) can be between 0 and 90, positive or negative. Longitude (which is the second float) can be between 0 and 180, positive or negative.

Coordinates can only contain digits, or one of the following symbols (including space after the comma)

How to Validate ISBN-10 numbers in Golang

Sat, 08 Jan 2022 00:05:00 +0000

The challenge

ISBN-10 identifiers are ten digits long. The first nine characters are digits 0-9. The last digit can be 0-9 or X, to indicate a value of 10.

An ISBN-10 number is valid if the sum of the digits multiplied by their position modulo 11 equals zero.

For example:

ISBN     : 1 1 1 2 2 2 3 3 3  9
position : 1 2 3 4 5 6 7 8 9 10

This is a valid ISBN, because:

How to Create a Java GUI App that shows the Logged-in User and Hostname

Fri, 07 Jan 2022 00:05:00 +0000

Create a new file called Application.java and paste the following:

import javax.swing.*;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class Application {
    public static void main(String...args) throws UnknownHostException {
        JFrame frame = new JFrame("Sample App");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300,300);

        String user = System.getProperty("user.name");
        String host = InetAddress.getLocalHost().getHostName();

        JTextArea txt = new JTextArea();
        txt.setText(
                "\n" +
                "  User: "+user+"\n" +
                "  Host: "+host+"\n"
        );
        frame.getContentPane().add(txt);

        frame.setVisible(true);
    }
}

Now open the terminal/command-line and type:

java Application.java

This will show a GUI application that will have a textarea with two lines of text:

How to view a Terraform Module’s Output

Thu, 06 Jan 2022 00:05:00 +0000

An output in Terraform is a way to view the result of an action that has been performed, or resource that has been created.

Let’s say that you have some code to create a Load Balancer, or Assign a Public IP. Once this action is complete, the output block will have access to this created value.

An simple `output` example

outputs.tf

output "instance_ips" {
  value = aws_instance.web.*.public_ip
}

output "lb_address" {
  value = aws_alb.web.public_dns
}

This will output the values to the console once the terraform apply step has successfully run.

How to Count the Characters in Python

Wed, 05 Jan 2022 00:05:00 +0000

The challenge

The goal of this challenge is to write a function that takes two inputs: a string and a character. The function will count the number of times that character appears in the string. The count is case insensitive.

Examples:

count_char("fizzbuzz","z") # 4
count_char("Fancy fifth fly aloof","f") # 5

The character can be any alphanumeric character.

The solution in Python code

Option 1:

def count_char(haystack, needle):
    count = 0
    for c in haystack:
        if c.lower()==needle.lower():
            count+=1
    return count

Option 2:

How to Install Cuda driver for Nvidia on Ubuntu

Tue, 04 Jan 2022 00:05:00 +0000

If you have just upgraded Ubuntu on your AWS g4dn instance and need to install/reinstall Cuda drivers for your Nvidia chipset, then you can run the following:

Install Cuda drivers for Nvidia on Ubuntu

wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-ubuntu1804.pin
sudo mv cuda-ubuntu1804.pin /etc/apt/preferences.d/cuda-repository-pin-600
sudo apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/7fa2af80.pub
sudo add-apt-repository "deb https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/ /"
sudo apt-get update
sudo apt-get -y install cuda

How to get the versions for your own setup

Or follow the wizard here to generate the correct version numbers for your specific environment/platform:

How to List all Running Services on Ubuntu

Mon, 03 Jan 2022 00:05:00 +0000

If you need to view a list of all the services that are either running or stopped (or both) on an Ubuntu server, then you can use the following command:

service --status-all

This will print out a list of services that may look something like this:

# service --status-all
 [ - ]  acpid
 [ + ]  apache-htcacheclean
 [ + ]  apache2
 [ + ]  apparmor
 [ + ]  apport
 [ + ]  atd
 [ - ]  console-setup.sh
 [ + ]  cron
 [ - ]  cryptdisks
 [ - ]  cryptdisks-early
 [ + ]  datadog-agent
 [ + ]  datadog-agent-process
 [ + ]  datadog-agent-trace
 [ + ]  dbus
 [ - ]  docker

Only show Running Services in Ubuntu

If you are only interested in the running services, then we can filter by the [ + ] items:

[Solved] conflict: unable to remove repository reference in Docker

Sun, 02 Jan 2022 00:05:00 +0000

If you get the following error while trying to delete an image in Docker:

Error response from daemon: conflict: unable to remove repository reference "some-image" (must force) - container 3ab4c18d2219 is using its referenced image 133c1827439a

You may already have tried looking for the container, but it seems to not exist!

How to Remove the Docker Container and Image

This usually means that the Docker container has already terminated, and is why you won’t see it running.

How to Upgrade an Ubuntu Server

Sat, 01 Jan 2022 00:05:00 +0000

Upgrading an Ubuntu Server is quite easy, just follow the below commands:

Option 1: Tldr; (just run the below!)

sudo apt-get update && sudo apt-get upgrade
sudo apt dist-upgrade
sudo do-release-upgrade
reboot

Option 2: Follow the steps to Upgrade Ubuntu Server

1: Update the packages:

Start by making sure that you have all the packages and dependencies ready locally before we upgrade

sudo apt-get update && sudo apt-get upgrade

2: Update the dependencies for the distribution:

sudo apt dist-upgrade

How to Solve Two-Sum in Java

Fri, 31 Dec 2021 00:05:00 +0000

The challenge

Write a function that takes an array of numbers (integers for the tests) and a target number. It should find two different items in the array that, when added together, give the target value. The indices of these items should then be returned in a tuple like so: (index1, index2).

For the purposes of this challenge, some tests may have multiple answers; any valid solutions will be accepted.

How to Sort the Gift Code in Java

Thu, 30 Dec 2021 00:05:00 +0000

The challenge

Santa’s senior gift organizer Elf developed a way to represent up to 26 gifts by assigning a unique alphabetical character to each gift. After each gift was assigned a character, the gift organizer Elf then joined the characters to form the gift ordering code.

Santa asked his organizer to order the characters in alphabetical order, but the Elf fell asleep from consuming too much hot chocolate and candy canes! Can you help him out?

How to get the Numericals of a String in Java

Wed, 29 Dec 2021 00:05:00 +0000

You are given an input string.

For each symbol in the string if it’s the first character occurrence, replace it with a ‘1’, else replace it with the amount of times you’ve already seen it.

input   =  "Hello, World!"
result  =  "1112111121311"

input   =  "aaaaaaaaaaaa"
result  =  "123456789101112"

There might be some non-ascii characters in the string.

Note: there will be no int domain overflow (character occurrences will be less than 2 billion).

How to Replace Noun Phrases with Pronouns in Golang

Tue, 28 Dec 2021 00:05:00 +0000

The challenge

A Noun Phrase is a phrase that can be replaced by a pronoun [he/she/it].

For example, in the sentence:

a girl ate the cookie

“A girl” is a Noun Phrase, so we can say “she ate the cookie.” “The cookie” is also a Noun Phrase, so we can even say “she ate it.”

Both of these Noun Phrases are made up of an auxialliary (aux) [the/a] followed by a Noun (N) [girl/cookie].

Maximum Positive Integer Rotations in Golang

Mon, 27 Dec 2021 00:05:00 +0000

The challenge

Write function MaxRot(n) which given a positive integer n returns the maximum number you got doing rotations similar to the above example.

So MaxRot is such as:

MaxRot(56789) should return 68957
MaxRot(38458215) should return 85821534

Examples:

Take a number: 56789. Rotate left, you get 67895.

Keep the first digit in place and rotate left the other digits: 68957.

Keep the first two digits in place and rotate the other ones: 68579.

How to “Dashatize It” in Java

Sun, 26 Dec 2021 00:05:00 +0000

The challenge

Given a variable n,

If n is an integer, Return a string with dash'-'marks before and after each odd integer, but do not begin or end the string with a dash mark. If n is negative, then the negative sign should be removed.

If n is not an integer, return an empty value.

Ex:

dashatize(274) -> '2-7-4'
dashatize(6815) -> '68-1-5'

The solution in Java code

Option 1:

public class Solution {
    public static String dashatize(int num) {
      String n = String.valueOf(Math.abs(num)).replaceAll("-", "");
      return java.util.Arrays.asList(n.split("")).stream()
        .map(ch -> Integer.valueOf(ch) % 2 !=0 ? "-"+ch+"-" : ch)
        .collect(java.util.stream.Collectors.joining(""))
        .replaceAll("--", "-")
        .replaceAll("^-+", "")
        .replaceAll("-+$", "");
    }
}

Option 2:

How to create a Nickname Generator in Python

Sat, 25 Dec 2021 00:05:00 +0000

The challenge

Write a nickname generator function, nicknameGenerator that takes a string name as an argument and returns the first 3 or 4 letters as a nickname.

The nickname generator should perform the following tasks.

If the 3rd letter is a consonant, return the first 3 letters.

nickname("Robert") # "Rob"
nickname("Kimberly") # "Kim"
nickname("Samantha") # "Sam"

If the 3rd letter is a vowel, return the first 4 letters.

nickname("Jeannie") # "Jean"
nickname("Douglas") # "Doug"
nickname("Gregory") # "Greg"

If the string is less than 4 characters, return “Error: Name too short”.

Comparing Array Multiplicities in Java

Fri, 24 Dec 2021 00:05:00 +0000

The challenge

Given two arrays a and b write a function comp(a, b) (orcompSame(a, b)) that checks whether the two arrays have the “same” elements, with the same multiplicities. “Same” means, here, that the elements in b are the elements in a squared, regardless of the order.

a = [121, 144, 19, 161, 19, 144, 19, 11]  
b = [121, 14641, 20736, 361, 25921, 361, 20736, 361]

comp(a, b) returns true because in b 121 is the square of 11, 14641 is the square of 121, 20736 the square of 144, 361 the square of 19, 25921 the square of 161, and so on. It gets obvious if we write b‘s elements in terms of squares:

How to Find the Sum of Angles in Golang

Thu, 23 Dec 2021 00:05:00 +0000

The challenge

Find the total sum of internal angles (in degrees) in an n-sided simple polygon.

N will be greater than 2.

The solution in Golang

Option 1:

package solution
func Angle(n int) int {
    return (n - 2) * 180
}

Option 2:

package solution
func Angle(n int) (r int) {
    r = (n-2)*180
    return
}

Option 3:

package solution
func Angle(n int) int {
    return (n/2-1) * 360 + n%2 * 180
}

Test cases to validate our solution

package solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
)
var _ = Describe("Basic tests", func() {
    It("Angle(3)", func() { Expect(Angle(3)).To(Equal(180)) })
    It("Angle(4)", func() { Expect(Angle(4)).To(Equal(360)) })
})

How to Find the Max Tree Node Value in Java

Wed, 22 Dec 2021 00:05:00 +0000

The challenge

You are given a binary tree. Implement the method findMax which returns the maximal node value in the tree.

For example, the maximum in the following Tree is 11.

              7
            /   \ 
           /     \
          5       2
           \       \
           6        11          
           /\      /
          1  9   4

Note:

Tree node values range is Integer MIN VALUE – Integer MAX VALUE constants.
Tree can unbalanced and unsorted.
Root node is always not null.

You are given a tree node class as follows:

How to String Search with a Wildcard in Java

Tue, 21 Dec 2021 00:05:00 +0000

The challenge

The method below is the most simple string search algorithm. It will find the first occurrence of a word in a text string.

haystack = the whole text

needle = searchword

wildcard = _

find("strike", "i will strike down upon thee"); // return 7

The find method is already made.

The problem is to implement wildcard(s) in the needle. If you have a _ in the needle it will match any character in the haystack.

How to get the AWS AccountID in Terraform

Mon, 20 Dec 2021 00:05:00 +0000

If you are automating AWS resources in Terraform, then you will want to not hardcode things as much as possible.

Terraform makes it possible to pull the account_id from the local credentials.

How to get the AccountID data attributes

Create a data.tf file and place the following item in it:

data "aws_caller_identity" "current" {}

Now the account_id will be available to you within your standard code as follows:

data.aws_caller_identity.current.account_id

How to use the AccountID data attributes

This can now be used in a module, or wherever you need to reference the account id:

Error creating AppStream Fleet – InvalidRoleException

Sun, 19 Dec 2021 00:05:00 +0000

If you get the following error when trying to run some Terraform:

error creating Appstream Fleet (): InvalidRoleException: AppStream 2.0 encountered an error because your service role 'arn:aws:iam::<ACCOUNT_ID>:role/service-role/AmazonAppStreamServiceAccess' is invalid

..then you just need to run your IaC again, as the roles are automatically created when you first interact with the service.

Alternatively, go and have a look at what has already been created in the AWS Console.

What roles are required for AppStream?

Role required by AWS AppStream:

How to Create AWS AppStream resources in Terraform

Sat, 18 Dec 2021 00:05:00 +0000

AWS AppStream has finally made its way into the Terraform AWS Provider.

If you are using hashicorp/aws version 3.67 or above, then you can do the following:

terraform {
  required_version = "~> 1.0"
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.67"
    }
  }
}
provider "aws" {
  region = "eu-west-1"
  default_tags {
    tags = {
      Contact = "you@example.com"
      Environment = "dev"
      DeployedBy = "Automation:Terraform"
    }
  }
}

resource "aws_appstream_fleet" "example" {
  name          = "ao-tmp-fleet-1"
  image_name    = "Amazon-AppStream2-Sample-Image-02-04-2019"
  instance_type = "stream.standard.small"

  compute_capacity {
    desired_instances = 1
  }
}
resource "aws_appstream_stack" "example" {
  name = "ao-tmp-stack-1"
}
resource "aws_appstream_fleet_stack_association" "example" {
  fleet_name = aws_appstream_fleet.example.name
  stack_name = aws_appstream_stack.example.name
}

How to Stop a Goroutine in Golang

Fri, 17 Dec 2021 00:05:00 +0000

It’s possible to stop a Goroutine by sending a value into it via a signal channel:

exit := make(chan bool)
go func() {
    for {
        select {
        case <- exit:
            return
        default:
            // Perform some tasks
        }
    }
}()

// Exit the Goroutine
exit <- true

As an alternative, you could also use a WaitGroup and range over it:

package main
import (
    "fmt"
    "sync"
)
func main() {
    var wg sync.WaitGroup
    c := make(chan bool)
    wg.Add(1)
    go func() {
        defer wg.Done()
        for b := range c {
            fmt.Printf("Hello %t\n", b)
        }
    }()
    c <- true
    c <- true
    close(c)
    wg.Wait()
}

How to Create an Empty Branch in Git

Thu, 16 Dec 2021 00:05:00 +0000

If you need to create an empty branch in git, you can follow one of the below options.

If you are using git version 2.27 or newer, then follow the switch route (option 1) below, otherwise fall back to the older way, using checkout and delete (option 2).

Newer way – Using `switch`:

git switch --orphan <new branch>
git commit --allow-empty -m "Initial commit on orphan branch"
git push -u origin <new branch>

Older way – Using `checkout` and `delete`:

git checkout --orphan <new branch>
git rm -rf .
git commit --allow-empty -m "root commit"
git push origin <new branch>

Get the Consonant Value in Java

Wed, 15 Dec 2021 00:05:00 +0000

The challenge

Given a lowercase string that has alphabetic characters only and no spaces, return the highest value of consonant substrings. Consonants are any letters of the alphabet except "aeiou".

We shall assign the following values: a = 1, b = 2, c = 3, .... z = 26.

For example, for the word “zodiacs”, let’s cross out the vowels. We get: “z o d ia cs”

How to Check for Factor in Python

Tue, 14 Dec 2021 00:05:00 +0000

The challenge

This function should test if the factor is a factor of base.

Return true if it is a factor or false if it is not.

Factors are numbers you can multiply together to get another number.

2 and 3 are factors of 6 because: 2 * 3 = 6

You can find a factor by dividing numbers. If the remainder is 0 then the number is a factor.
You can use the mod operator (%) in most languages to check for a remainder

Examples:

Understanding Bitwise Operators in Python

Mon, 13 Dec 2021 00:05:00 +0000

There are 6 binary/bitwise operators in Python:

Complement/Not (~)
And (&)
Or (|)
XOR (^)
Left Shift (<<)
Right Shift (>>)

A fantastic python method to help us along our journey is bin(). The bin function will return a binary representation of a base 10 integer we pass to it.

>>> bin(1)
'0b1'

>>> bin(5)
'0b101'

Now let’s explore the 6 bitwise operators by learning a bit about each of them.

Word Values Challenge in Java

Sun, 12 Dec 2021 00:05:00 +0000

The challenge

Given a string "abc" and assuming that each letter in the string has a value equal to its position in the alphabet, our string will have a value of 1 + 2 + 3 = 6. This means that: a = 1, b = 2, c = 3 ....z = 26.

You will be given a list of strings and your task will be to return the values of the strings as explained above multiplied by the position of that string in the list. For our purpose, position begins with 1.

How to update/upgrade all Homebrew packages

Sat, 11 Dec 2021 00:05:00 +0000

If you use Homebrew – and you probably should if you’re on a Mac – then you have probably installed various different applications and packages as time went on. It’s probably likely that by now, you have many different packages that are out of date and need to be upgraded to their newer versions.

Luckily, Homebrew makes it very easy to upgrade everything; run the following command to upgrade everything.

[Solved] FirebaseError: Missing or insufficient permissions

Fri, 10 Dec 2021 00:05:00 +0000

Using Firebase and get the following error in the console?

Uncaught Error in onSnapshot: FirebaseError: Missing or insufficient permissions. at new FirestoreError (index.cjs.js:x)

How to fix the Missing or Insufficient Permissions Error

Option 1: Change rules (Recommended)

Login to Firebase
Go to Database -> Rules

Change:

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if false;
    }
  }
}

to:

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if request.auth != null;
    }
  }
}

Option 2: Override Authorization / Disable Security

Login to Firebase
Go to Database -> Rules
Change allow read, write from false to true [for dev]
Change allow read, write from false to request.auth != null [for prod]

[Solved] Error: Cannot find module ‘../lib/cli.js’

Thu, 09 Dec 2021 00:05:00 +0000

If you try and run npm i and get Error: Cannot find module '../lib/cli.js', then you can easily fix the problem by running the following.

How does the error look?

Error: Cannot find module '../lib/cli.js'
Require stack:
- /usr/local/lib/node_modules/npm/bin/npm-cli.js
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:999:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.<anonymous> (/usr/local/lib/node_modules/npm/bin/npm-cli.js:2:1)
    at Module._compile (node:internal/modules/cjs/loader:1095:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1147:10)
    at Module.load (node:internal/modules/cjs/loader:975:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [ '/usr/local/lib/node_modules/npm/bin/npm-cli.js' ]
}

How to solve the Module Not Found error

brew uninstall --ignore-dependencies node
sudo chown -R $(whoami) /usr/local/*
brew cleanup
brew install node

This will uninstall and cleanup your previous node installation, making sure to set the correct permissions, before reinstalling it.

How to use Git Commit in GitHub Actions

Wed, 08 Dec 2021 00:05:00 +0000

If you’ve tried to use git commit in GitHub Actions before, you may have come across the following error messages:

Author identity unknown
*** Please tell me who you are.

Run
  git config --global user.email "you@example.com"
  git config --global user.name "Your Name"

to set your account's default identity.
Omit --global to set the identity only in this repository.

fatal: empty ident name
    (for <runner@fv-az191-422.gxxxxxjfkf.bx.internal.cloudapp.net>) not allowed
Author identity unknown

This can easily be fixed by doing the following:

[Solved] Error acquiring the state lock in Terraform

Tue, 07 Dec 2021 00:05:00 +0000

If you have been handed the Acquiring state lock error message about ConditionalCheckFailedException: The conditional request then you have 2 options for fixing it!

The error looks something like this:

Acquiring state lock. This may take a few moments...
╷
│ Error: Error acquiring the state lock
│ 
│ Error message: ConditionalCheckFailedException: The conditional request
│ failed
│ Lock Info:
│   ID:        3324a6cb-7401-3194-d650-fxxxxxx3864
│   Path:      xxxx-terraformstate-nonprod/env:/xxxx/terraform.tfstate
│   Operation: OperationTypeApply
│   Who:       root@ip-100-65-2-165
│   Version:   1.0.4
│   Created:   2021-11-29 21:00:37.652114035 +0000 UTC
│   Info:
│ 
│ Terraform acquires a state lock to protect the state from being written
│ by multiple users at the same time. Please resolve the issue above and try
│ again. For most commands, you can disable locking with the "-lock=false"
│ flag, but this is not recommended.

There are 3 possible ways to fix this

In short, you want to delete the lock associated. This is achieved by forcing an unlock.

How to Install Chocolatey on Windows PowerShell

Mon, 06 Dec 2021 00:05:00 +0000

chocolatey.org

How to Install Chocolatey in PowerShell

Open PowerShell (Run PowerShell in Administrator mode) and paste the following script:

Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1'))

This will install Chocolatey, and get you to the point of being able to install packages.

How to run PowerShell in Administrator Mode

Sun, 05 Dec 2021 00:05:00 +0000

Some PowerShell commands require elevated permissions to complete.

To do this, you must first open PowerShell in Administrator Mode.

Steps to Run PowerShell as an Administrator

Click Start (super key)
Type powershell
Right-click on Windows PowerShell and select Run as administrator
or;
Select Run as Administrator from the right-hand-side menu.

(Run as Administrator)

The application will now be started in Administrator Mode.

[Solved] Permission denied @ apply2files – /usr/local/lib/node_modules/expo-cli/node_modules/extglob/lib

Sat, 04 Dec 2021 00:05:00 +0000

If you have recently upgraded your MacOS operating system, you may get the following error in your terminal when installing some Homebrew packages:

Error: Permission denied @ apply2files - /usr/local/lib/node_modules/expo-cli/node_modules/.bin/detect-libc

How to solve the Permissions Denied problem

Simply run the following command in your terminal:

sudo chown -R $(whoami):admin /usr/local/* \
&& sudo chmod -R g+rwx /usr/local/*

Or change the user directly:

sudo chown -R ${LOGNAME}:staff /usr/local/lib/node_modules

How to Fix “is not authorized to create managed-rule” in AWS Step Functions

Fri, 03 Dec 2021 00:05:00 +0000

If you have ever received the following error is not authorized to create managed-rule when running a Step Function through Terraform’s AWS Provider, then you may have jumped through many different hoops trying to figure out what was wrong.

What is the Quick Fix?

Open the role in IAM and attach the CloudWatchEventsFullAccess AWS managed policy to the permissions policies.

Need More Information?

IAM Role Principal Policy required to AssumeRole

{
    "Version" : "2012-10-17",
    "Statement" : [
        {
        "Effect" : "Allow",
        "Principal" : {
            "Service" : "states.amazonaws.com"
        },
        "Action" : "sts:AssumeRole"
        }
    ]
}

IAM Role Policy GetEvents For StepFunctions Execution Rule

{
    "Effect": "Allow",
    "Action": [
        "events:PutTargets",
        "events:PutRule",
        "events:DescribeRule"
    ],
    "Resource": [
        "arn:aws:events:[[region]]:[[account]]:rule/StepFunctionsGetEventsForStepFunctionsExecutionRule"
    ]
}

IAM Role Policy under StepFunctions CloudFormation

- Effect: Allow
  Action:
  - events:PutTargets
  - events:PutRule
  - events:DescribeRule
  Resource: 
  - !Sub arn:${AWS::Partition}:events:${AWS::Region}:${AWS::AccountId}:rule/StepFunctionsGetEventsForStepFunctionsExecutionRule

If you need to limit it to a resource, then StepFunctionsGetEventsForStepFunctionsExecutionRule is the one you’re looking for!

How to add Account Condition to AWS Lambda Permissions in Terraform

Thu, 02 Dec 2021 00:05:00 +0000

If you need to lock an AWS Lambda function down to a source account for security reasons (PCI.Lambda.1) then you can do so by using the source_account option of the aws_lambda_permission Terraform resource type.

resource "aws_lambda_permission" "do_something_with_bucket" {
  statement_id   = "AllowExecutionFromS3Bucket"
  action         = "lambda:InvokeFunction"
  function_name  = module.do_something_with_bucket.arn
  principal      = "s3.amazonaws.com"
  source_arn     = var.source_bucket_arn
  source_account = var.account_id # <---------- here
}

We have stored the account_id in a variable so that it can be updated when we initialize our Terraform context:

How to AssumeRole in Terraform LocalExec Provisioner Block

Wed, 01 Dec 2021 00:05:00 +0000

I needed to execute a Terraform null_resource provisioner (local-exec) block to run an awscli command, but assume a role passed down to it.

There was no obvious way to pass the credentials to it, or assume a role directly, so the following workaround did the trick:

AssumeRole and Pass LocalExec Provisioner Command

resource "null_resource" "start-appstream-fleet" {
  provisioner "local-exec" {
    interpreter = ["/bin/bash", "-c"]
    command = <<EOF
set -e
CREDENTIALS=(`aws sts assume-role \
  --role-arn ${local.workspace.role} \
  --role-session-name "start-appstream-fleet" \
  --query "[Credentials.AccessKeyId,Credentials.SecretAccessKey,Credentials.SessionToken]" \
  --output text`)

unset AWS_PROFILE
export AWS_DEFAULT_REGION=us-east-1
export AWS_ACCESS_KEY_ID="$${CREDENTIALS[0]}"
export AWS_SECRET_ACCESS_KEY="$${CREDENTIALS[1]}"
export AWS_SESSION_TOKEN="$${CREDENTIALS[2]}"

aws appstream start-fleet --name sample-app-${var.environment}-fleet --region ${var.region} --output json
EOF
  }
}

The above code snippet runs 2 aws cli commands. The first is to get the credentials, which are then stored in environment variables, followed by consuming them in the actual aws cli command at the bottom.

Split and then add both sides of an array together in Java

Tue, 30 Nov 2021 00:05:00 +0000

The challenge

You will receive an array as a parameter that contains 1 or more integers and a number n.

Here is a little visualization of the process:

Step 1: Split the array in two:[1, 2, 5, 7, 2, 3, 5, 7, 8] / \ [1, 2, 5, 7] [2, 3, 5, 7, 8]
Step 2: Put the arrays on top of each other: [1, 2, 5, 7] [2, 3, 5, 7, 8]
Step 3: Add them together:[2, 4, 7, 12, 15]

Repeat the above steps n times or until there is only one number left, and then return the array.

Highest Rank Number in an Array in Golang

Mon, 29 Nov 2021 00:05:00 +0000

The challenge

Complete the method which returns the number which is most frequent in the given input array. If there is a tie for the most frequent number, return the largest number among them.

Note: no empty arrays will be given.

[12, 10, 8, 12, 7, 6, 4, 10, 12]              -->  12
[12, 10, 8, 12, 7, 6, 4, 10, 12, 10]          -->  12
[12, 10, 8, 8, 3, 3, 3, 3, 2, 4, 10, 12, 10]  -->   3

The solution in Golang

Option 1:

Sort Words by Position Index in Java

Sun, 28 Nov 2021 00:05:00 +0000

The challenge

Your task is to sort a given string. Each word in the string will contain a single number. This number is the position the word should have in the result.

Note: Numbers can be from 1 to 9. So 1 will be the first word (not 0).

If the input string is empty, return an empty string. The words in the input String will only contain valid consecutive numbers.

How to get the Current Machine Name and Logged In User in Java

Sat, 27 Nov 2021 00:05:00 +0000

It’s very easy to get the current machine name and logged in user using Java.

Get the Currently Logged in User

String username = System.getProperty("user.name");

System.out.println("Username logged in: " + username);

This is also platform-independent.

Get the Hostname of the Machine

java.net.InetAddress localMachine = java.net.InetAddress.getLocalHost();
String hostname = localMachine.getHostName();

System.out.println("Hostname of local machine: " + hostname);

How to set ZSH as your default Shell

Fri, 26 Nov 2021 00:05:00 +0000

You may have installed ZSH and every-time you open your terminal, it opens BASH by default.

How do you set your default shell to open as ZSH?

It’s easy, you can just use the change shell command:

chsh -s $(which zsh)

How to Base64 Encode/Decode in the Terminal/CLI

Thu, 25 Nov 2021 00:05:00 +0000

If you need to either Encode or Decode a Base64 value, there are many ways to achieve this, one of them is directly from your commandline itself!

How to Encode a Base64 value in CLI

echo 'This is a test' | base64

This will output a base64 encoded value of VGhpcyBpcyBhIHRlc3QK

How to Decode a Base64 value in CLI

echo VGhpcyBpcyBhIHRlc3QK | base64 --decode

This will output a decoded value from our base64 value of This is a test

How to Enable Syntax Highlighting in Vim

Wed, 24 Nov 2021 00:05:00 +0000

There are a few different ways to enable Syntax Highlighting in Vim.

Option 1 – Edit ~/.vimrc

Add syntax on to your local ~/.vimrc

echo "syntax on" >> ~/.vimrc

Option 2 – Override System Vim (Mac)

cd
vim --version
xcode-select --install
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew doctor
brew install vim --override-system-vim
vim --version

Option 3 – Toggle in Vim

You can use Vim Commands while in Vim itself:

:syntax on

How to Create an AWS Security Group in Terraform - Securing AWS Resources with Terraform Security Groups

Tue, 23 Nov 2021 00:05:00 +0000

Security groups are a critical component for securing resources in AWS. This guide will show you how to create and manage security groups in AWS using Terraform, a popular infrastructure-as-code tool.

Overview of AWS Security Groups

Security groups act as a firewall to control inbound and outbound traffic to AWS resources like EC2 instances, RDS databases, ELB load balancers, etc. They operate at the instance level, not the subnet level.

Some key characteristics of security groups:

How to Create an AWS Security Group in CloudFormation

Mon, 22 Nov 2021 00:05:00 +0000

Below is a simple CloudFormation script block to create a Security Group in AWS.

Resources:
  SampleAppAppstreamSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Inbound and outbound traffic for service
      GroupName: 'sampleappsg-123'
      VpcId: !Ref vpcid
      Tags:
        - Key: "Name"
          Value: "Sample App Security Group"
      SecurityGroupEgress:
      - IpProtocol: "-1"
        FromPort: 0
        ToPort: 0
        CidrIp: 10.0.0.0/8
      SecurityGroupIngress:
      - IpProtocol: "-1"
        FromPort: 0
        ToPort: 0
        CidrIp: 10.0.0.0/8

You can read up more about all the possible arguments in the AWS Security Group CloudFormation Reference.

How to provide Default Values for AWS CloudFormation Parameters

Sun, 21 Nov 2021 00:05:00 +0000

AWS CloudFormation is very useful for creating template-able infrastructure definitions.

One of the sections of a template, is the Input Parameters, or simply Parameters as CloudFormation calls it. This is a section block that llows for user defined variables to be consumed by the template.

When testing, it can be useful to specify default values here.

This can be achieved by adding the Default key and setting a value.

Parameters:

  environment:
    Type: String
    Default: DEV
  vpcid:
    Type: String
    Default: "vpc-123456789123456a"

How to Validate an AWS CloudFormation Template

Sat, 20 Nov 2021 00:05:00 +0000

The AWS CLI comes with a useful subcommand to validate a CloudFormation template.

Simply run the following to validate a CloudFormation template file:

aws cloudformation validate-template --template-body file://cf-infra.yaml

Remember to swap out cf-infra.yaml with your CloudFormation template file.

How to Reverse Sort Integers in Go

Fri, 19 Nov 2021 00:05:00 +0000

The challenge

The two oldest ages function/method needs to be completed. It should take an array of numbers as its argument and return the two highest numbers within the array. The returned value should be an array in the format [second oldest age, oldest age].

The order of the numbers passed in could be any order. The array will always include at least 2 items. If there are two or more oldest age, then return both of them in array format.

How to view the Encoded Authorization Failure Message in AWS

Thu, 18 Nov 2021 00:05:00 +0000

You may come across a message that reads similar to the following:

<meta charset="utf-8">Encoded authorization failure message

A full message, will look something like:

API: ec2:CreateSecurityGroup You are not authorized to perform this operation. Encoded authorization failure message: B2UTpuAS30_naB5rE3Dw5v2ENy-V5w3H0wmt6rfE8hrpUz2dCIiA5XcBCtzo4cipk_JiGxAKCvlZQy0Rr2Xi3Fg2pKdkvojgn5LOZJzVroFPqMbyJguCJWxxxxxxxDNOZGGGlT2PIxTnqLQ561_piXzApfRL2kv-cYhxnuNwJWEeX8-N15mDcswhUyoV5pYtehdupp5umWZt8mcAiatlf7JIo0Q6tobs7Iw22tWTofMIZW-qkPtrTg7YrrY2--kTF3Q9qQBJw6gjr_QGznd9Fh0OMF_dCLC70bLRg5Jtxn5HyLxZWu9sC-y6x1tebYRokj32NVqr4h8pklocEKe6iqM88xV1cHJXcstP_gvoFf22yFmIll7DcE5Llsn-lD6bsB0QWWgy81m6_X0JW6s5ea4BD2nE1GM511BS20x-gGM65fm5z2SrjU09G-kmXngugnra135eY28qqjdvIl1Knb-KnEXzrtAj_DaAehx5HizwtIdi3_Yxxxxxxx_AmwgLBDZuqEL1BLZjClw7TtVjysGeO6WJyL2NMXN7Gtvzg2AL4q_z-ROH1xxxxxxxxxxx

How to view the Encoded Message from AWS

In your terminal/commandline, you need to paste the encoded message from above (your own one) into the following aws sts tool:

aws sts decode-authorization-message --encoded-message <past_encoded_string_here> --query DecodedMessage --output text | jq '.'

If it complains about jq; perhaps you don’t have it installed; then you can exclude the last section and rather use the following:

How to run/execute a program from Terraform

Wed, 17 Nov 2021 00:05:00 +0000

If you need to run a local application from your Terraform scripts, you can call out to the provisioner local-exec and issue the command syntax:

resource "null_resource" "dig-aoms" {
  provisioner "local-exec" {
    # define your command below
    # this can be any application available in your terminal/commandline, 
    # along with arguments
    command = "dig any andrewodendaal.com"
  }
}

How to script AWS AppStream 2.0 ImageBuilder

Tue, 16 Nov 2021 00:05:00 +0000

AppStream (2.0) is a fully managed non-persistent desktop and application service for remotely accessing your work.

The ImageBuilder forms the first stage in the creation and definition of an image that can be used to stream.

You can use the AWS CLI to initiate the creation of an image in ImageBuilder:

aws appstream create-image-builder \
  --name <name> \
  --image-name <image_name> \
  --instance-type <instance_type> \
  --vpc-config SubnetIds=<subnet_ids>,SecurityGroupIds=<security_group_ids> \
  --iam-role-arn <iam_role_arn> \
  --enable-default-internet-access

Swap out the above items with your own values:

How to Reimplement the Unix Uniq Command in Golang

Mon, 15 Nov 2021 00:05:00 +0000

The challenge

Implement a function which behaves like the uniq command in UNIX.

It takes as input a sequence and returns a sequence in which all duplicate elements following each other have been reduced to one instance.

Example:

["a", "a", "b", "b", "c", "a", "b", "c"]  =>  ["a", "b", "c", "a", "b", "c"]

The solution in Golang

Option 1:

package uniq
func Uniq(a []string) []string {
 array := []string{}
  for i, value := range a {
    if i == 0 {
      array = append(array, value)
    } else if a[i-1] != value {
      array = append(array, value)
    }
  }
  return array
}

Option 2:

How to install GraalVM on Mac

Sun, 14 Nov 2021 00:05:00 +0000

Install GraalVM with Homebrew

Homebrew is the preferred way to install anything on your Mac.

brew install graalvm/tap/graalvm-ce-java17

Install GraalVM without Homebrew

Follow these 5 steps to get GraalVM installed on your Mac.

Step1:

Download the official binary: https://www.graalvm.org/downloads/

Unpack the archive into a folder.

Step2:

Move the folder into the JavaVirtualMachines directory:

sudo mv graalvm-ce-java17-21.3.0 /Library/Java/JavaVirtualMachines

sudo is required because /Library is a system directory.

Step3:

Verify the installation using the java_home utility:

How to Generate Random Integers with a Range in Java

Sat, 13 Nov 2021 00:05:00 +0000

Java comes with many different ways to generate random integers, even if you need to specify a lower and upper bound to constrain your required value for.

Option 1 – ThreadLocalRandom

Specify the min and max values:

import java.util.concurrent.ThreadLocalRandom;

int randomNum = ThreadLocalRandom.current().nextInt(min, max + 1);

Option 2 – Random

Between `` (inclusive) and the specified value (exclusive):

import java.util.Random;

Random rn = new Random();
int range = maximum - minimum + 1;
int randomNum =  rn.nextInt(range) + minimum;

Option 3 – Multiple values

import java.util.Random;

Random r = new Random();
int[] fiveRandomNumbers = r.ints(5, 0, 11).toArray();
int randomNumber = r.ints(1, 0, 11).findFirst().getAsInt();

How to create ArrayList from Array in Java

Fri, 12 Nov 2021 00:05:00 +0000

The problem

If you have a traditional array, that looks something like the following:

A[] array = {new A(1), new A(2), new A(3)};

And you would like to convert this to an ArrayList:

ArrayList<Element> arraylist = ???;

..then you can do the following!

The solution

The technique

new ArrayList<>(Arrays.asList(array));

How to use it

Of course you could always simplify this one further directly as:

List<ClassName> list = Arrays.asList(array)

How to old Java

If you are stuck in the old world of Java, you can fall back to:

How to Generate a Random AlphNumeric String in Linux/MacOS

Thu, 11 Nov 2021 00:05:00 +0000

If you need to generate a random AlphaNumeric string from the Linux/MacOS Command-Line, then you can use the following script:

dd if=/dev/random bs=8 count=1 2>/dev/null | od -An -tx1 | tr -d ' \t\n'

This can also be piped into a variable as follows:

RANDOM_ID=$(dd if=/dev/random bs=8 count=1 2>/dev/null | od -An -tx1 | tr -d ' \t\n')

The above echo $RANDOM_ID will resemble something similar to: 90fa3bb51922eadc

How to check if a string is empty in Go

Wed, 10 Nov 2021 00:05:00 +0000

If you need to check if a string is empty in Go, then there are two possible ways to immediately verify this:

Option 1 – Compare the length:

if len(s) > 0 {
    // do something with string
}

Option 2 – Compare against blank:

if s != "" {
    // do something with string
}

How to read a file line by line in Go

Tue, 09 Nov 2021 00:05:00 +0000

If you need to read a file line by line in Go, then you can use the bufio package as follows:

package main
import (
    "bufio"
    "fmt"
    "log"
    "os"
)
func main() {
    file, err := os.Open("/path/to/file.txt")
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()
    scanner := bufio.NewScanner(file)
    for scanner.Scan() {
        fmt.Println(scanner.Text())
    }
    if err := scanner.Err(); err != nil {
        log.Fatal(err)
    }
}

Just note that the Scanner will throw an error if any line has a character count longer than 65536. This relates back to a 64K size limit. In this case, you can use the Buffer method to increase the capacity.

Floating-point Approximation in Golang

Mon, 08 Nov 2021 00:05:00 +0000

The challenge

Consider the function

f: x -> sqrt(1 + x) - 1 at x = 1e-15.

We get: f(x) = 4.44089209850062616e-16

This function involves the subtraction of a pair of similar numbers when x is near 0 and the results are significantly erroneous in this region. Using pow instead of sqrt doesn’t give better results.

A “good” answer is 4.99999999999999875... * 1e-16.

Can you modify f(x) to give a good approximation of f(x) in the neighborhood of 0?

All the Ways to Divide an Array in Two in Golang

Sun, 07 Nov 2021 00:05:00 +0000

The challenge

Write a function partlist that gives all the ways to divide an array of at least two elements into two non-empty parts.

Each two non empty parts will be in a pair
Each part will be in a string
Elements of a pair must be in the same order as in the original array.

Examples:

a = ["az", "toto", "picaro", "zone", "kiwi"] -->
[("az", "toto picaro zone kiwi"), ("az toto", "picaro zone kiwi"), ("az toto picaro", "zone kiwi"), ("az toto picaro zone", "kiwi")]

The solution in Golang

Option 1:

How to check if a file exists in Go

Sat, 06 Nov 2021 00:05:00 +0000

If you need to check if a file exists using Go, then you can use one of the following methods, depending on the version of Go you may be using.

If you are using Go >=1.13, then

file, err := os.OpenFile("/path/to/file.txt")
if errors.Is(err, os.ErrNotExist) {
    // The file does not exists
}

However, it is also possible to trap an error from an OpenFile attempt:

file, err := os.OpenFile("/path/to/file.txt")
if os.IsNotExist(err) {
    // The file does not exists
}

You can also confirm if the path is also not a directory as follows:

How to convert a string value to an int in Go

Fri, 05 Nov 2021 00:05:00 +0000

If you need to convert a string to an int in Go, then you should use the strconv.Atoi function:

package main
import (
    "strconv"
    "fmt"
)
func main() {
    t := strconv.Atoi("123")
    fmt.Println(t)
}

Learn how to convert an int value to a string in Go.

How to convert an int value to string in Go

Thu, 04 Nov 2021 00:05:00 +0000

If you need to convert an int to a string in Go, then you should use the strconv.Itoa function:

package main
import (
    "strconv"
    "fmt"
)
func main() {
    t := strconv.Itoa(123)
    fmt.Println(t)
}

Learn how to convert a string value to an int in Go.

How to Efficiently Concatenate Strings in Go

Wed, 03 Nov 2021 00:05:00 +0000

If you are using a version of Go >= 1.10, then you should be using the newer strings.Builder pattern as follows:

package main
import (
    "strings"
    "fmt"
)
func main() {
    var sb strings.Builder
    for i := 0; i < 100; i++ {
        sb.WriteString("a")
    }
    fmt.Println(sb.String())
}

For older version, you should be looking to use the bytes.Buffer instead:

package main
import (
    "bytes"
    "fmt"
)
func main() {
    var buffer bytes.Buffer
    for i := 0; i < 100; i++ {
        buffer.WriteString("a")
    }
    fmt.Println(buffer.String())
}

How to check if a map contains a key in Go

Tue, 02 Nov 2021 00:05:00 +0000

If you have a map in Go and want to only perform an action if it contains a certain key, then you can do so easily:

if val, ok := myMap["someValue"]; ok {
    // your code here
}

The way this works is the conditional if statement checks to see if a value of someValue exists in the myMap map variable.

If it exists, it assigns the key’s value to a val variable, and assigns the ok variable to a truthy boolean.

How to Remove all Vowels from a String in Java

Mon, 01 Nov 2021 00:05:00 +0000

The challenge

Remove all vowels from the string.

Vowels:

a e i o u
A E I O U

The solution in Java code

Option 1:

public class VowelRemoval {
  public static String disemvowel(String str) {
      return str.replaceAll("[aAeEiIoOuU]", "");
  } 
}

Option 2:

public class VowelRemoval {
    public static String disemvowel(String str) {
        return str.replaceAll("(?i)[aeiou]" , "");
    }
}

Option 3:

public class VowelRemoval {
    public static String disemvowel(String str) {
        return str
          .replaceAll("a", "").replaceAll("A", "")
          .replaceAll("e", "").replaceAll("E", "")
          .replaceAll("i", "").replaceAll("I", "")
          .replaceAll("o", "").replaceAll("O", "")
          .replaceAll("u", "").replaceAll("U", "");
    }
}

Test cases to validate our solution

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.lang.StringBuilder;
import java.util.Random;
public class Tests {
    @Test
    public void FixedTests() {
        assertEquals("Ths wbst s fr lsrs LL!" ,
                    VowelRemoval.disemvowel("This website is for losers LOL!"));
        assertEquals("N ffns bt,\nYr wrtng s mng th wrst 'v vr rd",
                VowelRemoval.disemvowel
                ("No offense but,\nYour writing is among the worst I've ever read"));
        assertEquals("Wht r y,  cmmnst?" , VowelRemoval.disemvowel("What are you, a communist?"));
    }
    public static String generateRandomChars(String candidateChars, int length) {
        StringBuilder sb = new StringBuilder();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(candidateChars.charAt(random.nextInt(candidateChars.length())));
        }
        return sb.toString();
    }
    public static String C(String Z) {
        return Z.replaceAll("(?i)[aeiou]" , "");
    }
    @Test
    public void RandomTests() {
        for(int i = 0; i < 100; i++) {
            String X = generateRandomChars(
                "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", i + 3);
            assertEquals(C(X) , VowelRemoval.disemvowel(X));
        }
    }
}

How to Loop Forever in Golang

Sun, 31 Oct 2021 00:05:00 +0000

If you need to loop forever, or infinitely, in your Go code, then you have 2 options:

Option 1:

for {
  // your code here
}

Option 2:

for true {
  // your code here
}

Just remember that you need to break out of this, otherwise it really will run forever!

How to use in a Go Application

package main

func main() {

  // OPTION 1
  for {
    // your code here
  }

  // OPTION 2
  for true {
    // your code here
  }

}

Understanding For Loops in Golang

Sat, 30 Oct 2021 00:05:00 +0000

In Golang a for loop is a way to loop through an iterable.

The most basic For Loop

i := 0
for i <= 3 {
  i = i + 1
}

A classic For Loop

for i := 7; i <= 9; i++ {
  // do something
}

For Loop without Conditions

A for without a condition will loop forever, until either a break or return is hit.

for {
  // do something
  break // kill the loop
}

When to use `continue`

A continue will move to the next iteration of the loop

[Solved] go mod init: modules disabled by GO111MODULE=off

Fri, 29 Oct 2021 00:05:00 +0000

You’ve probably just tried to initialise a new Go module, and received the following error:

go mod init: modules disabled by GO111MODULE=off; see 'go help modules'

This usually happens after running a command like:

go mod init github.com/<user>/<repo>

What is GO111MODULE?

From Go version 1.11, the way to deal with modules was revamped.

Beforehand, it was required that you place all your Go code under a $GOPATH.

Which many Go developers didn’t much like, as it seemed chaotic at best.

How to UpperCase the start of each Word in a String in Golang

Thu, 28 Oct 2021 00:05:00 +0000

The challenge

The task is to take a string of lower-cased words and convert the sentence to upper-case the first letter/character of each word

Example:

this is the sentence would be This Is The Sentence

The solution in Golang

Option 1:

As a first approach, we could loop through each word, and Title it before adding it back to a new string. Then make sure to trim any spaces before returning it.

How to Solve Max-Min Arrays in Java

Wed, 27 Oct 2021 00:05:00 +0000

The challenge

You are given an array of unique elements, and your task is to rearrange the values so that the first max value is followed by the first minimum, followed by second max value then second min value, etc.

For example:

solve([15,11,10,7,12]) = [15,7,12,10,11]

The first max is 15 and the first min is 7. The second max is 12 and the second min is 10 and so on.

The solution in Java code

Option 1:

How to Find the Smallest Integer in the Array in Golang

Tue, 26 Oct 2021 00:22:14 +0000

The challenge

Given an array of integers your solution should find the smallest integer.

For example:

Given [34, 15, 88, 2] your solution will return 2
Given [34, -345, -1, 100] your solution will return -345

You can assume, for the purpose of this challenge, that the supplied array will not be empty.

The solution in Golang

Option 1:

package solution
func SmallestIntegerFinder(numbers []int) int {
  curr := numbers[0]
  for _, v := range numbers {
    if v<curr {
      curr = v
    }
  }
  return curr
}

Option 2:

How to do Basic Encryption in Java

Mon, 25 Oct 2021 00:05:00 +0000

The challenge

The most basic encryption method is to map a char to another char by a certain math rule. Because every char has an ASCII value, we can manipulate this value with a simple math expression. For example ‘a’ + 1 would give us ‘b’, because ‘a’ value is 97 and ‘b’ value is 98.

You will need to write a method that does exactly that –

get a string as text and an int as the rule of manipulation, and should return encrypted text. for example:

Forming Unique Array Combinations in Golang

Sun, 24 Oct 2021 00:05:00 +0000

The challenge

You are given an array of arrays and your task will be to return the number of unique arrays that can be formed by picking exactly one element from each subarray.

For example: solve([[1,2],[4],[5,6]]) = 4, because it results in only 4 possibilites. They are [1,4,5],[1,4,6],[2,4,5],[2,4,6].

Make sure that you don’t count duplicates; for example solve([[1,2],[4,4],[5,6,6]]) = 4, since the extra outcomes are just duplicates.

The solution in Golang

Option 1:

How to Check if String is a Palindrome in Python

Sat, 23 Oct 2021 00:05:00 +0000

The challenge

Write a function that checks if a given string (case insensitive) is a palindrome.

The solution in Python

Option 1:

def is_palindrome(s):
    s = s.lower()
    for i, item in enumerate(s):
        if i<len(s)/2:
            if s[i]!=s[len(s)-i-1]:
                return False
    return True

Option 2:

def is_palindrome(s):
    s = s.lower()
    return s == s[::-1]

Option 3:

def is_palindrome(s):
    return s.lower()==s[::-1].lower()

Test cases to validate our solution

@test.describe('sample tests')
def sample_tests():
    test.assert_equals(is_palindrome('a'), True)
    test.assert_equals(is_palindrome('aba'), True)
    test.assert_equals(is_palindrome('Abba'), True)
    test.assert_equals(is_palindrome('malam'), True)
    test.assert_equals(is_palindrome('walter'), False)
    test.assert_equals(is_palindrome('kodok'), True)
    test.assert_equals(is_palindrome('Kasue'), False)

How to Find the Squares in Java

Fri, 22 Oct 2021 00:05:00 +0000

The challenge

Complete the function that takes an odd integer (0 < n < 1000000) which is the difference between two consecutive perfect squares, and return these squares as a string in the format "bigger-smaller".

9  -->  "25-16"
5  -->  "9-4"
7  -->  "16-9"

The solution in Java code

Option 1:

public class Solution {
  public static String findSquares(final int n) {
    final long a = (n + 1) / 2;
    final long b = a - 1;
    return String.format("%d-%d", a * a, b * b);
  }
}

Option 2:

How to Get Longest Word in Sentence in Java

Thu, 21 Oct 2021 00:05:00 +0000

The challenge

When given a string of space-separated words, return the word with the longest length.

If there are multiple words with the longest length, return the last instance of the word with the longest length.

Example:

'red white blue' // returns string value of white
'red blue gold'  // returns gold

The solution in Java code

Option 1:

public class Solution {
  public static String longestWord(String wordString) {
    String longest = "";
    for (String word: wordString.split(" "))
      if (word.length()>=longest.length())
        longest = word;
    return longest;
  }
}

Option 2:

How to Sum all the Integers in a String in Golang

Wed, 20 Oct 2021 00:05:00 +0000

The challenge

Implement a function that calculates the sum of the integers inside a string. For example, in the string "The30quick20brown10f0x1203jumps914ov3r1349the102l4zy dog", the sum of the integers is 3635.

Note: only positive integers will be tested.

The solution in Golang

Option 1:

package solution
import (
  "fmt"
  "regexp"
  "strconv"
)
func SumOfIntegersInString(strng string) int {
  re := regexp.MustCompile("[0-9]+")
  fmt.Println(re.FindAllString(strng, -1))
  sum := 0
  for _, i := range re.FindAllString(strng, -1) {
    number, _ := strconv.Atoi(i)
    sum += number
  }
  return sum
}

Option 2:

How to Reverse a String in Golang

Tue, 19 Oct 2021 00:05:00 +0000

The challenge

Complete the solution so that it reverses the string passed into it.

'world'  =>  'dlrow'
'word'   =>  'drow'

The solution in Golang

Option 1:

package solution
func Solution(word string) (out string) {
  for _, v := range word {
    out = string(v) + out
  }
  return
}

Option 2:

package solution
import "strings"
func Solution(word string) string {    
    var b strings.Builder
    for i:=len(word)-1; i>-1; i-- {
      b.WriteByte(word[i])      
    }
    return b.String()
}

Option 3:

Maximum Different of Int-Array in Java

Mon, 18 Oct 2021 00:05:00 +0000

The challenge

You must implement a function that returns the difference between the biggest and the smallest value in a list(lst) received as a parameter.

The list(lst) contains integers, which means it may contain some negative numbers.

If the list is empty or contains a single element, return 0.

The list(lst) is not sorted.

maxDiff([1, 2, 3, 4]); // return 3, because 4 - 1 == 3
maxDiff([1, 2, 3, -4]); // return 7, because 3 - (-4) == 7

The solution in Java code

Option 1:

Indexed Capitalization in Java

Sun, 17 Oct 2021 00:05:00 +0000

The challenge

Given a string and an array of integers representing indices, capitalize all letters at the given indices.

Example:

capitalize("abcdef",[1,2,5]) = "aBCdeF"
capitalize("abcdef",[1,2,5,100]) = "aBCdeF". There is no index 100.

The input will be a lowercase string with no spaces and an array of digits.

The solution in Java code

Option 1:

package solution;

import java.util.*;

public class Solution{
    public static String capitalize(String s, int[] ind){
        char[] chars = s.toCharArray();
        Arrays.stream(ind)
                .filter(c -> c < s.length())
                .forEach(c -> chars[c] = Character.toUpperCase(chars[c]));
        return new String(chars);
    }
}

Option 2:

How to Spacify a String in Java

Sat, 16 Oct 2021 00:05:00 +0000

The challenge

Modify the spacify function so that it returns the given string with spaces inserted between each character.

spacify("hello world") // returns "h e l l o   w o r l d"

The solution in Java code

Option 1:

import java.util.*;
import java.util.stream.*;

public class Spacify {
    public static String spacify(String str){
        return Arrays.stream(str.split(""))
                .map(c -> c+" ")
                .collect(Collectors.joining())
                .trim();
    }
}

Option 2:

public class Spacify {
    public static String spacify(String str){
        return str.replaceAll("", " ").trim();
    }
}

Option 3:

How to Find the Last Digit of a Huge Number in Golang

Fri, 15 Oct 2021 01:47:38 +0000

The challenge

For a given list [x1, x2, x3, ..., xn] compute the last (decimal) digit of x1 ^ (x2 ^ (x3 ^ (... ^ xn))).

Example:

last_digit({3, 4, 2}, 3) == 1

because 3 ^ (4 ^ 2) = 3 ^ 16 = 43046721.

Beware: powers grow incredibly fast. For example, 9 ^ (9 ^ 9) has more than 369 millions of digits. lastDigit has to deal with such numbers efficiently.

Find the Maximum Length Difference between Lists/Arrays in Python

Thu, 14 Oct 2021 00:05:00 +0000

The challenge

You are given two arrays a1 and a2 of strings. Each string is composed of letters from a to z. Let x be any string in the first array and y be any string in the second array.

Find max(abs(length(x) − length(y)))

If a1 and/or a2 are empty return -1 in each language except in Haskell (F#) where you will return Nothing (None).

a1 = ["hoqq", "bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"]
a2 = ["cccooommaaqqoxii", "gggqaffhhh", "tttoowwwmmww"]
mxdiflg(a1, a2) --> 13

The solution in Python

Option 1:

How to Circularly Sort an Array in Golang

Wed, 13 Oct 2021 00:05:00 +0000

The challenge

An array is circularly sorted if the elements are sorted in ascending order but displaced, or rotated, by any number of steps.

Complete the function/method that determines if the given array of integers is circularly sorted.

These arrays are circularly sorted (true):

[2, 3, 4, 5, 0, 1]       -->  [0, 1] + [2, 3, 4, 5]
[4, 5, 6, 9, 1]          -->  [1] + [4, 5, 6, 9]
[10, 11, 6, 7, 9]        -->  [6, 7, 9] + [10, 11]
[1, 2, 3, 4, 5]          -->  [1, 2, 3, 4, 5]
[5, 7, 43, 987, -9, 0]   -->  [-9, 0] + [5, 7, 43, 987]
[1, 2, 3, 4, 1]          -->  [1] + [1, 2, 3, 4]

While these are not (false):

Largest Number Groupings in String in Python

Tue, 12 Oct 2021 00:05:00 +0000

The challenge

You are be given a string that has lowercase letters and numbers. Your task is to compare the number groupings and return the largest number. Numbers will not have leading zeros.

For example, solve("gh12cdy695m1") = 695, because this is the largest of all number groupings.

The solution in Python code

Option 1:

import re
def solve(s):
    return max(map(int,re.findall(r"(\d+)", s)))

Option 2:

def solve(s):
    return max(map(int,"".join(" " if x.isalpha() else x for x in s).split()))

Option 3:

How to Alternate String Casing in Golang

Mon, 11 Oct 2021 00:50:04 +0000

The challenge

Write a function toWeirdCase (weirdcase in Ruby) that accepts a string, and returns the same string with all even indexed characters in each word uppercased, and all odd indexed characters in each word lowercased. The indexing just explained is zero-based, so the zero-ith index is even, therefore that character should be uppercased and you need to start over for each word.

The passed-in string will only consist of alphabetical characters and spaces(' '). Spaces will only be present if there are multiple words. Words will be separated by a single space(' ').

How to Sort a List of Numbers in Python

Sun, 10 Oct 2021 00:18:34 +0000

The challenge

Finish the solution so that it sorts the passed-in array/list of numbers. If the function passes in an empty array/list or null/None value then it should return an empty array/list.

Examples:

solution([1,2,3,10,5]) # should return [1,2,3,5,10]
solution(None) # should return []

The solution in Python code

Option 1:

def solution(nums):
    if not nums:
        return []
    return sorted(nums)

Option 2:

def solution(nums):
    return sorted(nums) if nums else []

Option 3:

def solution(nums):
    return sorted(nums or [])

Test cases to validate our solution

import test
from solution import solution

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(solution([1,2,3,10,5]), [1,2,3,5,10])
        test.assert_equals(solution(None), [])
        test.assert_equals(solution([]), [])
        test.assert_equals(solution([20,2,10]), [2,10,20])
        test.assert_equals(solution([2,20,10]), [2,10,20])

How to Validate Usernames with Regex in Java

Sat, 09 Oct 2021 00:05:00 +0000

The challenge

Write a simple regex to validate a username. Allowed characters are:

lowercase letters,
numbers,
underscore

Length should be between 4 and 16 characters (both included).

The solution in Java code

Option 1:

public class PasswordValidation {
  public static boolean validateUsr(String s) {
    return s.matches("[a-z_\\d]{4,16}");
  }
}

Option 2:

import java.util.regex.Pattern;
public class PasswordValidation {
  private static final Pattern usernamePattern = 
      Pattern.compile("[a-z0-9_]{4,16}");
  public static boolean validateUsr(String s) {
    return usernamePattern.matcher(s).matches();
  }
}

Option 3:

Sort Lexicographical Order of Substrings in Java

Fri, 08 Oct 2021 00:05:00 +0000

The challenge

Given two arrays of strings a1 and a2 return a sorted array r in lexicographical order of the strings of a1 which are substrings of strings of a2.

a1 = ["arp", "live", "strong"]

a2 = ["lively", "alive", "harp", "sharp", "armstrong"]

returns ["arp", "live", "strong"]

a1 = ["tarp", "mice", "bull"]

a2 = ["lively", "alive", "harp", "sharp", "armstrong"]

returns []

How to Perform Alphabetical Addition in Java

Thu, 07 Oct 2021 00:05:00 +0000

The challenge

Your task is to add up letters to one letter.

The function will be given an array of single-character Strings, each one being a letter to add.

Letters will always be lowercase.
Letters can overflow (see second to last example of the description)
If no letters are given, the function should return 'z'

addLetters("a", "b", "c") = "f"
addLetters("a", "b") = "c"
addLetters("z") = "z"
addLetters("z", "a") = "a"
addLetters("y", "c", "b") = "d" // notice the letters overflowing
addLetters() = "z"

The solution in Java code

Option 1:

Roman Numerals Decoder in Golang

Wed, 06 Oct 2021 00:05:00 +0000

The challenge

Create a function that takes a Roman numeral as its argument and returns its value as a numeric decimal integer. You don’t need to validate the form of the Roman numeral.

Modern Roman numerals are written by expressing each decimal digit of the number to be encoded separately, starting with the leftmost digit and skipping any 0s. So 1990 is rendered “MCMXC” (1000 = M, 900 = CM, 90 = XC) and 2008 is rendered “MMVIII” (2000 = MM, 8 = VIII). The Roman numeral for 1666, “MDCLXVI”, uses each letter in descending order.

How to Subtract from Time in Golang

Tue, 05 Oct 2021 00:05:00 +0000

The challenge

Clock shows h hours, m minutes and s seconds after midnight.

Your task is to write a function that returns the time since midnight in milliseconds.

h = 0
m = 1
s = 1

result = 61000

Input constraints:

0 <= h <= 23
0 <= m <= 59
0 <= s <= 59

The solution in Golang

Option 1:

package solution
func Past(h, m, s int) int {
    return (h*3600000 + m*60000 + s*1000)    
}

Option 2:

How to Encrypt Words in Java

Mon, 04 Oct 2021 00:05:00 +0000

The challenge

You want to create secret messages which must be deciphered.

Here are the conditions:

Your message is a string containing space separated words.
You need to encrypt each word in the message using the following rules:
- The first letter must be converted to its ASCII code.
- The second letter must be switched with the last letter
Keepin’ it simple: There are no special characters in the input.

EncryptWords.encryptThis("Hello") => "72olle"
EncryptWords.encryptThis("good") => "103doo"
EncryptWords.encryptThis("hello world") => "104olle 119drlo"

The solution in Java code

Option 1:

Bit Counting in Golang

Sun, 03 Oct 2021 03:22:47 +0000

The challenge

Write a function that takes an integer as input, and returns the number of bits that are equal to one in the binary representation of that number. You can guarantee that input is non-negative.

Example: The binary representation of 1234 is 10011010010, so the function should return 5 in this case

The solution in Golang

Option 1:

package solution
import "math/bits"
func CountBits(n uint) int {
  return bits.OnesCount(n)
}

Option 2:

How to Find Next Higher Number with Same Bits in Golang

Sat, 02 Oct 2021 00:38:52 +0000

The challenge

Find the next higher number (int) with same ‘1’- Bits.

I.e. as much 1 bits as before and output next higher than input. Input is always an int in between 1 and 1«30 (inclusive). No bad cases or special tricks…

Input: 129  => Output: 130 (10000001 => 10000010)
Input: 127 => Output: 191 (01111111 => 10111111)
Input: 1 => Output: 2 (01 => 10)
Input: 323423 => Output: 323439 (1001110111101011111 => 1001110111101101111)

The solution in Golang

Option 1:

How to Find the First Non-Repeating Character in Golang

Fri, 01 Oct 2021 00:50:38 +0000

The challenge

Write a function named first_non_repeating_letter that takes a string input, and returns the first character that is not repeated anywhere in the string.

For example, if given the input 'stress', the function should return 't', since the letter t only occurs once in the string, and occurs first in the string.

As an added challenge, upper- and lowercase letters are considered the same character, but the function should return the correct case for the initial letter. For example, the input 'sTreSS' should return 'T'.

How to Find the Last Fibonacci Digit in Golang

Thu, 30 Sep 2021 01:19:01 +0000

The challenge

Return the last digit of the nth element in the Fibonacci sequence (starting with 1,1, to be extra clear, not with 0,1 or other numbers).

LastFibDigit(1) == 1
LastFibDigit(2) == 1
LastFibDigit(3) == 2
LastFibDigit(1000) == 5
LastFibDigit(1000000) == 5

The solution in Golang

Option 1:

package solution
func LastFibDigit(n int) int {
  n %= 60
  a, b := 0, 1
  for i := 0; i<n; i++ { a, b = b, a+b }
  return a % 10
}

Option 2:

How to Validate an IP Address in Golang

Wed, 29 Sep 2021 01:31:02 +0000

The challenge

Write an algorithm that will identify valid IPv4 addresses in dot-decimal format. IPs should be considered valid if they consist of four octets, with values between `` and 255, inclusive.

1.2.3.4
123.45.67.89

1.2.3
1.2.3.4.5
123.456.78.90
123.045.067.089

Leading zeros (e.g. 01.02.03.04) are considered invalid
Inputs are guaranteed to be a single string

The solution in Golang

Option 1:

How to Fold an Array in Java

Tue, 28 Sep 2021 03:18:38 +0000

The challenge

In this challenge, you have to write a method that folds a given array of integers by the middle x-times.

An example says more than a thousand words:

Fold 1-times:
[1,2,3,4,5] -> [6,6,3]

A little visualization (NOT for the algorithm but for the idea of folding):

 Step 1         Step 2        Step 3       Step 4       Step5
                     5/           5|         5\          
                    4/            4|          4\      
1 2 3 4 5      1 2 3/         1 2 3|       1 2 3\       6 6 3
----*----      ----*          ----*        ----*        ----*


Fold 2-times:
[1,2,3,4,5] -> [9,6]

As you see, if the count of numbers is odd, the middle number will stay. Otherwise, the fold-point is between the middle-numbers, so all numbers would be added in a way.

Formatting Strings with Fmt in Golang

Mon, 27 Sep 2021 03:08:03 +0000

Fmt provides printing to standard output (usually the console) and formatting of strings capabilities.

The basics of Print and Println

The main difference between fmt.Print and fmt.Println is that you only get a newline/carriage return by default with the second one. Other than that, you can make use of either for string formatting.

Firstly, we need to import the fmt module as follows:

package main

import "fmt" // <--- include fmt

func main() {
    // main
}

Example of fmt.Print

fmt.Print("This is a Print test")

// "This is a Print test"

This will print to standard output without a newline at the end.

Delete Occurrences of an Element if it occurs more than N times in Java

Sun, 26 Sep 2021 00:05:00 +0000

The challenge

Given a list lst and a number N, create a new list that contains each number of lst at most N times without reordering. For example if N = 2, and the input is [1,2,3,1,2,1,2,3], you take [1,2,3,1,2], drop the next [1,2] since this would lead to 1 and 2 being in the result 3 times, and then take 3, which leads to [1,2,3,1,2,3].

// return [20,37,21]
EnoughIsEnough.deleteNth(new int[] {20,37,20,21}, 1)

// return [1, 1, 3, 3, 7, 2, 2, 2]
EnoughIsEnough.deleteNth(new int[] {1,1,3,3,7,2,2,2,2}, 3)

The solution in Java code

Option 1:

How to Read from Standard Input in Golang

Sat, 25 Sep 2021 12:53:50 +0000

Reading from “standard input” is really useful if you are making a command-line application and require user input.

package main

import (
    "bufio"
    "os"
    "fmt"
)

func main() {
    reader := bufio.NewReader(os.Stdin)
    s, _ := reader.ReadString('\n')
    fmt.Printf(s)
}

First setup a new bufio reader, then use ReadString function, with a default wait character, which we have set to a newline (\n).

The application will pause at this point and wait for user input before proceeding.

How to Install Golang on WSL/WSL2

Fri, 24 Sep 2021 00:05:00 +0000

If you need to install Golang on WSL under Windows 10 or higher, you can follow these few steps.

First remove any old versions lying around

sudo rm -rf /usr/local/go* && sudo rm -rf /usr/local/go

Determine the latest Go version

Go to https://golang.org/dl/ and find out what the latest version is. At the time of writing this, Go is on version 1.16.

Install Go

Make sure to replace 1.16 below with the updated version as required.

How to Validate Phone Numbers in Java

Thu, 23 Sep 2021 00:05:00 +0000

The challenge

Write a function that accepts a string, and returns true if it is in the form of a phone number.
Assume that any integer from 0-9 in any of the spots will produce a valid phone number.

Only worry about the following format:
(123) 456-7890 (don’t forget the space after the close parentheses)

Examples:

"(123) 456-7890"  => true
"(1111)555 2345"  => false
"(098) 123 4567"  => false

The solution in Java code

Option 1:

How to Sort Array by Frequency in Java

Wed, 22 Sep 2021 01:32:33 +0000

The challenge

Sort elements in an array by decreasing frequency of elements. If two elements have the same frequency, sort them by increasing value.

Solution.sortByFrequency(new int[]{2, 3, 5, 3, 7, 9, 5, 3, 7});
// Returns {3, 3, 3, 5, 5, 7, 7, 2, 9}
// We sort by highest frequency to lowest frequency.
// If two elements have same frequency, we sort by increasing value.

The solution in Java code

Option 1:

How to Calculate String Rotation in Java

Tue, 21 Sep 2021 00:04:40 +0000

The challenge

Write a function that receives two strings and returns n, where n is equal to the number of characters we should shift the first string forward to match the second. The check should be case-sensitive.

For instance, take the strings “fatigue” and “tiguefa”. In this case, the first string has been rotated 5 characters forward to produce the second string, so 5 would be returned. If the second string isn’t a valid rotation of the first string, the method returns -1.

Compare Strings by Sum of Chars in Java

Mon, 20 Sep 2021 00:05:00 +0000

The challenge

Compare two strings by comparing the sum of their values (ASCII character code).

For comparing treat all letters as UpperCase
null should be treated as empty strings
If the string contains other characters than letters, treat the whole string as it would be empty

Your method should return true, if the strings are equal and false if they are not equal.

Examples:

"AD", "BC"  -> equal
"AD", "DD"  -> not equal
"gf", "FG"  -> equal
"zz1", ""   -> equal (both are considered empty)
"ZzZz", "ffPFF" -> equal
"kl", "lz"  -> not equal
null, ""    -> equal

The solution in Java code

Option 1:

How to Add Two Integers Without Arithmetic Operator in Java

Sun, 19 Sep 2021 00:39:48 +0000

The challenge

Given two integers a, b, find The sum of them, BUT You are not allowed to use the operators + and –

The numbers (a,b) may be positive , negative values or zeros .
Returning value will be an integer .
Java: the following methods are prohibited: addExact, average, collect, decrement, increment, nextAfter, nextDown, nextUp, reduce, subtractExact, sum, summing .
The following classes are prohibited: BigDecimal and BigInteger .

1- Add (5,19) ==> return (24) 
2- Add (-27,18) ==> return (-9)
3- Add (-14,-16) ==> return (-30)

The solution in Java code

Option 1:

Counting Method VarArgs in Java

Sat, 18 Sep 2021 00:05:00 +0000

The challenge

Count how many arguments a method is called with.

Examples

args_count(1, 2, 3) -> 3
args_count(1, 2, 3, 10) -> 4

The solution in Java code

Some languages refer to this as the spread operator. In Java, this is called a VarArg, which means a Variable Amount of Arguments.

Simply prepend the argument’s name with three dots (...) and then refer to it like an array of elements.

class Arguments {
  public static int countArgs(Object... args) {
    return args.length;
  }
}

Alternatively, you could also use a stream on it:

How to Sum Consecutives in Java

Fri, 17 Sep 2021 00:05:00 +0000

The challenge

You are given a list/array which contains only integers (positive and negative). Your job is to sum only the numbers that are the same and consecutive. The result should be one list.

Extra credit if you solve it in one line. You can assume there is never an empty list/array and there will always be an integer.

Same meaning: 1 == 1

1 != -1

Examples:

[1,4,4,4,0,4,3,3,1] # should return [1,12,0,4,6,1]

"""So as you can see sum of consecutives 1 is 1 
sum of 3 consecutives 4 is 12 
sum of 0... and sum of 2 
consecutives 3 is 6 ..."""

[1,1,7,7,3] # should return [2,14,3]
[-5,-5,7,7,12,0] # should return [-10,14,12,0]

The solution in Java code

Option 1:

Replacing Occurences of Words in Java

Thu, 16 Sep 2021 00:05:00 +0000

The challenge

You are given a string. You must replace any occurrence of the sequence coverage by covfefe, however, if you don’t find the word coverage in the string, you must add covfefe at the end of the string with a leading space.

The solution in Java code

Option 1:

public class Covfefe {
    public static String covfefe(String tweet) {
        return tweet.contains("coverage") ?
                tweet.replaceAll("coverage", "covfefe") :
                tweet+" covfefe";
    }
}

Option 2:

Convert String to LeetSpeak in Java

Wed, 15 Sep 2021 00:05:00 +0000

The challenge

Your task is to write a function toLeetSpeak that converts a regular english sentence to Leetspeak.

More about LeetSpeak You can read at wiki -> https://en.wikipedia.org/wiki/Leet

Consider only uppercase letters (no lowercase letters, no numbers) and spaces.

For example:

toLeetSpeak("LEET") returns "1337"

In this challenge we use a simple LeetSpeak dialect. Use this alphabet:

{
  A : '@',
  B : '8',
  C : '(',
  D : 'D',
  E : '3',
  F : 'F',
  G : '6',
  H : '#',
  I : '!',
  J : 'J',
  K : 'K',
  L : '1',
  M : 'M',
  N : 'N',
  O : '0',
  P : 'P',
  Q : 'Q',
  R : 'R',
  S : '$',
  T : '7',
  U : 'U',
  V : 'V',
  W : 'W',
  X : 'X',
  Y : 'Y',
  Z : '2'
}

The solution in Java code

Option 1:

Ordered Count of Characters in Python

Tue, 14 Sep 2021 00:05:00 +0000

The challenge

Count the number of occurrences of each character and return it as a list of tuples in order of appearance. For empty output return an empty list.

Example:

ordered_count("abracadabra") == [('a', 5), ('b', 2), ('r', 2), ('c', 1), ('d', 1)]

The solution in Python code

Option 1:

from collections import Counter
def ordered_count(input):
    c = Counter(input)
    return sorted(list(c.items()), key=lambda x: input.index(x[0]))

Option 2:

def ordered_count(_input):
    l = []
    for i in _input:
        if i not in l:
            l.append(i)
    return [(i, _input.count(i)) for i in l]

Option 3:

Credit Card Issuer Checking in Java

Mon, 13 Sep 2021 01:28:41 +0000

The challenge

Given a credit card number we can determine who the issuer/vendor is with a few basic knowns.

Complete the function getIssuer() that will use the values shown below to determine the card issuer for a given card number. If the number cannot be matched then the function should return the string Unknown.

| Card Type  | Begins With          | Number Length |
|------------|----------------------|---------------|
| AMEX       | 34 or 37             | 15            |
| Discover   | 6011                 | 16            |
| Mastercard | 51, 52, 53, 54 or 55 | 16            |
| VISA       | 4                    | 13 or 16      |

getIssuer(4111111111111111) == "VISA"
getIssuer(4111111111111) == "VISA"
getIssuer(4012888888881881) == "VISA"
getIssuer(378282246310005) == "AMEX"
getIssuer(6011111111111117) == "Discover"
getIssuer(5105105105105100) == "Mastercard"
getIssuer(5105105105105106) == "Mastercard"
getIssuer(9111111111111111) == "Unknown"

The solution in Java code

Option 1:

Find Count of Most Frequent Item in an Array in Java

Sun, 12 Sep 2021 00:58:17 +0000

The challenge

Complete the function to find the count of the most frequent item of an array. You can assume that input is an array of integers. For an empty array return ``

input array: [3, -1, -1, -1, 2, 3, -1, 3, -1, 2, 4, 9, 3]
ouptut: 5

The solution in Java code

Option 1:

import java.util.*;

public class Solution {
  public static int mostFrequentItemCount(int[] collection) {
    if (collection.length==0) return 0;
    Map<Integer, Integer> m = new HashMap<>();
    for (Integer i : collection)
      m.merge(i, 1, Integer::sum);
    return Collections.max(m.values());
  }
}

Option 2:

Return Nth Smallest Element in Java

Sat, 11 Sep 2021 00:05:00 +0000

The challenge

Given an array/list [] of integers, Find the Nth smallest element in this array of integers

Array/list size is at least 3 .
Array/list’s numbers could be a mixture of positives , negatives and zeros .
Repetition in array/list’s numbers could occur, so don’t Remove Duplications .

Examples

nthSmallest({3,1,2} ,2) ==> return (2) 
nthSmallest({15,20,7,10,4,3} ,3) ==> return (7) 
nthSmallest({2,169,13,-5,0,-1} ,4) ==> return (2)

The solution in Java code

Option 1:

What temperature does your Mac CPU idle at?

Fri, 10 Sep 2021 00:26:47 +0000

Sometimes you will find that your Mac is running very hot, and you may want to keep track of it over time to see if it’s persistent or only a spike.

There are tools like Intel’s Power Widget, or even the TurboBoostSwitcher that will show you graphs of these sort of things, but what about getting this information directly from the CLI?

You’re in luck!

sudo powermetrics --samplers smc | grep -i "CPU die temperature"

Split String into Parts in Java

Thu, 09 Sep 2021 00:22:22 +0000

The challenge

Split a given string into different strings of equal size.

Example:

Split the below string into other strings of size #3

'supercalifragilisticexpialidocious'

Will return a new string
'sup erc ali fra gil ist ice xpi ali doc iou s'

Assumptions:

String length is always greater than 0
String has no spaces
Size is always positive

The solution in Java code

Option 1:

public class InParts {
    public static String splitInParts(String s, int partLength) {
        StringBuilder sb = new StringBuilder();
        char[] c = s.toCharArray();
        int k = 0;
      
        for (int i=0; i<c.length; i++) {
          sb.append(c[i]);
          if (k==partLength-1) {
            sb.append(" ");
            k = -1;
          }
          k++;
        }
        
        return sb.toString().trim();
    }
}

Option 2:

[Solved] ERROR 1030 (HY000): Got error 168 from storage engine

Wed, 08 Sep 2021 00:05:07 +0000

If you are getting the following error in MySQL:
ERROR 1030 (HY000): Got error 168 from storage engine

Then this usually means that your server has run out of disk space!

This is never a good thing, but can be resolved by simply deleting some files on the server that you don’t need.

Solution 1: Delete some files

If you have some files on the server that you can delete to free up some space, then do so.

Largest Pair Sum in Array in Python

Tue, 07 Sep 2021 00:05:00 +0000

The challenge

Given a sequence of numbers, find the largest pair sum in the sequence.

For example

[10, 14, 2, 23, 19] -->  42 (= 23 + 19)
[99, 2, 2, 23, 19]  --> 122 (= 99 + 23)

Input sequence contains minimum two elements and every element is an integer.

The solution in Python code

Option 1:

def largest_pair_sum(numbers):
    return sum(sorted(numbers)[-2:])

Option 2:

def largest_pair_sum(numbers):
    max1 = max(numbers)
    numbers.remove(max1)
    max2 = max(numbers)
    return max1 + max2

Option 3:

Alphabet Symmetry in Python

Mon, 06 Sep 2021 00:05:00 +0000

The challenge

Consider the word "abode". We can see that the letter a is in position 1 and b is in position 2. In the alphabet, a and b are also in positions 1 and 2. Notice also that d and e in abode occupy the positions they would occupy in the alphabet, which are positions 4 and 5.

Given an array of words, return an array of the number of letters that occupy their positions in the alphabet for each word. For example,

Exes and Ohs in Java

Sun, 05 Sep 2021 00:05:00 +0000

The challenge

Check to see if a string has the same amount of ‘x’s and ‘o’s. The method must return a boolean and be case insensitive. The string can contain any char.

Examples input/output:

XO("ooxx") => true
XO("xooxx") => false
XO("ooxXm") => true
XO("zpzpzpp") => true // when no 'x' and 'o' is present should return true
XO("zzoo") => false

The solution in Java code

Option 1:

import java.util.*;

public class XO {
  
  public static boolean getXO (String str) {
    
    Map<String, Integer> m = new HashMap<>();
    m.put("x", 0);
    m.put("o", 0);
    
    for (int i = 0; i < str.length(); i++){
      char c = str.charAt(i);        
      
      if (Character.toLowerCase(c)=='x')
        m.put("x", m.get("x")+1);
      
      if (Character.toLowerCase(c)=='o')
        m.put("o", m.get("o")+1);
      
    }
    
    return m.get("x")==m.get("o");
    
  }
}

Option 2:

Sum of Odd Cubed Numbers in Python

Sat, 04 Sep 2021 00:05:00 +0000

The challenge

Find the sum of the odd numbers within an array, after cubing the initial integers. The function should return None if any of the values aren’t numbers.

Note: Booleans should not be considered as numbers.

The solution in Python code

Option 1:

def cube_odd(arr):
    if any(type(x) is not int for x in arr):
        return None
    return sum(x ** 3 for x in arr if x % 2 != 0)

Option 2:

Halving Sum in Python

Fri, 03 Sep 2021 00:32:04 +0000

The challenge

Given a positive integer n, calculate the following sum:

n + n/2 + n/4 + n/8 + ...

All elements of the sum are the results of integer division.

Example

25  =>  25 + 12 + 6 + 3 + 1 = 47

The solution in Python code

Option 1:

def halving_sum(n): 
    total = [n]
    
    while n>=1:
        n = int(n/2)
        total.append(n)
        
    return sum(total)

Option 2:

def halving_sum(n): 
    s=0
    while n: 
        s+=n ; n>>=1
    return s

Option 3:

Convert a LinkedList to a String in Python

Thu, 02 Sep 2021 00:38:30 +0000

The challenge

Preloaded for you is a class, struct, or derived data type Node (depending on the language) used to construct linked lists in this challenge:

class Node():
    def __init__(self, data, next = None):
        self.data = data
        self.next = next

Create a function stringify which accepts an argument list/$list and returns a string representation of the list. The string representation of the list starts with the value of the current Node, specified by its data/$data/Data property, followed by a whitespace character, an arrow, and another whitespace character (" -> "), followed by the rest of the list. The end of the string representation of a list must always end with None. For example, given the following list:

Most Digits from List in Python

Wed, 01 Sep 2021 00:05:00 +0000

The challenge

Find the number with the most digits.

If two numbers in the argument array have the same number of digits, return the first one in the array.

The solution in Python code

Option 1:

def find_longest(xs):
    return max(xs, key=lambda x: len(str(x)))

Option 2:

def find_longest(arr):
    arr.sort(reverse=True) 
    return arr[0]

Option 3:

def find_longest(arr):
    max_lenght = 0
    max_index = 0
    for cur_num in arr:
        lenght = len(str(cur_num))
        if lenght > max_lenght:
            max_lenght = lenght
            max_index = arr.index(cur_num)
    return arr[max_index]

Test cases to validate our solution

import test
from solution import find_longest

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(find_longest([1, 10, 100]), 100)
        test.assert_equals(find_longest([9000, 8, 800]), 9000)
        test.assert_equals(find_longest([8, 900, 500]), 900)
        test.assert_equals(find_longest([3, 40000, 100]), 40000)
        test.assert_equals(find_longest([1, 200, 100000]), 100000)

@test.describe("Random tests")
def random_tests():
    
    from random import randint
    from functools import reduce
    
    sol=lambda arr: reduce(lambda a,b: b if len(str(a))<len(str(b)) else a,arr)
    
    for _ in range(40):
        arr=[randint(1,10**randint(1,20)) for q in range(randint(1,50))]
        expected = sol(arr)
        @test.it(f"Testing for find_longest({arr})")
        def _():
            test.assert_equals(find_longest(arr[:]),expected)

Check if all Values in Array are Smaller in Python

Tue, 31 Aug 2021 00:24:19 +0000

The challenge

You will be given an array and a limit value. You must check that all values in the array are below or equal to the limit value. If they are, return true. Else, return false.

You can assume all values in the array are numbers.

The solution in Python code

Option 1:

def small_enough(array, limit):
    return True if max(array)<=limit else False

Option 2:

def small_enough(array, limit):
    return max(array)<=limit

Option 3:

Maximum Product from List of Integers in Python

Mon, 30 Aug 2021 00:05:00 +0000

The challenge

Given an array of integers, Find the maximum product obtained from multiplying 2 adjacent numbers in the array.

Notes

Array/list size is at least 2.
Array/list numbers could be a mixture of positives, negatives also zeroes .

Input >Output Examples

adjacentElementsProduct([1, 2, 3]); ==> return 6

Explanation:

The maximum product is obtained from multiplying 2 * 3 = 6, and they’re adjacent numbers in the array.

adjacentElementsProduct([9, 5, 10, 2, 24, -1, -48]); ==> return 50

Explanation:

Max product obtained from multiplying 5 * 10 = 50 .

Sum of Array Singles in Python

Sun, 29 Aug 2021 01:42:45 +0000

The challenge

You are given an array of numbers in which two numbers occur once and the rest occur only twice. Your task is to return the sum of the numbers that occur only once.

For example, repeats([4,5,7,5,4,8]) = 15 because only the numbers 7 and 8 occur once, and their sum is 15. Every other number occurs twice.

The solution in Python code

Option 1:

def repeats(arr):
    count = []
    for i in arr:
        if i not in count:
            count.append(i)
        else:
            count.remove(i)
            
    return sum(count)

Option 2:

Flatten and Sort an Array in Python

Sat, 28 Aug 2021 00:05:00 +0000

The challenge

Given a two-dimensional array of integers, return the flattened version of the array with all the integers in the sorted (ascending) order.

Example:

Given [[3, 2, 1], [4, 6, 5], [], [9, 7, 8]], your function should return [1, 2, 3, 4, 5, 6, 7, 8, 9].

The solution in Python code

Option 1:

def flatten_and_sort(array):
    a = []
    for b in array:
        for c in b:
            a.append(c)
    return sorted(a)

Option 2:

Playing the Alphabet War in Python

Fri, 27 Aug 2021 00:05:00 +0000

The challenge

Introduction

There is a war and nobody knows – the alphabet war!
There are two groups of hostile letters. The tension between left side letters and right side letters was too high and the war began.

Task

Write a function that accepts fight string consists of only small letters and return who wins the fight. When the left side wins return Left side wins!, when the right side wins return Right side wins!, in other case return Let's fight again!.

Sum of numbers from 0 to N in Python

Thu, 26 Aug 2021 00:05:00 +0000

The challenge

We want to generate a function that computes the series starting from 0 and ending until the given number.

Example:

Input: > 6

Output: 0+1+2+3+4+5+6 = 21

Input: > -15

Output: -15<0

Input: > 0

Output: 0=0

The solution in Python code

Option 1:

def show_sequence(n):
    if n == 0:
        return "0=0"
    elif n < 0:
        return str(n) + "<0"
    else:
        counter = sum(range(n+1))
        return '+'.join(map(str, range(n+1))) + " = " + str(counter)

Option 2:

Sorted? yes? no? how? ..in Python

Wed, 25 Aug 2021 00:05:00 +0000

The challenge

Complete the method which accepts an array of integers, and returns one of the following:

"yes, ascending" – if the numbers in the array are sorted in an ascending order
"yes, descending" – if the numbers in the array are sorted in a descending order
"no" – otherwise

You can assume the array will always be valid, and there will always be one correct answer.

Complete the method which accepts an array of integers, and returns one of the following:

How to Fix String Casing in Python

Tue, 24 Aug 2021 00:05:00 +0000

The challenge

You will be given a string that may have mixed uppercase and lowercase letters and your task is to convert that string to either lowercase only or uppercase only based on:

make as few changes as possible.
if the string contains equal number of uppercase and lowercase letters, convert the string to lowercase.

For example:

solve("coDe") = "code". Lowercase characters > uppercase. Change only the "D" to lowercase.
solve("CODe") = "CODE". Uppercase characters > lowecase. Change only the "e" to uppercase.
solve("coDE") = "code". Upper == lowercase. Change all to lowercase.

The solution in Python code

Option 1:

How to Remove Duplicate Words from a String in Python

Mon, 23 Aug 2021 00:05:00 +0000

The challenge

Remove all duplicate words from a string, leaving only single (first) words entries.

Example:

Input:

‘alpha beta beta gamma gamma gamma delta alpha beta beta gamma gamma gamma delta'

Output:

‘alpha beta gamma delta'

The solution in Python code

Option 1:

def remove_duplicate_words(s):
    def unique_list(l):
        ulist = []
        [ulist.append(x) for x in l if x not in ulist]
        return ulist

    return ' '.join(unique_list(s.split()))

Option 2:

def remove_duplicate_words(s):
    return ' '.join(dict.fromkeys(s.split()))

Option 3:

How to Validate a Regex PIN Code in Python

Sun, 22 Aug 2021 00:05:00 +0000

The challenge

ATM machines allow 4 or 6 digit PIN codes and PIN codes cannot contain anything but exactly 4 digits or exactly 6 digits.

If the function is passed a valid PIN string, return true, else return false.

Examples

"1234"   -->  true
"12345"  -->  false
"a234"   -->  false

The solution in Python code

Option 1:

def validate_pin(pin):
    return len(pin) in (4, 6) and pin.isdigit()

Option 2:

import re

def validate_pin(pin):
    return bool(re.fullmatch("\d{4}|\d{6}", pin))

Option 3:

Combine strings and remove duplicates in Python

Sat, 21 Aug 2021 00:03:00 +0000

The challenge

Take 2 strings s1 and s2 including only letters from ato z. Return a new sorted string, the longest possible, containing distinct letters – each taken only once – coming from s1 or s2.

Examples:

a = "xyaabbbccccdefww"
b = "xxxxyyyyabklmopq"
longest(a, b) -> "abcdefklmopqwxy"

a = "abcdefghijklmnopqrstuvwxyz"
longest(a, a) -> "abcdefghijklmnopqrstuvwxyz"

The solution in Python code

Option 1 (Using a Dictionary):

def longest(a1, a2):
    a3 = list(dict.fromkeys(sorted(a1+a2)))
    return "".join(a3)

Option 2 (Using a Set):

How to Repeat by String Index in Golang

Fri, 20 Aug 2021 00:05:00 +0000

The challenge

Create a function that repeats each character by the amount of it’s index value of the original string.

Examples:

accum("abcd") -> "A-Bb-Ccc-Dddd"
accum("RqaEzty") -> "R-Qq-Aaa-Eeee-Zzzzz-Tttttt-Yyyyyyy"
accum("cwAt") -> "C-Ww-Aaa-Tttt"

The parameter of accum is a string that includes only letters from a..z and A..Z.

The solution in Golang

Option 1:

package solution

import "strings"

func Accum(s string) string {
    words := make([]string, len(s))
    
    for i, c := range s {
        words[i] = strings.Title(strings.Repeat(strings.ToLower(string(c)), i+1))
    }
   
    return strings.Join(words, "-")
}

Option 2:

How to make an arithmetic function in Java

Thu, 19 Aug 2021 00:04:02 +0000

The challenge

Given two numbers and an arithmetic operator (the name of it, as a string), return the result of the two numbers having that operator used on them.

a and b will both be positive integers, and a will always be the first number in the operation, and b always the second.

The four operators are “add”, “subtract”, “divide”, “multiply”.

A few examples:

arithmetic(5, 2, "add")      => returns 7
arithmetic(5, 2, "subtract") => returns 3
arithmetic(5, 2, "multiply") => returns 10
arithmetic(5, 2, "divide")   => returns 2.5

ArithmeticFunction.arithmetic(5, 2, "add")      => returns 7
ArithmeticFunction.arithmetic(5, 2, "subtract") => returns 3
ArithmeticFunction.arithmetic(5, 2, "multiply") => returns 10
ArithmeticFunction.arithmetic(5, 2, "divide")   => returns 2

The solution in Java code

Option 1:

Calculate the Third Angle of a Triangle in Go

Wed, 18 Aug 2021 00:13:37 +0000

The challenge

You are given two interior angles (in degrees) of a triangle.

Write a function to return the 3rd.

Note: only positive integers will be tested.

The solution in Golang

Option 1:

package solution

func OtherAngle(a int, b int) int {
    return 180-a-b
}

Option 2:

package solution

func OtherAngle(a int, b int) int {
  if a + b > 180{
    return -1
  }
  return 180 - a - b
}

Option 3:

Return Short Long Short in Python

Tue, 17 Aug 2021 00:48:13 +0000

The challenge

Given 2 strings, a and b, return a string of the form short+long+short, with the shorter string on the outside and the longer string on the inside. The strings will not be the same length, but they may be empty ( length `` ).

For example:

solution("1", "22") # returns "1221"
solution("22", "1") # returns "1221"

The solution in Python code

Option 1:

def solution(a, b):
    if a.isdigit():
        if a<b:
            return f"{a}{b}{a}"
        else:
            return f"{b}{a}{b}"
    else:
        if len(a)<len(b):
            return f"{a}{b}{a}"
        else:
            return f"{b}{a}{b}"

Option 2:

Hello, Name or World in Python

Mon, 16 Aug 2021 00:04:28 +0000

The challenge

Define a method hello that returns “Hello, Name!” to a given name, or says Hello, World! if name is not given (or passed as an empty String).

Assuming that name is a String and it checks for user typos to return a name with a first capital letter (Xxxx).

Examples:

hello "john"   => "Hello, John!"
hello "aliCE"  => "Hello, Alice!"
hello          => "Hello, World!" <em># name not given</em>
hello ""       => "Hello, World!" <em># name is an empty String</em>

The solution in Python code

Option 1:

Add Length to Strings in Python

Sun, 15 Aug 2021 00:05:00 +0000

The challenge

What if we need the length of the words separated by a space to be added at the end of that same word and have it returned as an array?

add_length('apple ban') => ["apple 5", "ban 3"]
add_length('you will win') => ["you 3", "will 4", "win 3"]

Your task is to write a function that takes a String and returns an Array/list with the length of each word added to each element.

How to Reversing Words in a String in Python

Sat, 14 Aug 2021 00:05:00 +0000

The challenge

Write a function that reverses the words in a given string. A word can also fit an empty string. If this is not clear enough, here are some examples:

As the input may have trailing spaces, you will also need to ignore unnecessary whitespace.

Example (Input –> Output)

"Hello World" --> "World Hello"
"Hi There." --> "There. Hi"

The solution in Python code

Option 1:

import re

def reverse(st):
    return " ".join(re.sub('\s+', ' ', st).strip().split(" ")[::-1])

Option 2:

How to Remove Duplicates from List in Python

Fri, 13 Aug 2021 00:18:18 +0000

The challenge

Define a function that removes duplicates from an array of numbers and returns it as a result.

The order of the sequence has to stay the same.

The solution in Python code

Option 1:

def distinct(seq):
    return list(dict.fromkeys(seq))

Option 2:

distinct = lambda s: [e for i,e in enumerate(s) if e not in s[:i]]

Option 3:

def distinct(seq):
    result = []
    seen = set()
    for a in seq:
        if a not in seen:
            result.append(a)
            seen.add(a)
    return result

Test cases to validate our solution

import test
from solution import distinct

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(distinct([1]), [1])
        test.assert_equals(distinct([1, 2]), [1, 2])
        test.assert_equals(distinct([1, 1, 2]), [1, 2])
        test.assert_equals(distinct([1, 1, 1, 2, 3, 4, 5]), [1, 2, 3, 4, 5])
        test.assert_equals(distinct([1, 2, 2, 3, 3, 4, 4, 5, 6, 7, 7, 7]), [1, 2, 3, 4, 5, 6, 7])

How to Format Dollars and Cents in Python

Thu, 12 Aug 2021 00:04:19 +0000

The challenge

The company you work for has just been awarded a contract to build a payment gateway. In order to help move things along, you have volunteered to create a function that will take a float and return the amount formatting in dollars and cents.

39.99 becomes $39.99

The rest of your team will make sure that the argument is sanitized before being passed to your function although you will need to account for adding trailing zeros if they are missing (though you won’t have to worry about a dangling period).

Return `5` without any numbers in Python

Wed, 11 Aug 2021 00:17:59 +0000

The challenge

Write a function that always returns 5

Sounds easy right? Just bear in mind that you can’t use any of the following characters: 0123456789*+-/

The solution in Python code

Option 1:

def unusual_five():
    return len(['a','b','c','d','e'])

Option 2:

def unusual_five():
    return len("five!")

Option 3:

def unusual_five():
    return (int(True << True << True ^ True))

Option 4:

def unusual_five():
    return "fiftyfive divided by eleven".count("e")

Test cases to validate our solution

import test
from solution import unusual_five

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Should return 5')
    def basic_test_cases():
        test.assert_equals(unusual_five(),5,"lol")

How to Generate Range of Integers in Python

Tue, 10 Aug 2021 01:13:06 +0000

The challenge

Implement a function named generateRange(min, max, step), which takes three arguments and generates a range of integers from min to max, with the step. The first integer is the minimum value, the second is the maximum of the range and the third is the step. (min < max)

Task

Implement a function named

generate_range(2, 10, 2) # should return list of [2,4,6,8,10]
generate_range(1, 10, 3) # should return list of [1,4,7,10]

generate_range(2, 10, 2) # should return array of [2, 4, 6, 8, 10]
generate_range(1, 10, 3) # should return array of [1, 4, 7, 10]

Note

min < max
step > 0
the range does not HAVE to include max (depending on the step)

The solution in Python code

Option 1:

Blue/Green Deployment Techniques in AWS

Mon, 09 Aug 2021 00:03:52 +0000

What are Blue/Green Deployments?

“Blue/Green Deployments” is a software deployment methodology. A terminology to suggest two mostly equal states of potential different deployable artefacts.

Within the context of Amazon Web Services (AWS), there are a couple of ways to do this.

Let’s explore the two most common ones, then extend that theory to a third one.

Thereafter, we will touch on two more that could be looked at.

1. Route53

Update the DNS routing. With this technique, there is a duplicate stack for both the Blue and the Green environments, and Route53 is utilised to point the DNS to a specific point. It is extremely fast and simple to rollback using this method, by simply changing the DNS records back to what they were before.

How to Calculate Powers of 2 in Python

Sun, 08 Aug 2021 01:04:14 +0000

The challenge

Complete the function that takes a non-negative integer n as input, and returns a list of all the powers of 2 with the exponent ranging from 0 to n (inclusive).

Examples

n = 0  ==> [1]        # [2^0]
n = 1  ==> [1, 2]     # [2^0, 2^1]
n = 2  ==> [1, 2, 4]  # [2^0, 2^1, 2^2]

The solution in Python code

Option 1:

def powers_of_two(n):
    out = []
    for i in range(n+1):
        out.append(2**i)
    return out

Option 2:

How to Get Planet Name By ID in Python

Sat, 07 Aug 2021 00:09:56 +0000

The challenge

Create a function that takes in an id and returns the planet name.

The solution in Python code

Option 1:

def get_planet_name(id):
    return {
        1: "Mercury",
        2: "Venus",
        3: "Earth",
        4: "Mars",
        5: "Jupiter",
        6: "Saturn",
        7: "Uranus" , 
        8: "Neptune"
    }[id]

Option 2:

def get_planet_name(id):
    return ["Mercury","Venus","Earth","Mars","Jupiter","Saturn","Uranus","Neptune"][id-1]

Option 3:

def get_planet_name(id):
    if   id == 1: return "Mercury"
    elif id == 2: return "Venus"
    elif id == 3: return "Earth"
    elif id == 4: return "Mars"
    elif id == 5: return "Jupiter"
    elif id == 6: return "Saturn"
    elif id == 7: return "Uranus"  
    elif id == 8: return "Neptune"

Test cases to validate our solution

import test
from solution import get_planet_name

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(get_planet_name(2), 'Venus')
        test.assert_equals(get_planet_name(5), 'Jupiter')
        test.assert_equals(get_planet_name(3), 'Earth')
        test.assert_equals(get_planet_name(4), 'Mars')
        test.assert_equals(get_planet_name(8), 'Neptune')
        test.assert_equals(get_planet_name(1), 'Mercury')

How to Make a Directory if Not Exists in Python

Fri, 06 Aug 2021 00:05:00 +0000

If you want to create a directory in Python, but only if it doesn’t exist, you have the following option.

Using Python 3.5 or newer?

from pathlib import Path
Path("/your/directory").mkdir(parents=True, exist_ok=True)

Alternative option

import os
if not os.path.exists("/your/directory"):
  os.makedirs("/your/directory")

Square(n) Sum in Python

Thu, 05 Aug 2021 02:17:33 +0000

The challenge

Complete the square sum function so that it squares each number passed into it and then sums the results together.

For example, for [1, 2, 2] it should return 9 because 1^2 + 2^2 + 2^2 = 9.

Complete the square sum function so that it squares each number passed into it and then sums the results together.

For example, for [1, 2, 2] it should return 9 because 1^2 + 2^2 + 2^2 = 9.

How to Fill an Array in Python

Wed, 04 Aug 2021 00:15:47 +0000

The challenge

We want an array, but not just any old array, an array with contents!

Write a function that produces an array with the numbers `` to N-1 in it.

For example, the following code will result in an array containing the numbers `` to 4:

arr(5) # => [0,1,2,3,4]

Note: The parameter is optional. So you have to give it a default value.

The solution in Python code

Option 1:

How to Fix the ‘Bad Interpreter’ Error from AWS and Python 3.7

Tue, 03 Aug 2021 00:05:00 +0000

This error often looks something like:

.zshrc: /usr/local/bin/aws: bad interpreter:
/usr/local/opt/python/bin/python3.6: no such file or directory

Reinstall AWSCLI

If you have started getting the Bad Interpreter error when you call awscli, then you can easily fix it by running:

brew reinstall awscli

Force link the version

Then make sure to link to the correct version:

brew link --overwrite awscli

Retrieve records from MSSQLServer in Python

Mon, 02 Aug 2021 00:05:00 +0000

The below Python code will create a connection to a MSSQLServer instance, and retrieve data from it back into a variable called tblResults.

# use pyodbc for database connection
import pyodbc

# keep our database credentials in a store
secrets = {
    'host': '<db_host>',
    'Name': '<db_name>',
    'username': '<db_username>',
    'password': '<db_password>',
}

# create a connection string
conn_str = f"DRIVER={{ODBC Driver 17 for SQL Server}};SERVER=tcp:{secrets['host']};DATABASE={secrets['Name']};UID={secrets['username']};PWD={secrets['password']}"

# create a connection to the database
conn = pyodbc.connect(conn_str)

# a reusable function to get data from
def sql_get(sql, conn):
    cursor = conn.cursor()
    cursor.execute(sql)
    columns = [column[0] for column in cursor.description]
    results = []
    for row in cursor.fetchall():
        results.append(dict(zip(columns, row)))
    return results

# some variable to use in the SQL statement below
something = 13

# make a database connection and return the results into a variable
tblResults = sql_get(
    f"""SELECT * FROM tblName WHERE something='{something}'"""
, conn)

How to Remove Trailing Zeroes in Python

Sun, 01 Aug 2021 00:05:00 +0000

The challenge

Numbers ending with zeros are boring.

They might be fun in your world, but not here.

Get rid of them. Only the ending ones.

1450 -> 145
960000 -> 96
1050 -> 105
-1050 -> -105

The solution in Python code

Option 1:

def no_boring_zeros(n):
    n = str(n)
    for i in range(len(n)-1, 0, -1):
        if n[i]=="0":
            n = n[:-1:]
        else:
            return int(n)
    return int(n)

Option 2:

def no_boring_zeros(n):
    try:
        return int(str(n).rstrip('0'))
    except ValueError:
        return 0

Option 3:

How to use Profilers in Python

Sat, 31 Jul 2021 00:05:40 +0000

When you have performance problems in your Python application, you can use a Profiler to help you.

Step 1: Using cProfile

Your first option is to run your application with -m cProfile in the cli.

Let’s take an example application that is run as follows:

python app.py

We can run it with a Profiler by doing the following:

python -m cProfile -o outfile app.py

This will give you a report that shows where most of the time is spent while running your app.

If you can’t Sleep, just count Sheep in Python

Fri, 30 Jul 2021 00:05:00 +0000

The challenge

Given a non-negative integer, 3 for example, return a string with a murmur: "1 sheep...2 sheep...3 sheep...". Input will always be valid, i.e. no negative integers.

The solution in Python code

Option 1:

def count_sheep(n):
    sheep = ''
    for i in range(n):
        sheep+=f"{i+1} sheep..."
    return sheep

Option 2:

def count_sheep(n):
    return ''.join(f"{i} sheep..." for i in range(1,n+1))

Option 3:

def count_sheep(n):
    return ('{} sheep...'*n).format(*list(range(1,n+1)))

Test cases to validate our solution

import test
from solution import count_sheep

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(count_sheep(1), "1 sheep...");
        test.assert_equals(count_sheep(2), "1 sheep...2 sheep...")
        test.assert_equals(count_sheep(3), "1 sheep...2 sheep...3 sheep...")

Key-Value CLI Arguments in Python

Thu, 29 Jul 2021 00:05:00 +0000

If you have a CommandLine application (CLI) written in Python, you have a number of ways that you can take arguments from the user.

You could take the order from the user and assign those to variables:

import sys
print( sys.argv )

This will give you a list of all the space separated values.

So if your app is called like:

python app.py var1 var2
# ['app.py', 'var1', 'var2']

As you can see, sys.argv is a list and the arguments start from the second index location.

How to use a Translation Table to Replace Characters in Python

Wed, 28 Jul 2021 00:29:55 +0000

Python provides the ability to create Translation Tables.

our_text = "This is an example of some text"
translation_table = str.maketrans("abefilostz", "4636110572")

print(our_text)
#This is an example of some text

print(our_text.translate(translation_table))
# Th15 15 4n 3x4mp13 06 50m3 73x7

First we create a Translation Table by calling str.maketrans(x, y, z), passing in our characters we want to translate from and to.

Then we apply our translate(table) to a string using our newly created Translation Table.

How to Calculate the Sum of all Numbers in a String in Python

Tue, 27 Jul 2021 00:48:09 +0000

Let’s take the following string:

numbers = "this 1 2 3 4 5 is not a 8 9 10"

How can we sum up all the numbers in this string?

print(sum([int(num) for num in numbers.split(" ") if num.isnumeric()]))
#42

In the above code snippet, we split the string by the space character, then loop through it and ignore anything that is not numeric. Then we sum up the numbers that are remaining.

How to Find all Permutations of a String in Python

Mon, 26 Jul 2021 00:36:30 +0000

Python comes with a very useful module called itertools, which allows us to calculate permutations directly.

from itertools import permutations
perms = [''.join(p) for p in set(permutations('hello'))]
print(perms)
print(len(perms))

This will result in 60 permutations:

#['helol', 'heoll', 'ehlol', 'eholl', 'ollhe', 'lheol', 'lhoel', 'lehol', 'leohl', 'hoell', 'holel', 'eohll', 'eolhl', 'olhel', 'olehl', 'lhelo', 'lhleo', 'lehlo', 'lelho', 'hlelo', 'hlleo', 'elhlo', 'ellho', 'lhloe', 'lhole', 'leloh', 'leolh', 'hlloe', 'hlole', 'elloh', 'elolh', 'lohel', 'loehl', 'oelhl', 'elhol', 'ohlel', 'olleh', 'holle', 'eollh', 'olhle', 'olelh', 'ehllo', 'hello', 'ohlle', 'oellh', 'llheo', 'lleho', 'llhoe', 'lleoh', 'llohe', 'lloeh', 'oehll', 'elohl', 'lohle', 'loelh', 'lolhe', 'loleh', 'hleol', 'hloel', 'ohell']

#60

How to Find all Permutations without Itertools

def permutations(string):
    if len(string) == 1:
        return string

    recursive_perms = []
    for c in string:
        for perm in permutations(string.replace(c,'',1)):
            recursive_perms.append(c+perm)

    return set(recursive_perms)

perms = permutations('hello')
print(perms)
print(len(perms))

This will give us 60 items:

How to Fix ‘no basic auth credentials’ with Docker and AWS ECR

Sun, 25 Jul 2021 00:05:00 +0000

If you are trying to push a Docker image to AWS ECR (Elastic Container Registry) and you get a no basic auth credentials error. Then you can easily fix it as follows!

Replicating the `no basic auth credentials` error

You ran something like this:

docker tag <image> <account>.dkr.ecr.<region>.amazonaws.com/<app>
docker push <image> <account>.dkr.ecr.<region>.amazonaws.com/<app>

You saw something like this:

Using default tag: latest
The push refers to repository [<account>.dkr.ecr.<region>.amazonaws.com/<app>]
2e6d5f7bxxxx: Preparing
d8db3303xxxx: Preparing
32f366d6xxxx: Preparing
no basic auth credentials

How to fix the problem

no basic auth credentials error

How to Reverse Words or Sentences in Python

Sat, 24 Jul 2021 00:15:00 +0000

Let’s take the following sentence:

words = "These are some words"

We can use slices to reverse the order of the string:

print( words[::-1] )
#sdrow emos era esehT

Let’s say we wanted to reverse each word in the sentence, but keep the order of words.

We can once again use slices, but we will compliment it with a list comprehension:

print( " ".join([word[::-1] for word in words.split(" ")]) )
#esehT era emos sdrow

How to Reverse words without using inbuilt modules

Let’s take this a bit further. Let’s say that we were not allowed to use our cool new slice toy, how could we reverse a string?

How to solve AttributeError: ‘int’ object has no attribute ‘split’ – make: [sharedmods] Error 1

Fri, 23 Jul 2021 02:23:06 +0000

If you get the following error while trying to install something via Homebrew

AttributeError: 'int' object has no attribute 'split' - make: *** [sharedmods] Error 1

The solution to this Homebrew issue

First try to solve the actual Homebrew issues:

git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow

This will then allow you to update:

homebrew update

Then:

brew tap aws/tap
brew install aws-sam-cli

Worst case scenario solution

Then you can solve it like this:

sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install
brew doctor
brew update

How the error looks

==> Installing dependencies for aws/tap/aws-sam-cli: python@3.8
==> Installing aws/tap/aws-sam-cli dependency: python@3.8
==> ./configure --prefix=/usr/local/Cellar/python@3.8/3.8.6_2 --enable-ipv6 --datarootdir=/usr/local/Cellar/python@3.8/3.8.6_2/share --datadir=/usr/local/Cellar/python
==> make
Last 15 lines from ~/Library/Logs/Homebrew/python@3.8/02.make:
    self.run_command(cmd_name)
  File "/private/tmp/python@3.8-20210711-18033-10l0nkx/Python-3.8.6/Lib/distutils/cmd.py", line 313, in run_command
    self.distribution.run_command(command)
  File "/private/tmp/python@3.8-20210711-18033-10l0nkx/Python-3.8.6/Lib/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "/private/tmp/python@3.8-20210711-18033-10l0nkx/Python-3.8.6/Lib/distutils/command/build_ext.py", line 340, in run
    self.build_extensions()
  File "./setup.py", line 320, in build_extensions
    self.detect_modules()
  File "./setup.py", line 1695, in detect_modules
    self.detect_readline_curses()
  File "./setup.py", line 930, in detect_readline_curses
    (tuple(int(n) for n in dep_target.split('.')[0:2])
AttributeError: 'int' object has no attribute 'split'
make: *** [sharedmods] Error 1

How to Push a Docker image to AWS ECR

Thu, 22 Jul 2021 01:34:22 +0000

By default, Docker pushes its images to Docker Hub.

While Docker Hub is a great way to share both your public and private images, you may find the rest of your infrastructure on one of the prominent cloud providers.

In this instance, you are using many of the other AWS resources, so why not use Elastic Container Registry – or ECR for short – instead?

In this guide, we will replace <region> with your desired region in AWS. That could look something like eu-west-2 or us-east-1 perhaps.

Complete Guide: How to Base64 Encode a String in Python | Python Base64 Encoding Explained

Wed, 21 Jul 2021 00:53:23 +0000

How to Base64 Encode a String in Python: A Comprehensive Guide

Welcome to our comprehensive guide on how to python base64 encode a string in Python. Whether you’re a beginner or an experienced Python developer, this guide will equip you with the knowledge and techniques to perform efficient and accurate base64 encoding. Let’s dive in and explore the world of Python base64 encoding together!

Understanding Python’s base64 Module

Python’s built-in base64 module provides a convenient way to encode and decode data using the base64 encoding scheme. Before we proceed, let’s ensure we have the base64 module imported:

How to Get 10 Random Numbers in Python

Tue, 20 Jul 2021 00:15:22 +0000

The random module allows you to generate choices.

import random
print(random.choices([i for i in range(1000)], k=10))

This might give us back something like:

[635, 450, 26, 829, 786, 563, 294, 586, 893, 953]

Explaining `random.choice` and `random.choices`

random.choice takes a sequence as a parameter and return a single random item from it.

While random.choices takes a sequence as a parameter and returns a few random items from it. You can specify how many random items to return by populating the k= parameter, as above.

Get the Middle Character in Python

Mon, 19 Jul 2021 00:03:49 +0000

The challenge

Return the middle character of the word. If the word’s length is odd, return the middle character. If the word’s length is even, return the middle 2 characters.

Examples:

getMiddle("test") # should return "es"
getMiddle("testing") # should return "t"
getMiddle("middle") # should return "dd"
getMiddle("A") # should return "A"

Input

A word (string) of length 0 < str < 1000 (In javascript you may get slightly more than 1000 in some test cases due to an error in the test cases). You do not need to test for this. This is only here to tell you that you do not need to worry about your solution timing out.

Convert String to Datetime in Python

Sun, 18 Jul 2021 09:41:37 +0000

If you have a string and want to create a Datetime object out of it in Python, then you can use the Datetime Parse Time method, as follows:

from datetime import datetime
your_datetime = datetime.strptime('May 31 2021  1:23PM', '%Y-%m-%d')

There are 2 very useful functions of datetime, namely:

strptime – Parse a string
strftime – Format a string

A common format you may be looking for is:

%Y-%m-%d %H:%M:%S

How to Abort SQL statements after a set time in MariaDB

Sat, 17 Jul 2021 00:47:47 +0000

Sometimes you don’t want a SELECT query to run for more than a set amount of time.

This is a roundabout way to make your server doesn’t die from slow-running queries.

Obviously, you should tweak your database and potentially run your SELECT queries through an EXPLAIN plan first. This allows you to create appropriate indexes and find why things are slow in the first place.

But: sometimes you still find yourself wanting to kill queries that may run over a certain amount of time.

Multiprocessing Pools in Python

Fri, 16 Jul 2021 01:18:53 +0000

Python ships with a multiprocessing module that allows your code to run functions in parallel by offloading calls to available processors.

In this guide, we will explore the concept of Pools and what a Pool in multiprocessing is.

A Python snippet to play with

Let’s take the following code.

import random, time

def calculate_something(i):
    time.sleep(5)
    print(random.randint(10, 100)*i)

for i in range(5):
   calculate_something(i)

This function will take about 5*5seconds to complete (25seconds?)

How to Double Characters in Python

Thu, 15 Jul 2021 01:08:33 +0000

The challenge

Given a string, you have to return a string in which each character (case-sensitive) is repeated once.

double_char("String") ==> "SSttrriinngg"

double_char("Hello World") ==> "HHeelllloo  WWoorrlldd"

double_char("1234!_ ") ==> "11223344!!__  "

The solution in Python code

This can easily be done by looping through each character and appending it to a list, which we then join and return at the end:

def double_char(s):
    out = []
    for i in s:
        out.append(i+""+i)
    return "".join(out)

However, we could simplify this down to a single list comprehension:

How to Reverse Words in Python

Wed, 14 Jul 2021 00:55:31 +0000

The challenge

Complete the function that accepts a string parameter, and reverses each word in the string. All spaces in the string should be retained.

Examples

"This is an example!" ==> "sihT si na !elpmaxe"
"double  spaces"      ==> "elbuod  secaps"

The solution in Python code

Option 1:

def reverse_words(text):
    out = []
    for word in text.split(" "):
        out.append(word[::-1])
    return " ".join(out)

Option 2:

def reverse_words(str):
    return ' '.join(s[::-1] for s in str.split(' '))

Option 3:

How to Count by X in Python

Tue, 13 Jul 2021 00:45:44 +0000

The challenge

Create a function with two arguments that will return an array of the first (n) multiples of (x).

Assume both the given number and the number of times to count will be positive numbers greater than 0.

Return the results as a list.

Examples

count_by(1,10) #should return [1,2,3,4,5,6,7,8,9,10]
count_by(2,5) #should return [2,4,6,8,10]

The solution in Python code

Option 1:

def count_by(x, n):
    out = []
    for i in range(n):
        out.append(x*(i+1))
    return out

Option 2:

Calculate the Sum of Pairs in Python

Mon, 12 Jul 2021 00:01:55 +0000

The challenge

Given a list of integers and a single sum value, return the first two values (parse from the left please) in order of appearance that add up to form the sum.

sum_pairs([11, 3, 7, 5],         10)
#              ^--^      3 + 7 = 10
== [3, 7]

sum_pairs([4, 3, 2, 3, 4],         6)
#          ^-----^         4 + 2 = 6, indices: 0, 2 *
#             ^-----^      3 + 3 = 6, indices: 1, 3
#                ^-----^   2 + 4 = 6, indices: 2, 4
#  * entire pair is earlier, and therefore is the correct answer
== [4, 2]

sum_pairs([0, 0, -2, 3], 2)
#  there are no pairs of values that can be added to produce 2.
== None/nil/undefined (Based on the language)

sum_pairs([10, 5, 2, 3, 7, 5],         10)
#              ^-----------^   5 + 5 = 10, indices: 1, 5
#                    ^--^      3 + 7 = 10, indices: 3, 4 *
#  * entire pair is earlier, and therefore is the correct answer
== [3, 7]

Negative numbers and duplicate numbers can and will appear.

How to break a list into multiple lists (with maximum size) in Python

Sun, 11 Jul 2021 00:20:20 +0000

If you have a large list and want to create smaller lists of it, with a maximum amount of elements, then:

commands = [str(i) for i in range(100)]
print(len(commands)) #100

chunks = [commands[x:x+5] for x in range(0, len(commands), 5)]

print(len(chunks)) #20
print(chunks)

This will look like:

[
['0', '1', '2', '3', '4'], 
['5', '6', '7', '8', '9'], 
['10', '11', '12', '13', '14'], 
['15', '16', '17', '18', '19'], 
['20', '21', '22', '23', '24'], 
['25', '26', '27', '28', '29'], 
['30', '31', '32', '33', '34'], 
['35', '36', '37', '38', '39'], 
['40', '41', '42', '43', '44'], 
['45', '46', '47', '48', '49'], 
['50', '51', '52', '53', '54'], 
['55', '56', '57', '58', '59'], 
['60', '61', '62', '63', '64'], 
['65', '66', '67', '68', '69'], 
['70', '71', '72', '73', '74'], 
['75', '76', '77', '78', '79'], 
['80', '81', '82', '83', '84'], 
['85', '86', '87', '88', '89'], 
['90', '91', '92', '93', '94'], 
['95', '96', '97', '98', '99']
]

Get all dates between two dates inclusive in Python

Sat, 10 Jul 2021 00:38:04 +0000

If you want to print out a list of all dates between 2 dates (a date range), then you can use the following script:

from datetime import date, timedelta

start_date = date(2021, 5, 31)
end_date = date(2021, 7, 28)

delta = end_date - start_date

for i in range(delta.days + 1):
    day = start_date + timedelta(days=i)
    print(day)

This will result in the following range:

2021-05-31
2021-06-01
...
2021-07-27
2021-07-28

To make sure that you get the format you want back:

How to Append a Python Dictionary to a Pandas DataFrame

Fri, 09 Jul 2021 00:24:39 +0000

If you want to append a Python dictionary to a Pandas DataFrame, you can do this:

# Create a new DataFrame
output = pd.DataFrame()

# Append the dictionary by ignoring the index
output = output.append(dictionary, ignore_index=True)

# View the new DataFrame
print(output.head())

Notice the reassignment output = output.append(...)

Get Secret from AWS Secrets Manager in Python

Thu, 08 Jul 2021 00:57:10 +0000

You can store secrets in AWS Secret Manager and reference their ARN in AWS Systems Secret Manager.

The below snippet allows you to specify the associated parameter to get the secret value.

import boto3

ssm = boto3.client('ssm')
secretsmanager = boto3.client('secretsmanager')

parameter = ssm.get_parameter(Name="/your/parameter/name", WithDecryption=True)
secret = secretsmanager.get_secret_value(SecretId=parameter['Parameter']['Value'])
secret = json.loads(secret['SecretString'])

print(secret)

How to do Binary Addition in Python

Wed, 07 Jul 2021 01:02:35 +0000

The challenge

Implement a function that adds two numbers together and returns their sum in binary. The conversion can be done before or after the addition.

The binary number returned should be a string.

Examples:

add_binary(1, 1) == "10" (1 + 1 = 2 in decimal or 10 in binary)
add_binary(5, 9) == "1110" (5 + 9 = 14 in decimal or 1110 in binary)

The solution in Python code

There are multiple ways to solve an int to binary string problem in Python.

How to Auto-Adjust Excel column widths with pandas.ExcelWriter

Tue, 06 Jul 2021 00:05:07 +0000

You have successfully written your pandas Dataframe to an Excel file, but when you open it, all the columns are squashed up against each other.

There is an easy fix to auto-adjusting your column widths.

Auto Adjusting Column Widths in Pandas

writer = pd.ExcelWriter('file.xlsx') 
df.to_excel(writer, sheet_name='sheetName', index=False, na_rep='NaN')

for column in df:
    column_length = max(df[column].astype(str).map(len).max(), len(column))
    col_idx = df.columns.get_loc(column)
    writer.sheets['sheetName'].set_column(col_idx, col_idx, column_length)

writer.save()

How to Sort the Odd in Python

Mon, 05 Jul 2021 00:28:30 +0000

The challenge

You will be given an array of numbers. You have to sort the odd numbers in ascending order while leaving the even numbers at their original positions.

Examples

[7, 1]  =>  [1, 7]
[5, 8, 6, 3, 4]  =>  [3, 8, 6, 5, 4]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]  =>  [1, 8, 3, 6, 5, 4, 7, 2, 9, 0]

The solution in Python code

Option 1:

Calculate the Sum of the two lowest positive integers in Python

Sun, 04 Jul 2021 01:41:16 +0000

The challenge

Create a function that returns the sum of the two lowest positive numbers given an array of minimum 4 positive integers. No floats or non-positive integers will be passed.

For example, when an array is passed like [19, 5, 42, 2, 77], the output should be 7.

[10, 343445353, 3453445, 3453545353453] should return 3453455.

The solution in Python code

Option 1:

def sum_two_smallest_numbers(numbers):
    return sum(sorted(numbers)[:2])

Option 2:

def sum_two_smallest_numbers(num_list):
    num_list.sort()
    return num_list[0] + num_list[1]

Option 3:

Unique In Order in Python

Sat, 03 Jul 2021 00:42:52 +0000

The challenge

Implement the function unique_in_order which takes as argument a sequence and returns a list of items without any elements with the same value next to each other and preserving the original order of elements.

For example:

unique_in_order('AAAABBBCCDAABBB') == ['A', 'B', 'C', 'D', 'A', 'B']
unique_in_order('ABBCcAD')         == ['A', 'B', 'C', 'c', 'A', 'D']
unique_in_order([1,2,2,3,3])       == [1,2,3]

The solution in Python code

Option 1:

def unique_in_order(iterable):
    result = []
    prev = None
    for char in iterable[0:]:
        if char != prev:
            result.append(char)
            prev = char
    return result

Option 2:

How to Change the Hostname on Linux

Fri, 02 Jul 2021 00:10:36 +0000

On Linux, you can change the hostname by using the hostnamectl command.

How to Set the Hostname on Linux

sudo hostnamectl set-hostname <new-hostname>

For example:

sudo hostnamectl set-hostname server1

At this point, you will need to logout and back in to see the changes have taken effect.

How to Deploy a Docker Container to Kubernetes

Thu, 01 Jul 2021 00:05:23 +0000

Once you have a Docker container, it is really simple to deploy containers to Kubernetes.

Generate a Deployment YAML

kubectl provides a fantastic way to help generate deployment yamls.

kubectl create deployment <app_name> --image=<some/image> --dry-run=client -o yaml > <deployment_file_name>.yaml

Perform the Deployment

Now that we have a deployment yaml, we can simply run:

kubectl apply -f <deployment_file_name>.yaml

What next?

Next you might want to add a Service so that the deployment is available to the world.

How to Replace Characters with Alphabet Positions in Python

Wed, 30 Jun 2021 00:11:48 +0000

The challenge

Given a string, replace every letter with its position in the alphabet.

If anything in the text isn’t a letter, ignore it and don’t return it.

"a" = 1, "b" = 2, etc.

Example

alphabet_position("The sunset sets at twelve o'clock.")

Should return "20 8 5 19 21 14 19 5 20 19 5 20 19 1 20 20 23 5 12 22 5 15 3 12 15 3 11" (as a string)

Returning Highest and Lowest in Python

Tue, 29 Jun 2021 00:03:56 +0000

The challenge

You are given a string of space-separated numbers and have to return the highest and lowest number.

Example:

high_and_low("1 2 3 4 5")  # return "5 1"
high_and_low("1 2 -3 4 5") # return "5 -3"
high_and_low("1 9 3 4 -5") # return "9 -5"

Notes:

All numbers are valid Int32, no need to validate them.
There will always be at least one number in the input string.
Output string must be two numbers separated by a single space, and highest number is first.

The solution in Python code

Option 1:

How to Subtract Arrays in Python

Mon, 28 Jun 2021 00:07:51 +0000

The challenge

Implement a difference function, which subtracts one list from another and returns the result.

It should remove all values from list a, which are present in list b keeping their order.

arrayDiff([1,2],[1]) == [2]

If a value is present in b, all of its occurrences must be removed from the other:

arrayDiff([1,2,2,2,3],[2]) == [1,3]

The solution in Python

Option 1:

def array_diff(a, b):
    return [x for x in a if x not in b]

Option 2:

How to Detect if Numbers are in Order in Golang

Sun, 27 Jun 2021 00:01:55 +0000

The challenge

In this challenge, your function receives an array of integers as input. Your task is to determine whether the numbers are in ascending order. An array is said to be in ascending order if there are no two adjacent integers where the left integer exceeds the right integer in value.

For the purposes of this challenge, you may assume that all inputs are valid, i.e. non-empty arrays containing only integers.

Alternate Capitalization in Golang

Sat, 26 Jun 2021 00:06:33 +0000

The challenge

Given a string, capitalize the letters that occupy even indexes and odd indexes separately, and return as shown below. Index `` will be considered even.

For example, capitalize("abcdef") = ['AbCdEf', 'aBcDeF']. See test cases for more examples.

The input will be a lowercase string with no spaces.

The solution in Golang

Option 1:

package solution

import "unicode"

func Capitalize(s string) []string {
  a, b := []rune(s),[]rune(s)
  for i := range a {
    if i%2 == 0 {
      a[i] = unicode.ToUpper(a[i])
    } else {
      b[i] = unicode.ToUpper(b[i])
    }
  }
  return []string{string(a), string(b)}
}

Option 2:

Check if a String is Uppercase in Golang

Fri, 25 Jun 2021 00:05:07 +0000

The challenge

Create a method IsUpperCase to see whether the string is ALL CAPS. For example:

type MyString string
MyString("c").IsUpperCase() == false
MyString("C").IsUpperCase() == true
MyString("hello I AM DONALD").IsUpperCase() == false
MyString("HELLO I AM DONALD").IsUpperCase() == true
MyString("ACSKLDFJSgSKLDFJSKLDFJ").IsUpperCase() == false
MyString("ACSKLDFJSGSKLDFJSKLDFJ").IsUpperCase() == true

In this challenge, a string is said to be in ALL CAPS whenever it does not contain any lowercase letter so any string containing no letters at all is trivially considered to be in ALL CAPS.

How to UpperCase a String in Golang

Thu, 24 Jun 2021 01:19:20 +0000

In Go, there are multiple ways to make a string UpperCase, each of them are by using the strings package.

Option 1 (`strings.ToUpper`):

func ToUpper(str string) string

package main

import (
    "fmt"
    "strings"
)

func main() {
    str1 := "This is a Test"
    fmt.Println(strings.ToUpper(str1))

    // "THIS IS A TEST"
}

Option 2 (`strings.ToTitle`):

func ToTitle(str string) string

package main

import (
    "fmt"
    "strings"
)

func main() {
    str1 := "This is a Test"
    fmt.Println(strings.ToTitle(str1))

    // "THIS IS A TEST"
}

Return the Shortest Words in Golang

Wed, 23 Jun 2021 00:38:10 +0000

The challenge

Given a string of words, return the length of the shortest word(s).

The input string will never be empty and you do not need to account for different data types.

The solution in Golang

Option 1:

package solution
import "strings"

func FindShort(s string) int {
  shortest := len(s)
  for _, word := range strings.Split(s, " ") {
    if len(word) < shortest {
      shortest = len(word)
    }
  }
  return shortest
}

Option 2:

How to Solve Pascal’s Triangle in Python

Tue, 22 Jun 2021 00:56:16 +0000

The challenge

Given an integer numRows, return the first numRows of Pascal’s triangle.

In Pascal’s triangle, each number is the sum of the two numbers directly above it as shown:

Example 1:

Example 2:

Constraints:

1 <= numRows <= 30

The solution in Python code

class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        triangle = [[1]]
        
        for j in range(1, numRows):
            prev = triangle[-1]
            triangle.append([1] + [prev[i]+prev[i+1] for i in range(len(prev)-1)] + [1])
            
        return triangle

Creating a Multiplication Table for a Number in Golang

Mon, 21 Jun 2021 00:41:35 +0000

The challenge

Your goal is to return multiplication table for number that is always an integer from 1 to 10.

For example, a multiplication table (string) for number == 5 looks like below:

1 * 5 = 5
2 * 5 = 10
3 * 5 = 15
4 * 5 = 20
5 * 5 = 25
6 * 5 = 30
7 * 5 = 35
8 * 5 = 40
9 * 5 = 45
10 * 5 = 50

P. S. You can use \n in string to jump to the next line.

How to Remove Duplicates in an Array in Golang

Sun, 20 Jun 2021 00:04:45 +0000

The challenge

Remove the left-most duplicates from a list of integers and return the result.

// Remove the 3's at indices 0 and 3
// followed by removing a 4 at index 1
solve([3, 4, 4, 3, 6, 3]); // => [4, 6, 3]

The solution in Golang

Option 1:

package solution 

func Solve(arr []int) (res []int) {
    visited := map[int]bool{}
    for i := len(arr) - 1; i >= 0; i-- {
        n := arr[i]
        if visited[n] { continue }
      
        visited[n] = true
        res = append([]int{n}, res...)
    }
  
    return
}

Option 2:

How to Dry Potatoes in Golang

Sat, 19 Jun 2021 00:04:33 +0000

The challenge

All we eat is water and dry matter.

John bought potatoes: their weight is 100 kilograms. Potatoes contain water and dry matter.

The water content is 99 percent of the total weight. He thinks they are too wet and puts them in an oven – at low temperature – for them to lose some water.

At the output the water content is only 98%.

What is the total weight in kilograms (water content plus dry matter) coming out of the oven?

How to Reverse or Rotate in Golang

Fri, 18 Jun 2021 00:18:38 +0000

The challenge

The input is a string str of digits. Cut the string into chunks (a chunk here is a substring of the initial string) of size sz (ignore the last chunk if its size is less than sz).

If a chunk represents an integer such as the sum of the cubes of its digits is divisible by 2, reverse that chunk; otherwise rotate it to the left by one position. Put together these modified chunks and return the result as a string.

How to use Coroutines in Kotlin

Thu, 17 Jun 2021 00:09:13 +0000

Coroutines are a way to handle multithreading in Kotlin, read more about it from the official docs:

https://kotlinlang.org/docs/coroutines-overview.html

An example of a Coroutine in Kotlin

val runBlocking = runBlocking {
  sleep(5)
  delay(1_000L)
  launch {
    delay(1_100L)
    note("inside launch")
  }
  note("outside launch")
}

Introducing the `suspend` keyword

coroutineScopes need to be in wrapping suspend:

suspend fun coroutineFunction(): String {
  return coroutineScope {
    launch {
      println("test")
    }
    "we return this string"
  }
}

runBlocking { println(coroutineFunction()) }

Making Asynchronous API calls using Coroutines

suspend fun call2Apis() {
  val call1 = async {
    delay(1_000L)
    println("got data from api1 @ ${Instant.now()}")
    "some data from api1"
  }
  val call2 = async P
    delay(1_500L)
    println("got data from api2 @ ${Instant.now()}")
    "some data from api2"
  }

  println(call1.await() + " ${Instant.now()}")
  println(call2.await() + " ${Instant.now()}")

}

runBlocking { call2Apis() }
sleep(2)

Simply return a coroutineScope.

The Pair Type in Kotlin

Wed, 16 Jun 2021 00:10:11 +0000

val pair: Pair<String, Int> = "myKey" to 2

What is a Pair Type?

A utility class when you want to return 2 values that are not related to one another.

Some examples

val (a, b) = Pair(1, "x")
println(a) // 1
println(b) // x

Alterantively, you could use:

val p = Pair("x", "y")
println(p) // (x, y)

You can refer to it as first and second

val p = Pair("x", "y")
println(p.first) // x
println(p.second) // y

This is great for returning multiple values from a function.

Get which Quarter of the Year in Golang

Tue, 15 Jun 2021 00:06:59 +0000

The challenge

Given a month as an integer from 1 to 12, return to which quarter of the year it belongs as an integer number.

For example: month 2 (February), is part of the first quarter; month 6 (June), is part of the second quarter; and month 11 (November), is part of the fourth quarter.

The solution in Golang

Option 1:

package solution

func QuarterOf(month int) int {
  return (month + 2) / 3
}

Option 2:

How to Sum The Strings in Python

Mon, 14 Jun 2021 10:46:58 +0000

The challenge

Create a function that takes 2 nonnegative integers in form of a string as an input, and outputs the sum (also as a string):

Example: (Input1, Input2 –>Output)

"4",  "5" --> "9"
"34", "5" --> "39"

Notes:

If either input is an empty string, consider it as zero.
Inputs and the expected output will never exceed the signed 32-bit integer limit (2^31 - 1)

The solution in Python code

Option 1:

Fixing: ImmutableService requires getRowNodeId() callback to be implemented, your row data need IDs

Sun, 13 Jun 2021 00:33:00 +0000

If you have gotten this error before, then you have been trying to implement a rowData mapping onto Ag-Grid.. and failed!

ImmutableService requires getRowNodeId() callback to be implemented, your row data need IDs

How to fix the ‘Your row data need IDs’ error

The good thing, is that it’s actually quite an easy fix:

Make sure that you have implemented the getRowNodeId function to return an actual id:

this.getRowNodeId = function(data) {
  return data.id; //id is a field here
};

Worst case scenario, you could always return a random number here, but that is not recommended; but it certainly does help if you’re in a sticky situation:

How to Undo the most recent local commits in Git

Sat, 12 Jun 2021 01:20:45 +0000

If you have accidentally committed the wrong files into Git, but haven’t yet pushed it to the server, you can recover, or undo your commit as follows:

How to Undo a Commit and Redo it

You have just committed a file, and find yourself here;

We will call this “your accident location”.

Step 1

git commit -m "This is what you've just done"

Step 2

Start by resetting:

git reset HEAD~

Step 3

Now you can edit your files as required.

Deconstruction in Kotlin

Fri, 11 Jun 2021 00:07:47 +0000

There are times when you need to extract an object into a number of variables.

Let’s take the example below:

val (id, name, position, department) = employee

In Kotlin, this is known as a destructuring declaration. These new variables can now be used independently.

The compilation thereof would look something like this, but is not required:

val id = employee.component1()
val name = employee.component2()
val position = employee.component3()
val department = employee.component4()

Returning multiple values from a Function

Much like deconstruction of variables and collections, functions too can return multiple values.

Playing with passphrases in Python

Thu, 10 Jun 2021 01:01:04 +0000

The challenge

Everyone knows passphrases. One can choose passphrases from poems, songs, movies names and so on but frequently they can be guessed due to common cultural references. You can get your passphrases stronger by different means. One is the following:

choose a text in capital letters including or not digits and non alphabetic characters,

shift each letter by a given number but the transformed letter must be a letter (circular shift),
replace each digit by its complement to 9,
keep such as non alphabetic and non digit characters,
downcase each letter in odd position, upcase each letter in even position (the first character is in position 0),
reverse the whole result.

Example:

your text: “BORN IN 2015!”, shift 1

What is a Unit in Kotlin?

Wed, 09 Jun 2021 00:57:51 +0000

Unit corresponds to the void keyword in Java.

What is a `Unit` in Kotlin?

If you have a function that does not return a value, you can return a Unit object.

Generally, you would return a Unit in Kotlin where you would traditionally return a void in Java.

fun doesntReturnAnythign(): Unit {
    val one = 1
}

How to declare a Function in Kotlin?

Tue, 08 Jun 2021 00:30:31 +0000

Functions are reusable pieces of code, often called Blocks, that as the name suggests, act as building blocks to piece together a program.

Each language has its own keyword for defining a function block.

What is `fun`?

The fun keyword in Kotlin denotes a function, or method to wrap a reusable code block.

fun prepends the name of a function as illustrated below.

fun functionName(): String {
    return "A String"
}

The structure of a Kotlin function

The function can take any number of parameters, and a return type.

The differences between Val and Var in Kotlin

Mon, 07 Jun 2021 00:21:27 +0000

Among all the many keywords that Kotlin comes with, there exists val and var. What are they used for? What are the differences, and why would you use one over another?

They are both used to declare variables in Kotlin. But how are they different?

What is `val`?

val is used to declare a variable that is read-only, and who’s value does not change.

Note that this only applies to the parent variable, and not it’s properties. The properties of the variable are still mutable.

Automatically Resize All Columns to Fit in Ag-Grid

Sun, 06 Jun 2021 02:50:51 +0000

If you have an Ag-Grid, and want to automatically resize all the columns to fit the width of the viewport, you can use this hack.

The implementation

/**
   * resizes the columns to fit the width of the grid
   * @param allowShrink if false, columns will NOT be resized when there is no "empty" horizontal space
   * https://stackoverflow.com/questions/55587083/ag-grid-sizecolumnstofit-only-when-there-is-space-available-in-the-total-grid-wi#answer-60753786
   */
  public resizeColumnsToFit(allowShrink = true) {
    if (this.gridApi) {
      if (allowShrink) {
        this.gridApi.sizeColumnsToFit();
      } else {
        /**
         * this is a "hacK" - there is no way to check if there is "empty" space in the grid using the
         * public grid api - we have to use the internal tools here.
         * it could be that some of this apis will change in future releases
         */
        const panel = this.gridApi["gridPanel"];
        const availableWidth = this.gridApi["gridPanel"].eBodyViewport.clientWidth;
        const columns = this.gridApi["gridPanel"]["columnController"].getAllDisplayedColumns();
        const usedWidth = this.gridApi["gridPanel"]["columnController"].getWidthOfColsInList(columns);

        if (usedWidth < availableWidth)
          this.gridApi.sizeColumnsToFit()
      }
    }
  }

How to use this code

Make sure that the following is in your HTML, to trigger the onRowDataChanged event:

How to Get All Rows in Ag-Grid

Sat, 05 Jun 2021 01:36:27 +0000

The easiest way to get the content of all rows’ data, back into a Javascript/Typescript array, is as follows.

Simply create a blank array, then loop through the rows of the grid and append each row to the array.

getAllRows() {
  let rowData = [];
  this.gridApi.forEachNode(node => rowData.push(node.data));
  return rowData;
}

Find the Max Area of an Island in Python

Fri, 04 Jun 2021 00:21:47 +0000

The challenge

You are given an m x n binary matrix grid. An island is a group of 1‘s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

The area of an island is the number of cells with a value 1 in the island.

Return the maximum area of an island in grid. If there is no island, return ``.

Using Apache POI to Get or Create a Sheet in Excel using Java

Thu, 03 Jun 2021 00:05:51 +0000

Apache POI provides a mechanism to work with Excel documents.

However, it has a missing feature when you want to only create a new sheet if one with that name doesn’t already exist.

Luckily, it’s quite simple to get around this using the following code.

List<String> sheets = new ArrayList<>();
for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
    Sheet sheet = workbook.getSheetAt(i);
    sheets.add(sheet.getSheetName());
}
Sheet sheet = sheets.contains(name) ?
                workbook.getSheet(name) :
                workbook.createSheet(name);

The code uses the workbook object you pass it, checks to see if a sheet with the specified name exists and then only creates one if needed. Otherwise it returns a reference to the existing one.

A Simplistic TCP Finite State Machine (FSM) in Python

Wed, 02 Jun 2021 00:02:27 +0000

The challenge

Automatons, or Finite State Machines (FSM), are extremely useful to programmers when it comes to software design. You will be given a simplistic version of an FSM to code for a basic TCP session.

The outcome of this exercise will be to return the correct state of the TCP FSM based on the array of events given.

The input array of events will consist of one or more of the following strings:

How to Resolve Scaling Squared Strings in Java

Tue, 01 Jun 2021 07:23:25 +0000

The challenge

You are given a string of n lines, each substring being n characters long. For example:

s = "abcd\nefgh\nijkl\nmnop"

We will study the “horizontal” and the “vertical” scaling of this square of strings.

A k-horizontal scaling of a string consists of replicating k times each character of the string (except ‘\n’).

Example: 2-horizontal scaling of s: => “aabbccdd\neeffgghh\niijjkkll\nmmnnoopp”

A v-vertical scaling of a string consists of replicating v times each part of the squared string.

How to Build a Square in Python

Mon, 31 May 2021 00:16:10 +0000

The challenge

I will give you an integer. Give me back a shape that is as long and wide as the integer. The integer will be a whole number between 1 and 50.

Example

n = 3, so I expect a 3×3 square back just like below as a string:

+++
+++
+++

The solution in Python

Option 1:

def generateShape(i):
    return (i-1)*(('+'*i)+'\n')+('+'*i)

Option 2:

def generateShape(integer):
    return '\n'.join('+' * integer for i in range(integer))

Option 3:

Check if String EndsWith in Python

Sun, 30 May 2021 01:54:52 +0000

The challenge

Complete the solution so that it returns true if the first argument(string) passed in ends with the 2nd argument (also a string).

Examples:

strEndsWith('abc', 'bc') # returns true
strEndsWith('abc', 'd') # returns false

The solution in Python

def solution(string, ending):
    return string.endswith(ending)

Test cases to validate our solution

test.assert_equals(solution('abcde', 'cde'), True)
test.assert_equals(solution('abcde', 'abc'), False)
test.assert_equals(solution('abcde', ''), True)

How to add a Git Submodule to an existing codebase

Sat, 29 May 2021 00:24:32 +0000

Git submodules are a way of including another repository’s code into an existing codebase, without associating it’s code or tracking history in the parent repository.

Add a Git Submodule to an Existing Codebase

cd <parent_codebase_root>
git submodule add <remote_url> <destination_folder>

So let’s say that we have a project called project_website, a repository at the following path https://github.com/user/repo.git and a target folder we’d like the submodule added to at user_repo, we could construct our query like this:

How to LowerCase a String in Python

Fri, 28 May 2021 00:10:50 +0000

Python comes with a built-in method on all String types, by calling lower() on a String, you can immediately lower the case of that String.

An example to LowerCase a String in Python

words = "These are some WORDS"
words.lower() # <- How to lowerCase a String
# output: these are some words

"These are some WORDS".lower() # <- How to lowerCase a String
# output: these are some words

Now let’s try and see how it may look in a coding challenge:

How to Restart Sound Driver on a Mac

Thu, 27 May 2021 00:14:17 +0000

So for some strange reason, your audio has stopped playing through the Macbook Pro speakers, but if you plug in an external audio device, it still works? Or perhaps some other undesirable combination?

If so, you could just try restarting the computer. That usually fixes thing right?

But you have all those million apps open, all in unsaved states.. So rebooting is not the preferred approach.

Try the below option to give your Apple the kick it needs!

Number to Binary Conversion in Python

Wed, 26 May 2021 01:04:28 +0000

If you have a decimal number, and want to get it’s binary value, you can use the built-in bin method.

decimal = 32
binary = bin(decimal)

# '0b100000'

We can see that it prepends the string with a 0b.

Let’s remove this to return a usable binary value:

decimal = 32
binary = str(bin(decimal)[2:])

# '100000'

Counting Binary Gaps with Python

Tue, 25 May 2021 08:10:34 +0000

The challenge

A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N.

For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of length 3. The number 20 has binary representation 10100 and contains one binary gap of length 1. The number 15 has binary representation 1111 and has no binary gaps. The number 32 has binary representation 100000 and has no binary gaps.

How to Delete a Secret in Kubernetes

Mon, 24 May 2021 00:25:09 +0000

Once you have a secret in Kubernetes, if you know it’s name, you can delete it.

How to find the secret name

You can get the secret name as follows:

kubectl get secrets

This will produce an output similar to:

NAME                  TYPE                                  DATA      AGE
admin-user-pass       Opaque                                2         11s

Now that we have the secret name, we can delete the secret

Deleting a Secret in Kubernetes

kubectl delete secret admin-user-pass

How to Decode a Secret in Kubernetes

Sun, 23 May 2021 00:36:10 +0000

Secrets in Kubernetes are encoded using base64.

If you have the secret name, you can ask for its value. If not, then learn how to get a secret in Kubernetes.

How to retrieve the value of a secret in Kubernetes

kubectl get secret admin-user-pass -o jsonpath='{.data}'

This will output a JSON as follows:

{"password":"amYzOTJoZjc4MmhmOTMyaAo=","username":"YWRtaW51c2VyCg=="}

How to decode the value of a secret in Kubernetes

Values are always base64 encoded, so decoding it will look like this:

How to Verify a Secret in Kubernetes

Sat, 22 May 2021 00:04:57 +0000

You have created a secret, and would like to retrieve it.

Get a list of all the secrets in Kubernetes

kubectl get secrets

This will result in:

NAME                  TYPE                                  DATA      AGE
admin-user-pass       Opaque                                2         11s

How to view a secret in Kubernetes

Now that we have our secret’s name, we can view it directly

kubectl describe secrets/admin-user-pass

With the following output:

Name:            admin-user-pass
Namespace:       default
Labels:          <none>
Annotations:     <none>

Type:            Opaque

Data
====
password:    12 bytes
username:    5 bytes

How to Create a Secret in Kubernetes

Fri, 21 May 2021 01:25:47 +0000

Secrets allow applications to not hardcode usernames, passwords or additional information such as hostnames, IP addresses or other protected/sensitive information.

Create a Secret in Kubernetes

It’s simple to create a secret in Kubernetes. It can either be done --from-file or --from-literal.

Option 1: From a File

echo -n 'adminuser' > ./username.txt
echo -n 'jf392hf782hf932h' > ./password.txt

kubectl create secret generic admin-user-pass \
  --from-file=./username.txt \
  --from-file=./password.txt

The result will be something like:

secret/admin-user-pass created

By default, the key name is the filename, but we could also be explicit about this:

How to Divide an Array into Chunks in PHP

Thu, 20 May 2021 00:43:23 +0000

If you have a single-dimensional array, and want to break it into chunks, you can use the array_chunks method.

It takes 3 arguments:

The input array / original array
The length of the new array (how many dimensions to create)
A boolean to preserve the original keys or not

array_chunk(array $array, int $length, bool $preserve_keys=false ):array

An example of dividing an array into chunks

Let’s take an initial starter array with 5 values

$input_array = array('a', 'b', 'c', 'd', 'e');

If we said we would like to create 2 chunks:

How to setup Certbot wildcard certificate on Apache

Wed, 19 May 2021 01:10:46 +0000

Certbot allows simple, quick and free provisioning of SSL certificates using LetsEncrypt.

How to install Certbot

Option 1 (recommended)

sudo snap install core; sudo snap refresh core
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot

Option 2

apt update
apt install certbot

How to run Certbot

If you want to run the automated setup and get your certificate installed directly to apache, then:

sudo certbot --apache

If you only want the certificate, then:

How to retrieve a Secret from AWS Secrets Manager in the CLI

Tue, 18 May 2021 00:13:56 +0000

If you have stored a secret in AWS using the Secrets Manager, it is possible to use the AWS CLI to retrieve this value at a later date.

aws secretsmanager get-secret-value --secret-id <ARN>

The arn is the Amazon Resource Name, which will look something like this:

aws secretsmanager get-secret-value --secret-id arn:aws:secretsmanager:<region>:<account>:<secretname>

Get a Secret from AWS Secrets Manager using the CLI

aws secretsmanager get-secret-value --secret-id arn:aws:secretsmanager:eu-west-1:4872719xxxxx:secret:NameOfOurSecret-xxx

Determine the Last Digits of N^2 == N in Java

Mon, 17 May 2021 09:33:13 +0000

The challenge

Let’s call an integer number N ‘green’ if N² ends with all of the digits of N. Some examples:

5 is green, because 5² = 25 and 25 ends with 5.

11 is not green, because 11² = 121 and 121 does not end with 11.

376 is green, because 376² = 141376 and 141376 ends with 376.

Your task is to write a function green that returns nth green number, starting with 1 – green (1) == 1

How to Expose your App through a Service in Kubernetes

Sun, 16 May 2021 01:08:11 +0000

Once you have deployed an application into Kubernetes, it will not be available to the outside world.

For this to be possible, you need to expose it via a Service.

Services can be exposed in 4 different ways:

ClusterIP (default) – Exposes the Service via an internal IP to the cluster (only available internally)
NodePort – Exposes the Service via the same port on all Nodes
LoadBalancer – Creates an external LoadBalancer in the current cloud
ExternalName – Maps the Service to the externalName, and returns a CNAME record with it’s value

How to Expose your App via a Service in Kubernetes

kubectl get pods to list your available pods.

How to connect to Bash on a Kubernetes pod

Sat, 15 May 2021 01:27:39 +0000

If you find yourself needing to jump into a Kubernetes pod to either diagnose an issue, or run a particular command, you can use the bash connectivity functionality available from kubectl itself.

1. Get the pod name to connect to

First, you will need the pod name you want to connect to, you can get this by running kubectl get pods

This will return a list similar to:

$ kubectl get pods
NAME                                  READY   STATUS    RESTARTS   AGE
kubernetes-bootcamp-fb5c67579-8tghg   1/1     Running   0          7m39s

Take node of the name cell for later use.

How to get the Environment variables in a Kubernetes Pod

Fri, 14 May 2021 02:01:13 +0000

In this comprehensive guide, you will learn how to effectively get and list environment variables within a Kubernetes pod. Understanding how to work with environment variables is essential for managing and configuring applications running in Kubernetes clusters. We will cover step-by-step instructions to retrieve the environment variables of a pod, along with in-depth explanations and practical examples for a deeper understanding. By the end of this post, you will be proficient in using kubectl commands to handle environment variables in your Kubernetes environment.

How to find out Cluster Info in Kubernetes

Thu, 13 May 2021 00:27:41 +0000

In Kubernetes, a cluster is a group of machines working together.

By running the kubectl cluster-info command, we can find out high level information about the Kubernetes cluster, such as:

What address the cluster is running from
Where the CoreDNS is running from

Example use of KubeCtl Cluser Info

kubectl cluster-info will return the following:

$ kubectl cluster-info

Kubernetes master is running at https://998a8a4d-354e-4203-bafb-2e25d7b39269.k8s.example.com
CoreDNS is running at https://998a8a4d-354e-4203-bafb-2e25d7b39269.k8s.example.com/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

How to get more information about the cluster

You can also append the keyword dump to the above command to get a full output about the cluster.

How to set and use a kubeconfig in Kubernetes

Wed, 12 May 2021 04:31:12 +0000

The kubeconfig file is the main configuration file that allows access to a Kubernetes cluster.

When you first create your Kubernetes cluster, you are given a generated yaml file.

How to configure the kubeconfig file

The kubectl CLI has the followings preference in which kubeconfig file to use:

by adding the --kubeconfig <file>
by setting a KUBECONFIG environment variable
by using the $HOME/.kube/config file on the local machine

How to Map over a List of Lists in Java

Tue, 11 May 2021 00:25:01 +0000

The challenge

Write a function which maps a function over the lists in a list:

public static <T,R> R[][] gridMap(Function<T,R> fn, T[][] list)

Example 1:

int[][] x = {{1,2,3},
             {4,5,6}};

gridMap(e -> e + 1, x); // {{2,3,4},{5,6,7}}
gridMap(e -> e * e, x); // {{1,4,9},{16,25,36}}

Example 2:

char[][] x = {{'h','E','l','l','O'},{'w','O','r','L','d'}};

gridMap(e -> Character.toUpperCase(e), x); // {{'H','E','L','L','O'},{'W','O','R','L','D'}}

The solution in Java code

Option 1:

import java.util.function.Function;
import java.util.Arrays;

public class Solution {
  public static <T, R> Object[][] gridMap(Function<T, R> fn, T[][] list) {
    return Arrays.stream(list).map(xs -> Arrays.stream(xs).map(fn).toArray()).toArray(Object[][]::new);
  }
}

Option 2:

How to Differentiate a Polynomial in Java

Mon, 10 May 2021 00:03:32 +0000

The challenge

Create a function that differentiates a polynomial for a given value of x.

Your function will receive 2 arguments: a polynomial as a string, and a point to evaluate the equation as an integer.

Assumptions:

There will be a coefficient near each x, unless the coefficient equals 1 or -1.
There will be an exponent near each x, unless the exponent equals `` or 1.
All exponents will be greater or equal to zero

Examples:

Equation.differenatiate("12x+2", 3)      ==>   12
Equation.differenatiate("x^2+3x+2", 3)   ==>   9

The solution in Java code

Option 1:

Find the Sums of Perfect Squares in Java

Sun, 09 May 2021 03:04:46 +0000

The challenge

The task is simply stated. Given an integer n (3 < n < 109), find the length of the smallest list of perfect squares which add up to n. Come up with the best algorithm you can; you’ll need it!

Examples:

sum_of_squares(17) = 2
17 = 16 + 1 (4 and 1 are perfect squares).
sum_of_squares(15) = 4
15 = 9 + 4 + 1 + 1. There is no way to represent 15 as the sum of three perfect squares.
sum_of_squares(16) = 1
16 itself is a perfect square.

Time constraints:

[Solved] Error: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.4.4:repackage (repackage)

Sat, 08 May 2021 01:18:02 +0000

If you have come across this error when trying to build and deploy your Spring Boot Maven application then this post will help you!

Error: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.4.4:repackage (repackage)

How to fix the Repackage Execute Goal Error

You need to make sure you have the mainClass explicitly defined under your build->plugin as follows:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <mainClass>com.example.apps.YourApplication</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

[Solved] No main manifest attribute Solution for Jar/Maven/Gradle/Spring Boot

Fri, 07 May 2021 01:43:06 +0000

You’ve built a Java project and packaged a .jar file.

You are ready to run it outside your IDE, or deploy it somewhere.

When you run it using java -jar <your.jar> it says something like this:

no main manifest attribute, in /src/project/target/your-jar-1.0-SNAPSHOT.jar

How to add a Manifest file

You need to create a META-INF/MANIFEST.MF file with the following content:

Main-Class: com.mypackage.MyClass

The class name com.mypackage.MyClass is the main class that has the public static void main(String[] args) entry point in your application.

[Solved] Error – The following untracked working tree files would be overwritten by merge

Thu, 06 May 2021 00:20:05 +0000

So you just tried to do a git pull and got the following error:

error: The following untracked working tree files would be overwritten by merge:

How to fix Untracked Working Trees Overwritten Merge

You can fix this error by first adding and stashing your local files before performing the pull.

git add * 
git stash
git pull

How to Strip Script Tags in PHP

Wed, 05 May 2021 00:17:01 +0000

If you have some HTML input submitted from a user to your application, before saving it to the database, you may want to strip all <script> tags so that you can prevent cross site scripting attacks and other potential issues.

Below we use a Regular Expression to strip the script tag out of a variable.

$html = preg_replace('#<script(.*?)>(.*?)</script>#is', '', $html);

How to Make a Spiral in Java

Tue, 04 May 2021 00:55:45 +0000

The challenge

Your task, is to create a NxN spiral with a given size.

For example, spiral with size 5 should look like this:

and with the size 10:

Return value should contain array of arrays, of `` and 1, for example for given size 5 result should be:

[[1,1,1,1,1],[0,0,0,0,1],[1,1,1,0,1],[1,0,0,0,1],[1,1,1,1,1]]

Because of the edge-cases for tiny spirals, the size will be at least 5.

Find the Longest Common Subsequence in Java

Mon, 03 May 2021 01:14:22 +0000

The challenge

from Wikipedia:
The longest common subsequence (LCS) problem is the problem of finding the longest subsequence common to all sequences in a set of sequences.
It differs from problems of finding common substrings: unlike substrings, subsequences are not required to occupy consecutive positions within the original sequences.

Task

Write a function lcs that accepts two strings and returns their longest common subsequence as a string. Performance matters.

Find First and Last Position of Element in Sorted Array in Java

Sun, 02 May 2021 00:28:30 +0000

The challenge

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

If target is not found in the array, return [-1, -1].

Follow up: Could you write an algorithm with O(log n) runtime complexity?

Example 1:

Example 2:

Example 3:

Determine if Number is a Power of Three in Java

Sat, 01 May 2021 02:58:53 +0000

The challenge

Given an integer n, return true if it is a power of three. Otherwise, return false.

An integer n is a power of three, if there exists an integer x such that n == 3x.

Example 1:

Example 2:

Example 3:

Example 4:

How to Count Binary Substrings in Java

Fri, 30 Apr 2021 00:52:38 +0000

The challenge

Give a string s, count the number of non-empty (contiguous) substrings that have the same number of 0’s and 1’s, and all the 0’s and all the 1’s in these substrings are grouped consecutively.

Substrings that occur multiple times are counted the number of times they occur.

Example 1:

Example 2:

Note:s.length will be between 1 and 50,000.s will only consist of “0” or “1” characters.

How to Download a CSV file using Javascript

Thu, 29 Apr 2021 02:34:45 +0000

Ever wanted to generate a CSV (comma separated values) file directly from the browser, using Javascript? Instead of going to the server..

Look no further!

Create a function to download a csv file

function downloadCsv(csvData: string, filename: string) {
      const blob = new Blob(['\ufeff' + csvData], {
        type: 'text/csv;charset=utf-8;'
      });
      const dwldLink = document.createElement("a");
      const url = URL.createObjectURL(blob);
      const isSafariBrowser = navigator.userAgent.indexOf('Safari') !== -1 && navigator.userAgent.indexOf('Chrome') === -1;

      //if Safari open in new window to save file with random filename.
      if (isSafariBrowser)
        dwldLink.setAttribute("target", "_blank");
      
      dwldLink.setAttribute("href", url);
      dwldLink.setAttribute("download", filename+ ".csv");
      dwldLink.style.visibility = "hidden";
      document.body.appendChild(dwldLink);
      dwldLink.click();
      document.body.removeChild(dwldLink);
}

How to use our function

// define some data
const data = 'Col1,Col2,Col3,Col4,Col5,Col6,Col7,Col8\n' +
             '12345,abc.de,AB1234567890,USD,01-Jan-21,100,10000000,1.23\n' +
             '12345,abc.de,AB1234567890,USD,01-Jan-21,100,10000000,\n' +
             '12345,abc.de,AB1234567890,USD,01-Jan-21,100,';

// define a file name
const file = 'OurFile';

// use the function
downloadCsv(data, file);

Array Range between Integers in Java

Wed, 28 Apr 2021 00:16:52 +0000

The challenge

Complete the function that takes two integers (a, b, where a < b) and return an array of all integers between the input parameters, including them.

For example:

a = 1
b = 4

//[1, 2, 3, 4]

The solution in Java code

Option 1:

public class Solution {

  public static int[] between(int a, int b) {
    return java.util.stream.IntStream.rangeClosed(a, b).toArray();
  }

}

Option 2:

public class Solution {

  public static int[] between(int a, int b) {
    int length = 0;
        for(int k = a; k <= b; k++){
            length++;
        }

        int[] array = new int[length];
        int first = a;

        for(int i = 0; i < length; i++){
            array[i] = first;
            first++;

        }
        return array;
  }

}

Option 3:

How to clone a table structure in MySQL

Tue, 27 Apr 2021 00:03:04 +0000

I have often needed to clone a table without it’s data in MySQL.

Oftentimes this has been because I have a continually growing temporary table and I just need to clear up some disk space. And it’s a lot faster and more guaranteed than trying to delete and optimise the table.

Clone a table structure without it’s data

Let’s say that your table in question is called table1:

create table table1tmp like table1;
drop table table1;
rename table table1tmp to table1;

If you run the above queries either in quick succession, or altogether in a single statement, you will notice that this is a very fast method even on very big tables.

Number of Rectangles in a Grid in Java

Mon, 26 Apr 2021 01:19:01 +0000

The challenge

Given a grid of size m x n, calculate the total number of rectangles contained in this rectangle. All integer sizes and positions are counted.

Examples:

numberOfRectangles(3, 2) == 18
numberOfRectangles(4, 4) == 100

Here is how the 3×2 grid works (Thanks to GiacomoSorbi for the idea):

1 rectangle of size 3×2:

[][][]
[][][]

2 rectangles of size 3×1:

[][][]

4 rectangles of size 2×1:

[][]

2 rectangles of size 2×2

[][]
[][]

3 rectangles of size 1×2:

Longest vowel chain in Java

Sun, 25 Apr 2021 00:53:34 +0000

The challenge

The vowel substrings in the word codewarriors are o,e,a,io. The longest of these has a length of 2. Given a lowercase string that has alphabetic characters only (both vowels and consonants) and no spaces, return the length of the longest vowel substring. Vowels are any of aeiou.

The solution in Java code

Option 1:

import static java.util.stream.Stream.of;

interface Solution {
  static int solve(String s) {
    return of(s.split("[^aeiou]")).mapToInt(String::length).max().orElse(0);
  }
}

Option 2:

Determine Unique String Characters in Java

Sat, 24 Apr 2021 00:46:32 +0000

The challenge

In this challenge, you will be given two strings a and b and your task will be to return the characters that are not common in the two strings.

For example:

solve("xyab","xzca") = "ybzc" 
--The first string has 'yb' which is not in the second string. 
--The second string has 'zc' which is not in the first string.

Notice also that you return the characters from the first string concatenated with those from the second string.

Difference of Volumes of Cuboids in Java

Fri, 23 Apr 2021 00:37:47 +0000

The challenge

In this simple exercise, you will create a program that will take two lists of integers, a and b. Each list will consist of 3 positive integers above 0, representing the dimensions of cuboids a and b. You must find the difference of the cuboids’ volumes regardless of which is bigger.

For example, if the parameters passed are ([2, 2, 3], [5, 4, 1]), the volume of a is 12 and the volume of b is 20. Therefore, the function should return 8.

Sort by binary ones in Java

Thu, 22 Apr 2021 00:18:24 +0000

The challenge

In this example you need to implement a function that sort a list of integers based on it’s binary representation.

The rules are simple:

sort the list based on the amount of 1’s in the binary representation of each number.
if two numbers have the same amount of 1’s, the shorter string goes first. (ex: “11” goes before “101” when sorting 3 and 5 respectively)
if the amount of 1’s is same, lower decimal number goes first. (ex: 21 = “10101” and 25 = “11001”, then 21 goes first as is lower)

Examples:

Binomial Expansion in Java

Wed, 21 Apr 2021 02:23:20 +0000

The challenge

Write a program that can do some algebra. Write a function expand that takes in an expression with a single, one character variable, and expands it. The expression is in the form (ax+b)^n where a and b are integers which may be positive or negative, x is any single character variable, and n is a natural number. If a = 1, no coefficient will be placed in front of the variable. If a = -1, a “-” will be placed in front of the variable.

Consecutive strings in Java

Tue, 20 Apr 2021 00:18:28 +0000

The challenge

You are given an array(list) strarr of strings and an integer k. Your task is to return the first longest string consisting of k consecutive strings taken in the array.

Examples

strarr = ["tree", "foling", "trashy", "blue", "abcdef", "uvwxyz"], k = 2

Concatenate the consecutive strings of strarr by 2, we get:

treefoling   (length 10)  concatenation of strarr[0] and strarr[1]
folingtrashy ("      12)  concatenation of strarr[1] and strarr[2]
trashyblue   ("      10)  concatenation of strarr[2] and strarr[3]
blueabcdef   ("      10)  concatenation of strarr[3] and strarr[4]
abcdefuvwxyz ("      12)  concatenation of strarr[4] and strarr[5]

Two strings are the longest: "folingtrashy" and "abcdefuvwxyz".
The first that came is "folingtrashy" so 
longest_consec(strarr, 2) should return "folingtrashy".

In the same way:
longest_consec(["zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"], 2) --> "abigailtheta"

n being the length of the string array, if n = 0 or k > n or k <= 0 return “”.

Determine the Highest Scoring Word in Java

Mon, 19 Apr 2021 00:44:31 +0000

The challenge

Given a string of words, you need to find the highest scoring word.

Each letter of a word scores points according to its position in the alphabet: a = 1, b = 2, c = 3 etc.

You need to return the highest scoring word as a string.

If two words score the same, return the word that appears earliest in the original string.

All letters will be lowercase and all inputs will be valid.

Solving Speed Control in Java

Sun, 18 Apr 2021 01:06:55 +0000

The challenge

In John’s car the GPS records every s seconds the distance travelled from an origin (distances are measured in an arbitrary but consistent unit). For example, below is part of a record with s = 15:

x = [0.0, 0.19, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.25]

The sections are:

0.0-0.19, 0.19-0.5, 0.5-0.75, 0.75-1.0, 1.0-1.25, 1.25-1.50, 1.5-1.75, 1.75-2.0, 2.0-2.25

We can calculate John’s average hourly speed on every section and we get:

Calculate Miles per Gallon to Kilometers per Litre in Java

Sat, 17 Apr 2021 00:44:04 +0000

The challenge

Create an application that will display the number of kilometers per liter (output) based on the number of miles per imperial gallon (input).

Make sure to round off the result to two decimal points. If the answer ends with a 0, it should be rounded off without the 0. So instead of 5.50, we should get 5.5.

Some useful associations relevant to this challenge:

1 Imperial Gallon = 4.54609188 litres

How to Convert an Int to a List of Ints in Python

Fri, 16 Apr 2021 00:13:59 +0000

The challenge

Given a non-negative integer, return an array / a list of the individual digits in order.

Examples:

123 => [1,2,3]
1 => [1]
8675309 => [8,6,7,5,3,0,9]

The solution in Python code

Option 1:

def digitize(n):
    return [int(d) for d in str(n)]

Option 2:

def digitize(n):
    return list(map(int, str(n)))

Option 3:

def digitize(n):
    lst = []
    if n == 0:
        return [0]
    while n:
        n,r = divmod(n,10)
        lst.append(r)
    lst.reverse()
    return lst

Test cases to validate our solution

import test
from solution import digitize

@test.describe("Fixed Tests")
def fixed_tests():
    @test.it('Basic Test Cases')
    def basic_test_cases():
        test.assert_equals(digitize(123), [1,2,3])
        test.assert_equals(digitize(1), [1])
        test.assert_equals(digitize(0), [0])
        test.assert_equals(digitize(1230), [1,2,3, 0])
        test.assert_equals(digitize(8675309), [8,6,7,5,3,0,9])

Find the Greatest Common Divisor in Java

Thu, 15 Apr 2021 00:48:52 +0000

The challenge

Find the greatest common divisor of two positive integers. The integers can be large, so you need to find a clever solution.

The inputs x and y are always greater or equal to 1, so the greatest common divisor will always be an integer that is also greater or equal to 1.

The solution in Java code

Option 1 (using Euclidean Algorithm):

public class GCD {
    public static int compute(int x, int y) {
        return (x % y != 0) ? compute(y, x % y) : y;
    }
}

Option 2 (using a loop):

How to Create a Circular List in Python

Wed, 14 Apr 2021 02:04:49 +0000

The challenge

Create a Circular List

A circular list is of finite size, but can infititely be asked for its previous and next elements. This is because it acts like it is joined at the ends and loops around.

For example, imagine a CircularList of [1, 2, 3, 4]. Five invocations of next() in a row should return 1, 2, 3, 4 and then 1 again. At this point, five invocations of prev() in a row should return 4, 3, 2, 1 and then 4 again.

How to Guess the Sequence in Java

Tue, 13 Apr 2021 00:33:00 +0000

The challenge

You must guess a sequence and it has something to do with the number given.

Example

x = 16

result = [1, 10, 11, 12, 13, 14, 15, 16, 2, 3, 4, 5, 6, 7, 8, 9]

The solution in Java code

Option 1:

import java.util.stream.IntStream;

class Challenge {
  static int[] sequence(int x) {
    return IntStream.rangeClosed(1, x)
                .mapToObj(String::valueOf)
                .sorted()
                .mapToInt(Integer::parseInt)
                .toArray();
  } 
}

Option 2:

import java.util.*;
class Challenge {
  static int[] sequence(int x) {
    String arr[] = new String[x];
    for(int i =1;i<=x;i++){
    arr[i-1]= ""+i;
    }
    Arrays.sort(arr);
    int[]  tor =  new int[x];
    for(int i = 0;i<x;i++){
      tor[i] = Integer.parseInt(arr[i]);
    }
    return tor ;
  }
  
}

Option 3:

Reversed sequence in Java

Mon, 12 Apr 2021 01:48:10 +0000

The challenge

Build a function that returns an array of integers from n to 1 where n>0.

Example : n=5 –> [5,4,3,2,1]

The solution in Java code

Option 1:

public class Sequence{

  public static int[] reverse(int n) {
    if (n<=0) return null;
    
    int[] out = new int[n];
    
    for (int i=n, j=0; i>0; i--) {
      out[j] = i;
      j++;
    }
    
    return out;
    
  }

}

Option 2:

import java.util.stream.IntStream;

public class Sequence{

  public static int[] reverse(int n) {
    return IntStream.range(-n, 0).map(Math::abs).toArray();
  }

}

Option 3:

Count the Digit in Java

Sun, 11 Apr 2021 00:53:29 +0000

The challenge

Take an integer n (n >= 0) and a digit d (0 <= d <= 9) as an integer. Square all numbers k (0 <= k <= n) between 0 and n. Count the numbers of digits d used in the writing of all the k**2. Call nb_dig (or nbDig or …) the function taking n and d as parameters and returning this count.

Examples:

n = 10, d = 1, the k*k are 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100
We are using the digit 1 in 1, 16, 81, 100. The total count is then 4.

nb_dig(25, 1):
the numbers of interest are
1, 4, 9, 10, 11, 12, 13, 14, 19, 21 which squared are 1, 16, 81, 100, 121, 144, 169, 196, 361, 441
so there are 11 digits `1` for the squares of numbers between 0 and 25.

Note that 121 has twice the digit 1.

Multiply all elements in an array in Java

Sat, 10 Apr 2021 00:34:24 +0000

The challenge

Create a function multiplyAll/multiply_all which takes an array of integers as an argument. This function must return another function, which takes a single integer as an argument and returns a new array.

The returned array should consist of each of the elements from the first array multiplied by the integer.

Example:

multiplyAll([1, 2, 3])(2) = [2, 4, 6];

You must not mutate the original array.

The solution in Java code

Option 1:

[Solved] Fatal: refusing to merge unrelated histories in Git

Fri, 09 Apr 2021 00:34:11 +0000

You have received the dreaded fatal: refusing to merge unrelated histories error!

You might find yourself asking one of the following questions:

What is refusing to merge unrelated histories?
How do you combine two unrelated histories?
What is unrelated history in git?
How do you fix unrelated branches?

Well look no further, below you will learn how to solve this problem quickly and also learn about why it happens in the first place.

Credit Card Mask in Java

Thu, 08 Apr 2021 00:12:00 +0000

The challenge

Usually when you buy something, you’re asked whether your credit card number, phone number or answer to your most secret question is still correct. However, since someone could look over your shoulder, you don’t want that shown on your screen. Instead, we mask it.

Your task is to write a function maskify, which changes all but the last four characters into '#'.

Examples

Maskify.Maskify("4556364607935616"); // should return "############5616"
Maskify.Maskify("64607935616");      // should return "#######5616"
Maskify.Maskify("1");                // should return "1"
Maskify.Maskify("");                 // should return ""

// "What was the name of your first pet?"
Maskify.Maskify("Skippy");                                   // should return "##ippy"
Maskify.Maskify("Nananananananananananananananana Batman!"); // should return "####################################man!"

The solution in Java code

Option 1:

How to Reverse a Number in Java

Wed, 07 Apr 2021 00:09:10 +0000

The challenge

Given a number, write a function to output its reverse digits. (e.g. given 123 the answer is 321)

Numbers should preserve their sign; i.e. a negative number should still be negative when reversed.

Examples

 123 ->  321
-456 -> -654
1000 ->    1

The solution in Java code

Option 1:

public class ReverseNumber {

  public static int reverse(int number) {
    int result = 0;
    while(number != 0) {
      result = result * 10 + number % 10;
      number = number / 10;
    }
    return result;
  }

}

Option 2:

Positions Average in Java

Tue, 06 Apr 2021 01:11:01 +0000

The challenge

Suppose you have 4 numbers: '0', '9', '6', '4' and 3 strings composed with them:

s1 = "6900690040"
s2 = "4690606946"
s3 = "9990494604"

Compare s1 and s2 to see how many positions they have in common: `` at index 3, 6 at index 4, 4 at index 8 ie 3 common positions out of ten.

Compare s1 and s3 to see how many positions they have in common: 9 at index 1, `` at index 3, 9 at index 5 ie 3 common positions out of ten.

Determine the Date by the Day Number in Java

Mon, 05 Apr 2021 00:26:13 +0000

The challenge

What date corresponds to the nth day of the year?
The answer depends on whether the year is a leap year or not.

Write a function that will help you determine the date if you know the number of the day in the year, as well as whether the year is a leap year or not.
The function accepts the day number and a boolean value isLeap as arguments, and returns the corresponding date of the year as a string "Month, day".
Only valid combinations of a day number and isLeap will be tested.

Correct the time-string in Java

Sun, 04 Apr 2021 01:20:03 +0000

The challenge

You have to create a method, that corrects a given time string.
There was a problem in addition, so many of the time strings are broken.
Time is formatted using the 24-hour clock, so from 00:00:00 to 23:59:59.

Examples

"09:10:01" -> "09:10:01"  
"11:70:10" -> "12:10:10"  
"19:99:99" -> "20:40:39"  
"24:01:01" -> "00:01:01"

The solution in Java code

Option 1:

public class Solution {
 public static String timeCorrect(String timestring) {
    if (timestring == null || !timestring.matches("^\\d{2}:\\d{2}:\\d{2}$")) {
      return null;
    }
    String[] split = timestring.split(":");
    int h = Integer.parseInt(split[0]);
    int m = Integer.parseInt(split[1]);
    int s = Integer.parseInt(split[2]);
    m += s / 60;
    s = s % 60;
    h += m / 60;
    m = m % 60;
    h = h % 24;
    return String.format("%02d:%02d:%02d", h, m, s);
  }
}

Option 2:

Shifter Words Challenge in Java

Sat, 03 Apr 2021 00:07:43 +0000

The challenge

You probably know that some characters written on a piece of paper, after turning this sheet 180 degrees, can be read, although sometimes in a different way. So, uppercase letters “H”, “I”, “N”, “O”, “S”, “X”, “Z” after rotation are not changed, the letter “M” becomes a “W”, and Vice versa, the letter “W” becomes a “M”.

We will call a word “shifter” if it consists only of letters “H”, “I”, “N”, “O”, “S”, “X”, “Z”, “M” and “W”. After turning the sheet, this word can also be read, although in a different way. So, the word “WOW “turns into the word “MOM”. On the other hand, the word “HOME” is not a shifter.

Find Maximum and Minimum Values of a List in Java

Fri, 02 Apr 2021 01:16:04 +0000

The challenge

Make two functions, max and min that take a(n) array/vector of integers list as input and outputs, respectively, the largest and lowest number in that array/vector.

Examples

max({4,6,2,1,9,63,-134,566}) returns 566
min({-52, 56, 30, 29, -54, 0, -110}) returns -110
max({5}) returns 5
min({42, 54, 65, 87, 0}) returns 0

Additionally

You may consider that there will not be any empty arrays/vectors.

The solution in Java code

Option 1:

public class Solution {

  public int min(int[] list) {
    java.util.Arrays.sort(list);
    return list[0];
  }
  
  public int max(int[] list) {
    java.util.Arrays.sort(list);
    return list[list.length-1];
  }
}

Option 2:

Valid Parentheses in Java

Thu, 01 Apr 2021 01:17:18 +0000

The challenge

Write a function that takes a string of parentheses, and determines if the order of the parentheses is valid. The function should return true if the string is valid, and false if it’s invalid.

Examples

"()"              =>  true
")(()))"          =>  false
"("               =>  false
"(())((()())())"  =>  true

Constraints

0 <= input.length <= 100

Along with opening (() and closing ()) parenthesis, input may contain any valid ASCII characters. Furthermore, the input string may be empty and/or not contain any parentheses at all. Do not treat other forms of brackets as parentheses (e.g. [], {}, <>).

Boggle Word Checker in Java

Wed, 31 Mar 2021 00:38:07 +0000

The challenge

Write a function that determines whether a string is a valid guess in a Boggle board, as per the rules of Boggle. A Boggle board is a 2D array of individual characters, e.g.:

[ ['I','L','A','W'],
  ['B','N','G','E'],
  ['I','U','A','O'],
  ['A','S','R','L'] ]

Valid guesses are strings which can be formed by connecting adjacent cells (horizontally, vertically, or diagonally) without re-using any previously used cells.

For example, in the above board “BINGO”, “LINGO”, and “ILNBIA” would all be valid guesses, while “BUNGIE”, “BINS”, and “SINUS” would not.

Build a pile of Cubes in Kotlin

Tue, 30 Mar 2021 00:18:55 +0000

The challenge

Your task is to construct a building which will be a pile of n cubes. The cube at the bottom will have a volume of n^3, the cube above will have volume of (n-1)^3 and so on until the top which will have a volume of 1^3.

You are given the total volume m of the building. Being given m can you find the number n of cubes you will have to build?

Which x for that sum in Kotlin

Mon, 29 Mar 2021 01:16:35 +0000

The challenge

Consider the sequence U(n, x) = x + 2x**2 + 3x**3 + .. + nx**n where x is a real number and n a positive integer.

When n goes to infinity and x has a correct value (ie x is in its domain of convergence D), U(n, x) goes to a finite limit m depending on x.

Usually given x we try to find m. Here we will try to find x (x real, 0 < x < 1) when m is given (m real, m > 0).

Reverse the bits in an integer in Java

Sun, 28 Mar 2021 00:46:04 +0000

The challenge

Write a function that reverses the bits in an integer.

For example, the number 417 is 110100001 in binary. Reversing the binary is 100001011 which is 267.

You can assume that the number is not negative.

The solution in Java code

Option 1:

import static java.lang.Integer.*;

interface BitsOfInteger {
  static int reverse_bits(int n) {
    return parseInt(new StringBuilder(toBinaryString(n)).reverse() + "", 2);
  }
}

Option 2:

public class BitsOfInteger {
  public static int reverse_bits(int n) {
    return Integer.parseInt(new StringBuilder().append(Integer.toBinaryString(n)).reverse().toString(), 2);
  }
}

Option 3:

Invert values in Kotlin

Sat, 27 Mar 2021 01:03:53 +0000

The challenge

Given a set of numbers, return the additive inverse of each. Each positive becomes negatives, and the negatives become positives.

invert([1,2,3,4,5]) == [-1,-2,-3,-4,-5]
invert([1,-2,3,-4,5]) == [-1,2,-3,4,-5]
invert([]) == []

The solution in Kotlin code

Option 1:

fun invert(arr: IntArray) = arr.map { -it }.toIntArray()

Option 2:

fun invert(arr: IntArray): IntArray {
    return IntArray(arr.size){ -arr[it] }
}

Option 3:

fun invert(arr: IntArray): IntArray {
    var x = 0
    while (x < arr.size) {
        arr[x] = arr[x] * -1
        x++
    }
    return arr
}

Test cases to validate our solution

import org.junit.Assert.*;
import org.junit.Test

class TestExample {
  @Test
  fun testFixed() {
    assertArrayEquals(intArrayOf(-1,-2,-3,-4,-5), invert(intArrayOf(1,2,3,4,5)))
    assertArrayEquals(intArrayOf(-1,2,-3,4,-5), invert(intArrayOf(1,-2,3,-4,5)))
    assertArrayEquals(intArrayOf(), invert(intArrayOf()))
    assertArrayEquals(intArrayOf(0), invert(intArrayOf(0)))
  }
}

Spring Boot no main manifest attribute, in

Fri, 26 Mar 2021 01:42:14 +0000

You have created a ./target/.jar and have tried to run it using java -jar <app>.jar yet receive a spring boot no main manifest attribute, in <app>.jar error.

Good thing is that this is really easy to solve!

You can generate your jar as follows instead:

mvn package spring-boot:repackage

Or you could adjust your pom.xml so that you can generate your jar using a simple mvn package:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <mainClass>com.example.Main</mainClass>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Another option is to specify the following parent POM:

Moduli number system in Kotlin

Thu, 25 Mar 2021 00:12:35 +0000

The challenge

A number system with moduli is deﬁned by a vector of k moduli, [m1,m2, ···,mk].

The moduli must be pairwise co-prime, which means that, for any pair of moduli, the only common factor is 1.

In such a system each number n is represented by a string "-x1--x2-- ... --xk-" of its residues, one for each modulus. The product m1 * ... * mk must be greater than the given number n which is to be converted in the moduli number system.

Smallest possible sum in Kotlin

Wed, 24 Mar 2021 00:32:37 +0000

The challenge

Given an array X of positive integers, its elements are to be transformed by running the following operation on them as many times as required:

if X[i] > X[j] then X[i] = X[i] - X[j]

When no more transformations are possible, return its sum (“smallest possible sum”).

For instance, the successive transformation of the elements of input X = [6, 9, 21] is detailed below:

X_1 = [6, 9, 12] # -> X_1[2] = X[2] - X[1] = 21 - 9
X_2 = [6, 9, 6]  # -> X_2[2] = X_1[2] - X_1[0] = 12 - 6
X_3 = [6, 3, 6]  # -> X_3[1] = X_2[1] - X_2[0] = 9 - 6
X_4 = [6, 3, 3]  # -> X_4[2] = X_3[2] - X_3[1] = 6 - 3
X_5 = [3, 3, 3]  # -> X_5[1] = X_4[0] - X_4[1] = 6 - 3

The returning output is the sum of the final transformation (here 9).

Floating-point Approximation in Kotlin

Tue, 23 Mar 2021 00:01:12 +0000

The challenge

Given

a semi-inclusive interval I = [l, u) (l is in interval I but u is not) l and u being floating numbers (0 <= l < u),
an integer n (n > 0)
a function f: x (float number) -> f(x) (float number)

we want to return as a list the n values:

f(l), f(l + d), ..., f(u -d) where d = (u - l) / n

Multiplication table in Kotlin

Mon, 22 Mar 2021 01:03:52 +0000

The challenge

Create an NxN multiplication table, of size provided in parameter.

for example, when given size is 3:

1 2 3
2 4 6
3 6 9

for given example, the return value should be: [[1,2,3],[2,4,6],[3,6,9]]

The solution in Kotlin

Option 1:

package solution

object Solution {
    fun multiplicationTable(size: Int) = Array<IntArray>(size) {
        i -> (1..size).map { it * (i + 1) }.toIntArray()
    }
}

Option 2:

package solution

object Solution {
    fun multiplicationTable(size: Int): Array<IntArray> {
        return Array(size){i -> IntArray(size){(it + 1) * (i + 1)}}
    }
}

Option 3:

Strip Comments in Kotlin

Sun, 21 Mar 2021 00:32:45 +0000

The challenge

Complete the solution so that it strips all text that follows any of a set of comment markers passed in. Any whitespace at the end of the line should also be stripped out.

Example:

Given an input string of:

apples, pears # and bananas
grapes
bananas !apples

The output expected would be:

apples, pears
grapes
bananas

The code would be called like so:

var result = solution("apples, pears # and bananas\ngrapes\nbananas !apples", charArrayOf('#', '!'))
// result should == "apples, pears\ngrapes\nbananas"

The solution in Kotlin

Option 1:

Experimenting with a sequence of complex numbers in Kotlin

Sat, 20 Mar 2021 00:13:17 +0000

The challenge

Consider the sequence S(n, z) = (1 - z)(z + z**2 + z**3 + ... + z**n) where z is a complex number and n a positive integer (n > 0).

When n goes to infinity and z has a correct value (ie z is in its domain of convergence D), S(n, z) goes to a finite limit lim depending on z.

Experiment with S(n, z) to guess the domain of convergence Dof S and lim value when z is in D.

pt-online-schema-change Add Index

Fri, 19 Mar 2021 02:02:48 +0000

Percona has a great toolkit that allows you to perform schema changes on a MySQL or MariaDB database without any downtime, it works by creating a new table with the same schema, making the changes to it and applying triggers for insertion, deletion and all updates, all while performing your valuable schema updates for you!

How to Add an Index to a MySQL or MariaDB database without downtime

pt-online-schema-change --alter 'add index ix_<COLUMN_NAME> (<COLUMN_NAME>)' D=<DATABASE_NAME>,t=<TABLE_NAME> --dry-run

Sums of Parts in Kotlin

Thu, 18 Mar 2021 01:26:54 +0000

The challenge

Let us consider this example (array written in general format):

ls = [0, 1, 3, 6, 10]

Its following parts:

ls = [0, 1, 3, 6, 10]
ls = [1, 3, 6, 10]
ls = [3, 6, 10]
ls = [6, 10]
ls = [10]
ls = []

The corresponding sums are (put together in a list): [20, 20, 19, 16, 10, 0]

The function parts_sums (or its variants in other languages) will take as parameter a list ls and return a list of the sums of its parts as defined above.

Diophantine Equation in Kotlin

Wed, 17 Mar 2021 01:52:37 +0000

The challenge

In mathematics, a Diophantine equation is a polynomial equation, usually with two or more unknowns, such that only the integer solutions are sought or studied.

In this challenge we want to find all integers x, y (x >= 0, y >= 0) solutions of a diophantine equation of the form:

x2 – 4 * y2 = n

(where the unknowns are x and y, and n is a given positive number) in decreasing order of the positive xi.

Matrix Addition in Java

Tue, 16 Mar 2021 00:15:33 +0000

The challenge

Write a function that accepts two square matrices (N x N two dimensional arrays), and return the sum of the two. Both matrices being passed into the function will be of size N x N (square), containing only integers.

How to sum two matrices:

Take each cell [n][m] from the first matrix, and add it with the same [n][m] cell from the second matrix. This will be cell [n][m] of the solution matrix.

Numbers that are a power of their sum of digits in Java

Mon, 15 Mar 2021 00:18:55 +0000

The challenge

The number 81 has a special property, a certain power of the sum of its digits is equal to 81 (nine squared). Eighty one (81), is the first number in having this property (not considering numbers of one digit). The next one, is 512. Let’s see both cases with the details

8 + 1 = 9 and 92 = 81

Integer triangles in Java

Sun, 14 Mar 2021 01:36:29 +0000

The challenge

You have to give the number of different integer triangles with one angle of 120 degrees which perimeters are under or equal a certain value. Each side of an integer triangle is an integer value.

// number of integer triangles,
give_triang(max. perimeter)

with sides a, b, and c integers such that:

a + b + c <= max. perimeter

See some of the following cases

// No Integer triangles with perimeter under or equal five
give_triang(5) // 0

// One integer triangle of (120 degrees). It's (3, 5, 7)
give_triang(15) // 1

// Three triangles: (3, 5, 7), (6, 10, 14) and (7, 8, 13)
give_triang(30) // 3

// (3, 5, 7), (5, 16, 19), (6, 10, 14), (7, 8, 13) and (9, 15, 21) are the triangles with perim under or equal 50.
give_triang(50) // 5

The solution in Java code

Option 1:

Minimum path in squares in Java

Sat, 13 Mar 2021 01:49:30 +0000

The challenge

You’re given a square consisting of random numbers, like so:

var square = [
    [1,2,3],
    [4,8,2],
    [1,5,3]
];

Your job is to calculate the minimum total cost when moving from the upper left corner to the coordinate given. You’re only allowed to move right or down.

In the above example the minimum path would be:

var square = [
    [1,2,3],
    [_,_,2],
    [_,_,3]
];

Giving a total of 11. Start and end position are included.

Pascal’s Diagonals in Java

Fri, 12 Mar 2021 00:05:17 +0000

The challenge

Create a function that returns an array containing the first l digits from the nth diagonal of Pascal’s triangle.

n = 0 should generate the first diagonal of the triangle (the ‘ones’). The first number in each diagonal should be 1.

If l = 0, return an empty array. Assume that both n and l will be non-negative integers in all test cases.

Maximum Contiguous Sum in Java

Thu, 11 Mar 2021 01:22:05 +0000

The challenge

Given an unsorted array of integer values, find the maximum positive sum of any contiguous range within the array.

An array containing only negative values can return 0. Your solution should be efficient enough to not throw a timeout exception.

Example:

// returns 24
maxContiguousSum([3, -4, 8, 7, -10, 19, -3]);

// returns 5
maxContiguousSum([-8, -10, -12, -2, -3, 5]);

Visual example:

[3, -4, 8, 7, -10, 19, -3]
       |_____________|
             ||
             \/
             24

The solution in Java code

Option 1:

Fibonacci Streaming in Java

Wed, 10 Mar 2021 00:03:12 +0000

The challenge

You’re going to provide a needy programmer a utility method that generates an infinite sized, sequential IntStream which contains all the numbers in a fibonacci sequence.

A fibonacci sequence starts with two 1s. Every element afterwards is the sum of the two previous elements. See:

1, 1, 2, 3, 5, 8, 13, ..., 89, 144, 233, 377, ...

The solution in Java code

Option 1:

import java.util.function.IntSupplier;
import java.util.stream.IntStream;

public class Utility {

    public static IntStream generateFibonacciSequence() {
        return IntStream.generate(new IntSupplier() {
            int a = 0;
            int b = 1;

            @Override
            public int getAsInt() {
                int x = a + b;
                a = b;
                b = x;
                return a;
            }
        });
    }
}

Option 2:

Base-2 in Java

Tue, 09 Mar 2021 02:06:06 +0000

The challenge

In this challenge you must convert integers numbers from and to a negative-base binary system.

Negative-base systems can accommodate all the same numbers as standard place-value systems, but both positive and negative numbers are represented without the use of a minus sign (or, in computer representation, a sign bit); this advantage is countered by an increased complexity of arithmetic operations.

To help understand, the first eight digits (in decimal) of the Base(-2) system is:

Unique digits sequence in Java

Mon, 08 Mar 2021 09:20:57 +0000

The challenge

Consider the following series:

0,1,2,3,4,5,6,7,8,9,10,22,11,20,13,24...There is nothing special between numbers `` and 10.

Let’s start with the number 10 and derive the sequence. 10 has digits 1 and . The next possible number that does not have a `1` or a  is 22. All other numbers between 10 and 22 have a 1 or a ``.

From 22, the next number that does not have a 2 is 11. Note that 30 is also a possibility because it is the next higher number that does not have a 2, but we must select the lowest number that fits and is not already in the sequence.

Palindrome integer composition in Java

Sun, 07 Mar 2021 01:07:31 +0000

The challenge

The palindromic number 595 is interesting because it can be written as the sum of consecutive squares: 6^2 + 7^2 + 8^2 + 9^2 + 10^2 + 11^2 + 12^2 = 595.

There are exactly eleven palindromes below one-thousand that can be written as consecutive square sums. Note that 1 = 0^2 + 1^2 has not been included as this problem is concerned with the squares of positive integers.

Count IP Addresses in Java

Sat, 06 Mar 2021 00:28:26 +0000

The challenge

Implement a function that receives two IPv4 addresses, and returns the number of addresses between them (including the first one, excluding the last one).

All inputs will be valid IPv4 addresses in the form of strings. The last address will always be greater than the first one.

Examples

ips_between("10.0.0.0", "10.0.0.50")  ==   50 
ips_between("10.0.0.0", "10.0.1.0")   ==  256 
ips_between("20.0.0.10", "20.0.1.0")  ==  246

The solution in Java code

Option 1:

public class CountIPAddresses {

  public static long ipsBetween(String start, String end) {
    return convertToLong(end) - convertToLong(start);
  }
  
  private static long convertToLong(String ip) {
    long res = 0;
    for (String s : ip.split("[.]") )
      res = res * 256 + Long.parseLong(s);
    return res;
  }
}

Option 2:

Shortest Knight Path in Java

Fri, 05 Mar 2021 01:11:09 +0000

The challenge

Given two different positions on a chess board, find the least number of moves it would take a knight to get from one to the other. The positions will be passed as two arguments in algebraic notation. For example, knight("a3", "b5") should return 1.

The knight is not allowed to move off the board. The board is 8×8.

For information on knight moves, see https://en.wikipedia.org/wiki/Knight_%28chess%29

All Balanced Parentheses in Java

Thu, 04 Mar 2021 02:13:33 +0000

The challenge

Write a function that makes a list of strings representing all of the ways you can balance n pairs of parentheses

Examples

balancedParens(0) returns ArrayList<String> with element:  ""
balancedParens(1) returns ArrayList<String> with element:  "()"
balancedParens(2) returns ArrayList<String> with elements: "()()","(())"
balancedParens(3) returns ArrayList<String> with elements: "()()()","(())()","()(())","(()())","((()))"

The solution in Java code

Option 1:

import java.util.ArrayList;

public class BalancedParens {

    public static ArrayList <String> balancedParens (int n) {
        ArrayList<String> lst = new ArrayList<>();
        StringBuilder sb = new StringBuilder();
        dfs(sb,lst,0,0,n);
        return lst;
    }
    
    private static void dfs(StringBuilder sb, ArrayList<String> lst, int open, int close, int max) {
        if (close==max) {
            lst.add(sb.toString());
            return;
        }
        if (open>close)  {
            sb.append(')');
            dfs(sb,lst,open,close+1,max);
            sb.deleteCharAt(sb.length()-1);
        }
        if (open<max) {
            sb.append('(');
            dfs(sb,lst,open+1,close,max);
            sb.deleteCharAt(sb.length()-1);
        }
    }
}

Option 2:

Human readable duration format in Java

Wed, 03 Mar 2021 02:40:07 +0000

The challenge

Your task in order to complete this challenge is to write a function which formats a duration, given as a number of seconds, in a human-friendly way.

The function must accept a non-negative integer. If it is zero, it just returns "now". Otherwise, the duration is expressed as a combination of years, days, hours, minutes and seconds.

It is much easier to understand with an example:

//returns "1 minute and 2 seconds"
TimeFormatter.formatDuration(62)

//returns "1 hour, 1 minute and 2 seconds"
TimeFormatter.formatDuration(3662)

For the purpose of this challenge, a year is 365 days and a day is 24 hours.

Simple string expansion in Java

Tue, 02 Mar 2021 00:49:22 +0000

The challenge

Consider the following expansion:

// because "ab" repeats 3 times
solve("3(ab)") == "ababab"

// because "a3(b)" == "abbb", which repeats twice.
solve("2(a3(b))") == "abbbabbb"

Given a string, return the expansion of that string.

Input will consist of only lowercase letters and numbers (1 to 9) in valid parenthesis. There will be no letters or numbers after the last closing parenthesis.

The solution in Java code

Option 1:

class Solution{
    public static String solve(String s){
        String new_s = "";
        for(char ch : new StringBuilder(s).reverse().toString().toCharArray()) {
          if(Character.isDigit(ch)) new_s = new_s.repeat(Integer.parseInt(ch + ""));
          if(Character.isLetter(ch)) new_s = ch + new_s; 
        }
        return new_s;
    }
}

Option 2:

Hamming Numbers in Java

Mon, 01 Mar 2021 02:14:22 +0000

The challenge

A Hamming number is a positive integer of the form 2i3j5k, for some non-negative integers i, j, and k.

Block sequence in Java

Sun, 28 Feb 2021 00:34:57 +0000

The challenge

Consider the following array:

[1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891011...]

If we join these blocks of numbers, we come up with an infinite sequence which starts with 112123123412345123456.... The list is infinite.

You will be given an number (n) and your task will be to return the element at that index in the sequence, where 1 ≤ n ≤ 10^18. Assume the indexes start with 1, not ``. For example:

Roman Numerals Helper in Java

Sat, 27 Feb 2021 00:44:15 +0000

The challenge

Create a RomanNumerals class that can convert a roman numeral to and from an integer value. It should follow the API demonstrated in the examples below. Multiple roman numeral values will be tested for each helper method.

Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.

Closest pair of points in linearithmic time in Java

Fri, 26 Feb 2021 01:03:36 +0000

The challenge

Given a number of points on a plane, your task is to find two points with the smallest distance between them in linearithmic O(n log n) time.

Example

  1  2  3  4  5  6  7  8  9
1  
2    . A
3                . D
4                   . F       
5             . C
6              
7                . E
8    . B
9                   . G

For the plane above, the input will be:

Find sum of top-left to bottom-right diagonals in Java

Thu, 25 Feb 2021 00:25:06 +0000

The challenge

Given a square matrix (i.e. an array of subarrays), find the sum of values from the first value of the first array, the second value of the second array, the third value of the third array, and so on…

Examples

array = [[1, 2],
         [3, 4]]

diagonal sum: 1 + 4 = 5

array = [[5, 9, 1, 0],
         [8, 7, 2, 3],
         [1, 4, 1, 9],
         [2, 3, 8, 2]]

diagonal sum: 5 + 7 + 1 + 2 = 15

The solution in Java code

Option 1:

Sweeping trees in Java

Wed, 24 Feb 2021 00:02:18 +0000

The challenge

You will be given a list of strings representing nodes in a rooted tree. A visual representation of a very simple rooted tree could be:

        +----+
        |root|
        ++--++
         |  |
    +----+  +----+
    v            v
+------+      +------+
|node A|      |node B|
+------+      +------+

In this case, the root node has two children, nodes A and B. A more complex example would be:

Detect Pangram in Java

Tue, 23 Feb 2021 00:51:39 +0000

The challenge

A pangram is a sentence that contains every single letter of the alphabet at least once. For example, the sentence “The quick brown fox jumps over the lazy dog” is a pangram, because it uses the letters A-Z at least once (case is irrelevant).

Given a string, detect whether or not it is a pangram. Return True if it is, False if not. Ignore numbers and punctuation.

The solution in Java code

Option 1 (using a Character loop):

Remove the parentheses in Java

Mon, 22 Feb 2021 00:08:07 +0000

The challenge

In this challenge you are given a string for example:

"example(unwanted thing)example"

Your task is to remove everything inside the parentheses as well as the parentheses themselves.

The example above would return:

"exampleexample"

Notes

Other than parentheses only letters and spaces can occur in the string. Don’t worry about other brackets like "[]" and "{}" as these will never appear.
There can be multiple parentheses.
The parentheses can be nested.

The solution in Java code

Option 1:

What century is it in Java

Sun, 21 Feb 2021 00:25:29 +0000

The challenge

Return the century of the input year. The input will always be a 4 digit string, so there is no need for validation.

Examples

"1999" --> "20th"
"2011" --> "21st"
"2154" --> "22nd"
"2259" --> "23rd"
"1124" --> "12th"
"2000" --> "20th"

The solution in Java code

Option 1:

public class Solution{
  public static String whatCentury(int year) {
    int century = (year + 99) / 100;
    if (century / 10 == 1) return century + "th";
    switch(century % 10) {
      case 1: return century + "st";
      case 2: return century + "nd";
      case 3: return century + "rd";
      default: return century + "th";
    }
   }
}

Option 2:

Lost number in number sequence in Java

Sat, 20 Feb 2021 01:12:37 +0000

The challenge

An ordered sequence of numbers from 1 to N is given. One number might have deleted from it, then the remaining numbers were mixed. Find the number that was deleted.

Example:

The starting array sequence is [1,2,3,4,5,6,7,8,9]
The mixed array with one deleted number is [3,2,4,6,7,8,1,9]
Your function should return the int 5.

If no number was deleted from the array and no difference with it, your function should return the int ``.

Simple string reversal in Java

Fri, 19 Feb 2021 02:07:34 +0000

The challenge

In this challenge, we are going to reverse a string while maintaining the spaces (if any) in their original place.

For example:

solve("our code") = "edo cruo"
-- Normal reversal without spaces is "edocruo". 
-- However, there is a space at index 3, so the string becomes "edo cruo"

solve("your code rocks") = "skco redo cruoy". 
solve("andrew") = "werdna"

More examples in the test cases. All input will be lower case letters and in some cases spaces.

int32 to IPv4 in Java

Thu, 18 Feb 2021 01:44:32 +0000

The challenge

Take the following IPv4 address: 128.32.10.1

This address has 4 octets where each octet is a single byte (or 8 bits).

1st octet 128 has the binary representation: 10000000
2nd octet 32 has the binary representation: 00100000
3rd octet 10 has the binary representation: 00001010
4th octet 1 has the binary representation: 00000001

So 128.32.10.1 == 10000000.00100000.00001010.00000001

Because the above IP address has 32 bits, we can represent it as the unsigned 32-bit number: 2149583361

Perimeter of squares in a rectangle in Java

Wed, 17 Feb 2021 01:13:31 +0000

The challenge

The drawing shows 6 squares the sides of which have a length of 1, 1, 2, 3, 5, 8. It’s easy to see that the sum of the perimeters of these squares is : 4 * (1 + 1 + 2 + 3 + 5 + 8) = 4 * 20 = 80

Could you give the sum of the perimeters of all the squares in a rectangle when there are n + 1 squares disposed in the same manner as in the drawing:

Palindrome chain length in Java

Tue, 16 Feb 2021 00:06:46 +0000

The challenge

Number is a palindrome if it is equal to the number with digits in reversed order. For example, 5, 44, 171, 4884 are palindromes, and 43, 194, 4773 are not.

Write a function which takes a positive integer and returns the number of special steps needed to obtain a palindrome. The special step is: “reverse the digits, and add to the original number”. If the resulting number is not a palindrome, repeat the procedure with the sum until the resulting number is a palindrome.

String array duplicates in Java

Mon, 15 Feb 2021 00:28:47 +0000

The challenge

You are given an array of strings and your task is to remove all consecutive duplicate letters from each string in the array.

For example:

dup(["abracadabra","allottee","assessee"]) = ["abracadabra","alote","asese"].
dup(["kelless","keenness"]) = ["keles","kenes"].

Strings will be lowercase only, no spaces. See test cases for more examples.

The solution in Java code

Option 1 (using StringBuilders):

class Solution{    
    public static String[] dup(String[] arr){
        String[] strings = new String[arr.length];

        for (int h = 0; h < arr.length; h++) {

            String str = arr[h];

            StringBuilder sb = new StringBuilder();
            char current = 0;
            char last = 0;
            for (int i = 0; i < str.length(); i++) {
                current = str.charAt(i);
                if (current!=last) sb.append(current);
                last = current;
            }
            strings[h] = sb.toString();

        }

        return strings;
    }
}

Option 2 (reusing the input array):

Even or Odd Array Sum in Java

Sun, 14 Feb 2021 00:16:34 +0000

The challenge

Given a list of numbers, determine whether the sum of its elements is odd or even.

Give your answer as a string matching "odd" or "even".

If the input array is empty consider it as: [0] (array with a zero).

Example:

odd_or_even([0])          ==  "even"
odd_or_even([0, 1, 4])    ==  "odd"
odd_or_even([0, -1, -5])  ==  "even"

The solution in Java code

Option 1 (using streams):

public class Solution {
  public static String oddOrEven (int[] array) {
    return (java.util.Arrays.stream(array).sum()%2==0) 
      ? "even" : "odd";
  }
}

Option 2 (using forloop):

String Permutations in Java

Sat, 13 Feb 2021 00:04:28 +0000

The challenge

In this challenge, you have to create all permutations of an input string and remove duplicates if present. This means you have to shuffle all letters from the input in all possible orders.

Examples:

Permutations.singlePermutations("a") // ["a"]
Permutations.singlePermutations("ab") // ["ab", "ba"]
Permutations.singlePermutations("aabb") // ["aabb","abab","abba","baab","baba","bbaa"]

The order of the permutations doesn’t matter.

The solution in Java code

Option 1:

import static java.util.Collections.singletonList;
import static java.util.stream.Collectors.toList;

import java.util.List;

class Permutations {

  public static List<String> singlePermutations(final String s) {
    return permute("", s);
  }

  private static List<String> permute(final String prefix, final String s) {
  
    return s.isEmpty()
        ? singletonList(prefix)
        : s.chars()
            .distinct()
            .mapToObj(i -> (char) i)
            .map(c -> permute(prefix + c, takeOut(s, c)))
            .flatMap(List::stream)
            .collect(toList());
  }

  static String takeOut(final String s, final char c) {
    final int i = s.indexOf(c);
    return s.substring(0, i) + s.substring(i + 1);
  }
}

Option 2:

Remove a Specific Element of an Array in Java

Fri, 12 Feb 2021 00:01:17 +0000

The challenge

You will be given a certain array of length n, such that n > 4, having positive and negative integers but there will be no zeroes and all the elements will occur once in it.

We may obtain an amount of n sub-arrays of length n - 1, removing one element at a time (from left to right).

For each subarray, let’s calculate the product and sum of its elements with the corresponding absolute value of the quotient, q = SubProduct/SubSum (if it is possible, SubSum cannot be 0). Then we select the array with the lowest value of |q|(absolute value)

Upside down numbers in Java

Thu, 11 Feb 2021 02:41:33 +0000

The challenge

Consider the numbers 6969 and 9116. When you rotate them 180 degrees (upside down), these numbers remain the same. To clarify, if we write them down on a paper and turn the paper upside down, the numbers will be the same. Try it and see! Some numbers such as 2 or 5 don’t yield numbers when rotated.

Given a range, return the count of upside down numbers within that range. For example, solve(0,10) = 3, because there are only 3 upside down numbers >= 0 and < 10. They are 0, 1, 8.

Rotate matrix counter-clockwise N times in Java

Wed, 10 Feb 2021 00:59:56 +0000

The challenge

In this challenge your mission is to rotate matrix counter-clockwise N times.

So, you will have 2 inputs:

1) matrix

2) a number, how many times to turn it

And the output is turned matrix.

Example:

matrix = [[1, 2, 3, 4],
          [5, 6, 7, 8],
          [9, 10, 11, 12],
          [13, 14, 15, 16]]

times_to_turn = 1

It should return this:

[[4, 8, 12, 16],
 [3, 7, 11, 15],
 [2, 6, 10, 14],
 [1, 5, 9, 13]])

Note: all matrixes will be square. Also, random tests will have big numbers in the input (times to turn)

Unable to import module “lambda_function”: No module named “pymysql”

Tue, 09 Feb 2021 01:21:07 +0000

If you receive the following error message when trying to run pymysql on AWS Lambda:

Unable to import module "lambda_function": No module named "pymysql" then you can fix this by running a Custom Lambda Layer.

To do this, you can boot up an EC2 instance (or a Linux instance anywhere else) and run the following set of commands:

#create module directory
mkdir -p temp/python
cd temp/python

#install pymysql module
pip install pymysql -t .
cd ..

#create a zip file using installed module
zip -r9 ../pymysql.zip .

#create the lambda layer
aws lambda publish-layer-version --layer-name pymysql \
--description "pymysql for mysql access" \
--zip-file fileb://../pymysql.zip \
--compatible-runtimes python3.8

Once this is done, you will be able to head back to AWS Lambda, click on Layers and view your custom layer waiting there for you to use!

Square Matrix Multiplication in Java

Mon, 08 Feb 2021 00:21:56 +0000

The challenge

Write a function that accepts two square (NxN) matrices (two dimensional arrays), and returns the product of the two. Only square matrices will be given.

How to multiply two square matrices:

We are given two matrices, A and B, of size 2×2 (note: tests are not limited to 2×2). Matrix C, the solution, will be equal to the product of A and B. To fill in cell [0][0] of matrix C, you need to compute: A[0][0] * B[0][0] + A[0][1] * B[1][0].

Count the divisible numbers in Java

Sun, 07 Feb 2021 01:24:08 +0000

The challenge

Complete the function that takes 3 numbers x, y and k (where x ≤ y), and returns the number of integers within the range [x..y] (both ends included) that are divisible by k.

More scientifically: { i : x ≤ i ≤ y, i mod k = 0 }

Example

Given x = 6, y = 11, k = 2 the function should return 3, because there are three numbers divisible by 2 between 6 and 11: 6, 8, 10

Averages of numbers in Java

Sat, 06 Feb 2021 00:47:04 +0000

The challenge

Get the averages of these numbers

Write a method, that gets an array of integer-numbers and return an array of the averages of each integer-number and his follower, if there is one.

Example:

Input:  [ 1, 3, 5, 1, -10]
Output:  [ 2, 4, 3, -4.5]

If the array has 0 or 1 values or is null, your method should return an empty array.

The solution in Java code

Option 1:

Decimal to Factorial and Back in Java

Fri, 05 Feb 2021 01:49:05 +0000

The challenge

Coding decimal numbers with factorials is a way of writing out numbers in a base system that depends on factorials, rather than powers of numbers.

In this system, the last digit is always `` and is in base 0!. The digit before that is either 0 or 1 and is in base 1!. The digit before that is either 0, 1, or 2 and is in base 2!, etc. More generally, the nth-to-last digit is always 0, 1, 2, ..., n and is in base n!.

Vowel Count in Java

Thu, 04 Feb 2021 00:07:16 +0000

The challenge

Return the number (count) of vowels in the given string.

We will consider a, e, i, o, u as vowels for this challenge (but not y).

The input string will only consist of lower case letters and/or spaces.

The solution in Java code

Option 1:

public class Vowels {

  public static int getCount(String str) {
    int vowelsCount = 0;
    char[] chars = str.toCharArray();
    for (char c : chars) {
      if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u')
        vowelsCount++;
    }
    return vowelsCount;
  }

}

Option 2:

Equal Sides Of An Array in Java

Wed, 03 Feb 2021 00:47:00 +0000

The challenge

You are going to be given an array of integers. Your job is to take that array and find an index N where the sum of the integers to the left of N is equal to the sum of the integers to the right of N. If there is no index that would make this happen, return -1.

For example:

Let’s say you are given the array {1,2,3,4,3,2,1}:
Your function will return the index 3, because at the 3rd position of the array, the sum of left side of the index ({1,2,3}) and the sum of the right side of the index ({3,2,1}) both equal 6.

Largest 5 digit number in a series in Java

Tue, 02 Feb 2021 00:27:57 +0000

The challenge

In the following 6 digit number:

91 is the greatest sequence of 2 consecutive digits.

In the following 10 digit number:

1234567890

67890 is the greatest sequence of 5 consecutive digits.

Complete the solution so that it returns the greatest sequence of five consecutive digits found within the number given. The number will be passed in as a string of only digits. It should return a five-digit integer. The number passed may be as large as 1000 digits.

Next smaller number with the same digits in Java

Mon, 01 Feb 2021 01:06:54 +0000

The challenge

Write a function that takes a positive integer and returns the next smaller positive integer containing the same digits.

For example:

nextSmaller(21) == 12
nextSmaller(531) == 513
nextSmaller(2071) == 2017

Return -1 (for Haskell: return Nothing, for Rust: return None), when there is no smaller number that contains the same digits. Also return -1 when the next smaller number with the same digits would require the leading digit to be zero.

Count of positives / sum of negatives in Java

Sun, 31 Jan 2021 01:30:36 +0000

The challenge

Given an array of integers.

Return an array, where the first element is the count of positives numbers and the second element is sum of negative numbers.

If the input array is empty or null, return an empty array.

Example

For input [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, -11, -12, -13, -14, -15], you should return [10, -65].

The solution in Java code

Option 1:

Find the stray number in Java

Sat, 30 Jan 2021 00:55:45 +0000

The challenge

You are given an odd-length array of integers, in which all of them are the same, except for one single number.

Complete the method which accepts such an array, and returns that single different number.

The input array will always be valid! (odd-length >= 3)

Examples

[1, 1, 2] ==> 2
[17, 17, 3, 17, 17, 17, 17] ==> 3

The solution in Java code

Option 1:

import java.util.*;

class Solution {
  static int stray(int[] numbers) {
    Map<Integer, Integer> map = new HashMap<>();
    
    for (int i=0; i<numbers.length; i++) {
      Integer def = map.getOrDefault(numbers[i], 0);
      map.put(numbers[i], ++def);
    }
    
    for(Integer key : map.keySet()) {
      System.out.println(key);
      System.out.println(map.get(key));
      if (map.get(key)==1) return key;
    }
    
    return 0;
  }
}

Option 2:

4 By 4 Skyscrapers in Java

Fri, 29 Jan 2021 00:15:19 +0000

The challenge

In a grid of 4 by 4 squares you want to place a skyscraper in each square with only some clues:

The height of the skyscrapers is between 1 and 4
No two skyscrapers in a row or column may have the same number of floors
A clue is the number of skyscrapers that you can see in a row or column from the outside
Higher skyscrapers block the view of lower skyscrapers located behind them

Can you write a program that can solve this puzzle?

How to Fix: package org.junit.jupiter.api does not exist

Thu, 28 Jan 2021 01:34:44 +0000

The problem

If you have received the package org.junit.jupiter.api deos not exist error when trying to run a JUnit Java Test with Maven, it’s because of a missing dependency in your pom.xml file.

The solution

Add the following dependency entry to your pom.xml file:

<dependencies>

    <!-- add the junit dependency here -->
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>5.7.0</version>
        <scope>test</scope>
    </dependency>

</dependencies>

How to Programmatically Filter ag-Grid Columns in Angular

Wed, 27 Jan 2021 00:30:52 +0000

You can easily control the column filtering in ag-Grid by using the getFilterInstance and setModel methods associated to the column you need filtering. Once done, remember to call onFilterChanged to apply your changes.

// a list of all your items you want to filter
// make sure to create a list of strings
// a list of numbers won't work
const listOfItems = data.map((row) => row.ComeColumnItem.toString())

// get the filter instance per column
const filterInstance = this.gridApi?.getFilterInstance('YourColumnName')

// get the existing model in-case you want to modify it
const model = this.gridApi?.getModel()

// or set a new one
filterInstance?.setModel({
  type: 'set',
  values: listOfItems
})

// remember to apply the changes when done!
this.gridApi?.onFilterChanged()

Sum by Factors in Java

Tue, 26 Jan 2021 00:26:26 +0000

The challenge

Given an array of positive or negative integers

I= [i1,..,in]

you have to produce a sorted array P of the form

[ [p, sum of all ij of I for which p is a prime factor (p positive) of ij] ...]

P will be sorted by increasing order of the prime numbers. The final result has to be given as a string in Java, C#, C, C++ and as an array of arrays in other languages.

Count the divisors of a number in Java

Mon, 25 Jan 2021 00:36:32 +0000

The challenge

Count the number of divisors of a positive integer n.

Random tests go up to n = 500000.

Examples

numberOfDivisors(4)  == 3 // 1, 2, 4
numberOfDivisors(5)  == 2 // 1, 5
numberOfDivisors(12) == 6 // 1, 2, 3, 4, 6, 12
numberOfDivisors(30) == 8 // 1, 2, 3, 5, 6, 10, 15, 30

The solution in Java code

Option 1:

public class FindDivisor {

  public long numberOfDivisors(int n) {
      long counter = 0;
      for(int i=1; i<=n; i++){
          if(n % i == 0){
          counter++;
          }
      }
      return counter;
  }
}

Option 2:

My smallest code interpreter in Java

Sun, 24 Jan 2021 00:21:24 +0000

The challenge

Inspired from real-world Brainf**k, we want to create an interpreter of that language which will support the following instructions:

> increment the data pointer (to point to the next cell to the right).
< decrement the data pointer (to point to the next cell to the left).
+ increment (increase by one, truncate overflow: 255 + 1 = 0) the byte at the data pointer.
- decrement (decrease by one, treat as unsigned byte: 0 – 1 = 255 ) the byte at the data pointer.
. output the byte at the data pointer.
, accept one byte of input, storing its value in the byte at the data pointer.
[ if the byte at the data pointer is zero, then instead of moving the instruction pointer forward to the next command, jump it forward to the command after the matching ] command.
] if the byte at the data pointer is nonzero, then instead of moving the instruction pointer forward to the next command, jump it back to the command after the matching [ command.

The function will take in input…

Pick peaks in Java

Sat, 23 Jan 2021 01:23:00 +0000

The challenge

Write a function that returns the positions and the values of the “peaks” (or local maxima) of a numeric array.

For example, the array arr = [0, 1, 2, 5, 1, 0] has a peak at position 3 with a value of 5 (since arr[3] equals 5).

The output will be returned as a “Map<String,List>with two key-value pairs:“pos”and“peaks”. If there is no peak in the given array, simply return{“pos” => [], “peaks” => []}`.

Number of trailing zeros of N in Java

Fri, 22 Jan 2021 03:59:19 +0000

The challenge

Write a program that will calculate the number of trailing zeros in a factorial of a given number.

N! = 1 * 2 * 3 * ... * N

Be careful 1000! has 2568 digits…

For more info, see: http://mathworld.wolfram.com/Factorial.html

Examples

zeros(6) = 1
// 6! = 1 * 2 * 3 * 4 * 5 * 6 = 720 --> 1 trailing zero

zeros(12) = 2
// 12! = 479001600 --> 2 trailing zeros

The solution in Java code

Option 1:

Alphabetic Anagrams in Java

Thu, 21 Jan 2021 00:41:30 +0000

The challenge

Consider a “word” as any sequence of capital letters A-Z (not limited to just “dictionary words”). For any word with at least two different letters, there are other words composed of the same letters but in a different order (for instance, STATIONARILY/ANTIROYALIST, which happen to both be dictionary words; for our purposes “AAIILNORSTTY” is also a “word” composed of the same letters as these two).

We can then assign a number to every word, based on where it falls in an alphabetically sorted list of all words made up of the same group of letters. One way to do this would be to generate the entire list of words and find the desired one, but this would be slow if the word is long.

Remove file from Git without deleting locally

Wed, 20 Jan 2021 00:41:51 +0000

If you find yourself in a position where you have already committed some files to git, and they are in the remote repository already, but you want to remove them from you repository without deleting them locally, you can do the following:

Introducing the git rm --cached command:

Remove a folder from Git

git rm --cached -r FolderName

Remove a file from git

git rm --cached SomeFile.ext

And then what?

Now that the files have been removed from the local git cache, you should probably either commit the changes you’ve made, or add an entry to your local .gitignore file and then commit the changes.

Recover a secret string from random triplets in Java

Tue, 19 Jan 2021 00:47:12 +0000

The challenge

There is a secret string which is unknown to you. Given a collection of random triplets from the string, recover the original string.

A triplet here is defined as a sequence of three letters such that each letter occurs somewhere before the next in the given string. “whi” is a triplet for the string “whatisup”.

As a simplification, you may assume that no letter occurs more than once in the secret string.

Range Extraction in Java

Mon, 18 Jan 2021 00:47:00 +0000

The challenge

A format for expressing an ordered list of integers is to use a comma separated list of either

individual integers
or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, ‘-‘. The range includes all integers in the interval including both endpoints. It is not considered a range unless it spans at least 3 numbers. For example “12,13,15-17”

Complete the solution so that it takes a list of integers in increasing order and returns a correctly formatted string in the range format.

Reversed Words in Java

Sun, 17 Jan 2021 00:07:51 +0000

The challenge

Complete the solution so that it reverses all of the words within the string passed in.

Example:

ReverseWords.reverseWords("The greatest victory is that which requires no battle");
// should return "battle no requires which that is victory greatest The"

The solution in Java code

Option 1 (using StringBuilder):

public class ReverseWords{

 public static String reverseWords(String str){
     String[] words = str.split(" ");
   
     StringBuilder sb = new StringBuilder();
     
     for (int i=words.length-1; i>=0; i--) {
         sb.append(words[i]).append(" ");
     }
     
     return sb.toString().trim();
 }

}

Option 2 (using Arrays):

CamelCase Method in Java

Sat, 16 Jan 2021 00:09:40 +0000

The challenge

Write a simple CamelCase method for strings.

All words must have their first letter capitalized without spaces.

Example:

// "HelloCase"
camelCase("hello case");

// "CamelCaseWord"
camelCase("camel case word");

The solution in Java code

Option 1:

public class Solution {

    public static String camelCase(String str) {
        String[] words = str.trim().split("\\s+");
        if (words.length==0) return "";
        StringBuilder sb = new StringBuilder();
      
        for (int i=0; i<words.length; i++) {
            String word = words[i];
            if (word.length()>1) {
              String s = word.substring(0, 1).toUpperCase() + word.substring(1, word.length());
              sb.append(s);
            } else {
              sb.append(word.toUpperCase());
            }
        }
      
        return sb.toString();
    }

}

Option 2:

Even or Odd in Java

Fri, 15 Jan 2021 01:01:00 +0000

The challenge

Create a function that takes an integer as an argument and returns “Even” for even numbers or “Odd” for odd numbers.

The solution in Java code

public class EvenOrOdd {
    public static String even_or_odd(int number) {
        return number%2==0 ? "Even" : "Odd";
    }
}

Test cases to validate our solution

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class EvenOrOddTest {
    @Test
    public void testEvenOrOdd() {
        EvenOrOdd eoo = new EvenOrOdd();
        assertEquals(eoo.even_or_odd(6), "Even");
        assertEquals(eoo.even_or_odd(7), "Odd");       
    }
}

Square Every Digit in Java

Thu, 14 Jan 2021 01:14:00 +0000

The challenge

You need to square every digit of a number and concatenate them.

For example, if we run 9119 through the function, 811181 will come out, because 92 is 81 and 12 is 1.

Note: The function accepts an integer and returns an integer.

The solution in Java code

Option 1:

public class SquareDigit {

  public int squareDigits(int n) {
    String result = ""; 
    
    while (n != 0) {
      int digit = n % 10 ;
      result = digit*digit + result ;
      n /= 10 ;
    }
    
    return Integer.parseInt(result) ;
  }

}

Option 2:

Simple number sequence in Java

Wed, 13 Jan 2021 00:15:21 +0000

The challenge

You are given a string of numbers in sequence and your task will be to return the missing number. If there is no number missing or there is an error in the sequence, return -1.

For example:

missing("123567") = 4 
missing("899091939495") = 92
missing("9899101102") = 100
missing("599600601602") = -1 -- no number missing
missing("8990919395") = -1 -- error in sequence. Both 92 and 94 missing.

The sequence will always be in ascending order.

Roman Numerals Encoder in Java

Tue, 12 Jan 2021 00:40:34 +0000

The challenge

Create a function taking a positive integer as its parameter and returning a string containing the Roman Numeral representation of that integer.

First Variation on Caesar Cipher in Java

Mon, 11 Jan 2021 00:13:27 +0000

The challenge

The action of a Caesar cipher is to replace each plaintext letter (plaintext letters are from ‘a’ to ‘z’ or from ‘A’ to ‘Z’) with a different one a fixed number of places up or down the alphabet.

This program performs a variation of the Caesar shift. The shift increases by 1 for each character (on each iteration).

If the shift is initially 1, the first character of the message to be encoded will be shifted by 1, the second character will be shifted by 2, etc…

Century From Year in Java

Sun, 10 Jan 2021 01:35:27 +0000

The challenge

The first century spans from the year 1 up to and including the year 100, The second – from the year 101 up to and including the year 200, etc.

Task :

Given a year, return the century it is in.

Input, Output Examples

centuryFromYear(1705)  returns (18)
centuryFromYear(1900)  returns (19)
centuryFromYear(1601)  returns (17)
centuryFromYear(2000)  returns (20)

The solution in Java code

Option 1:

public class Solution {
  public static int century(int number) {
    return (number + 99) / 100;
  }
}

Option 2:

Find the Smallest Number in Java

Sat, 09 Jan 2021 01:00:00 +0000

The challenge

You have a positive number n consisting of digits. You can do at most one operation: Choosing the index of a digit in the number, remove this digit at that index and insert it back to another or at the same place in the number in order to find the smallest number you can get.

#Task: Return an array or a tuple or a string depending on the language (see “Sample Tests”) with

Convert Array to Tree in Java

Fri, 08 Jan 2021 00:37:45 +0000

The challenge

You are given a non-null array of integers. Implement the method arrayToTree which creates a binary tree from its values in accordance to their order, while creating nodes by depth from left to right.

For example, given the array [17, 0, -4, 3, 15] you should create the following tree:

The class TreeNode is available for you:

class TreeNode {

    TreeNode left;
    TreeNode right;
    int value;

    TreeNode(int value, TreeNode left, TreeNode right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }

    TreeNode(int value) {
        this(value, null, null);
    }

    @Override
    public boolean equals(Object other) {
        ... // Already implemented for you and used in test cases 
    }
    ...
}

The solution in Java code

Option 1:

Common Denominators in Java

Thu, 07 Jan 2021 00:19:14 +0000

The challenge

You will have a list of rationals in the form

{ {numer_1, denom_1} , ... {numer_n, denom_n} } 
or
[ [numer_1, denom_1] , ... [numer_n, denom_n] ] 
or
[ (numer_1, denom_1) , ... (numer_n, denom_n) ]

where all numbers are positive ints. You have to produce a result in the form:

(N_1, D) ... (N_n, D) 
or
[ [N_1, D] ... [N_n, D] ] 
or
[ (N_1', D) , ... (N_n, D) ] 
or
{{N_1, D} ... {N_n, D}} 
or
"(N_1, D) ... (N_n, D)"

depending on the language (See Example tests)

Primes in Numbers in Java

Wed, 06 Jan 2021 01:19:08 +0000

The challenge

Given a positive number n > 1 find the prime factor decomposition of n. The result will be a string with the following form :

 "(p1**n1)(p2**n2)...(pk**nk)"

where a ** b means a to the power of b

with the p(i) in increasing order and n(i) empty if n(i) is 1.

Example: n = 86240 should return "(2**5)(5)(7**2)(11)"

The solution in Java code

Option 1:

public class PrimeDecomp {

    public static String factors(int lst) {
        String result = "";
        for (int fac = 2; fac <= lst; ++fac) {
            int count;
            for (count = 0; lst % fac == 0; ++count) {
                lst /= fac;
            }
            if (count > 0) {
                result += "(" + fac + (count > 1 ? "**" + count : "") + ")";
            }
        }
        return result;
    }
}

Option 2:

Maximum subarray sum in Java

Tue, 05 Jan 2021 01:28:02 +0000

The challenge

The maximum sum subarray problem consists in finding the maximum sum of a contiguous subsequence in an array or list of integers:

Max.sequence(new int[]{-2, 1, -3, 4, -1, 2, 1, -5, 4});
// should be 6: {4, -1, 2, 1}

Easy case is when the list is made up of only positive numbers and the maximum sum is the sum of the whole array. If the list is made up of only negative numbers, return 0 instead.

Validate Credit Card Number in Java

Mon, 04 Jan 2021 02:28:25 +0000

The challenge

Let’s implement the Luhn Algorithm, which is used to help validate credit card numbers.

Given a positive integer of up to 16 digits, return true if it is a valid credit card number, and false if it is not.

Here is the algorithm:

Double every other digit, scanning from right to left, starting from the second digit (from the right).Another way to think about it is: if there are an even number of digits, double every other digit starting with the first; if there are an odd number of digits, double every other digit starting with the second:1714 ==> [1*, 7, 1*, 4] ==> [2, 7, 2, 4] 12345 ==> [1, 2*, 3, 4*, 5] ==> [1, 4, 3, 8, 5] 891 ==> [8, 9*, 1] ==> [8, 18, 1]
If a resulting number is greater than 9, replace it with the sum of its own digits (which is the same as subtracting 9 from it):[8, 18*, 1] ==> [8, (1+8), 1] ==> [8, 9, 1] or: [8, 18*, 1] ==> [8, (18-9), 1] ==> [8, 9, 1]
Sum all of the final digits:[8, 9, 1] ==> 8 + 9 + 1 = 18
Finally, take that sum and divide it by 10. If the remainder equals zero, the original credit card number is valid. 18 (modulus) 10 ==> 8 , which is not equal to 0, so this is not a valid credit card number

The solution in Java code

Option 1:

Find the unique number using Java

Sun, 03 Jan 2021 00:07:35 +0000

The challenge

There is an array with some numbers. All numbers are equal except for one. Try to find it!

Solution.findUniq(new double[]{ 1, 1, 1, 2, 1, 1 }); // => 2
Solution.findUniq(new double[]{ 0, 0, 0.55, 0, 0 }); // => 0.55

It’s guaranteed that array contains at least 3 numbers.

The tests contain some very huge arrays, so think about performance.

The solution in Java code

Option 1:

import java.util.Arrays;
 public class Solution {
    public static double findUniq(double[] arr) {
      Arrays.sort(arr);
      return arr[0] == arr[1] ? arr[arr.length-1]:arr[0];
    }
}

Option 2:

Find The Parity Outlier in Java

Sat, 02 Jan 2021 01:07:42 +0000

The challenge

You are given an array (which will have a length of at least 3, but could be very large) containing integers. The array is either entirely comprised of odd integers or entirely comprised of even integers except for a single integer N. Write a method that takes the array as an argument and returns this “outlier” N.

Examples

[2, 4, 0, 100, 4, 11, 2602, 36]
Should return: 11 (the only odd number)

[160, 3, 1719, 19, 11, 13, -21]
Should return: 160 (the only even number)

The solution in Java

Option 1:

Find the missing letter using Java

Fri, 01 Jan 2021 01:50:09 +0000

The challenge

Write a method that takes an array of consecutive (increasing) letters as input and that returns the missing letter in the array.

You will always get an valid array. And it will be always exactly one letter be missing. The length of the array will always be at least 2.
The array will always contain letters in only one case.

Example:

[‘a’,‘b’,‘c’,’d’,‘f’] -> ‘e’ [‘O’,‘Q’,‘R’,‘S’] -> ‘P’

["a","b","c","d","f"] -> "e"
["O","Q","R","S"] -> "P"

(Use the English alphabet with 26 letters!)

Determine the order of braces is valid using Java

Thu, 31 Dec 2020 01:42:47 +0000

The challenge

Write a function that takes a string of braces, and determines if the order of the braces is valid. It should return true if the string is valid, and false if it’s invalid.

All input strings will be nonempty, and will only consist of parentheses, brackets and curly braces: ()[]{}.

What is considered Valid?

A string of braces is considered valid if all braces are matched with the correct brace.

[Solved] PKIX path building failed: unable to find valid certification path to requested target

Wed, 30 Dec 2020 02:02:44 +0000

The problem

It may happen to you that when you try and pull some Java dependencies, you will get the annoying PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target error.

It may look something like this:

Could not transfer artifact org.springframework.boot:spring-boot-starter-parent:pom:2.4.0 from/to tpvr-ibm (https://nexus-***.***.***.***:8081/nexus/content/repositories/tpvr-ibm): PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

The solution (recommended)

Go to URL in your browser:
- firefox – click on HTTPS certificate chain (the lock icon right next to URL address). Click "more info" > "security" > "show certificate" > "details" > "export..". Pickup the name and choose file type example.cer
- chrome – click on site icon left to address in address bar, select “Certificate” -> “Details” -> “Export” and save in format “Der-encoded binary, single certificate”.
Now you have file with keystore and you have to add it to your JVM. Determine location of cacerts files
- Windows: C:\Program Files (x86)\Java\jre1.8.0_22\lib\security\cacerts
- Mac: /Library/Java/JavaVirtualMachines/jdk1.8.0_221.jdk/Contents/Home/jre/lib/security/cacerts
Next import the example.cer file into cacerts in command line:

What commands to run

Navigate to the security path:

How to Find the odd int in Java

Tue, 29 Dec 2020 01:19:47 +0000

The challenge

Given an array of integers, find the one that appears an odd number of times.

There will always be only one integer that appears an odd number of times.

The solution in Java code

Option 1 (using streams):

import static java.util.Arrays.stream;

public class FindOdd {
  public static int findIt(int[] arr) {
    return stream(arr).reduce(0, (x, y) -> x ^ y);
  }
}

Option 2 (using xor):

public class FindOdd {
  public static int findIt(int[] A) {
    int odd = 0;
    
    for (int i : A) {
      odd ^= i;
    }
  
    return odd;
  }
}

Option 3 (using a TreeSet):

Count the number of Duplicates in Java

Mon, 28 Dec 2020 01:42:41 +0000

The challenge

Write a function that will return the count of distinct case-insensitive alphabetic characters and numeric digits that occur more than once in the input string. The input string can be assumed to contain only alphabets (both uppercase and lowercase) and numeric digits.

Example

“abcde” -> 0 # no characters repeats more than once
“aabbcde” -> 2 # 'a' and 'b'
“aabBcde” -> 2 # 'a' occurs twice and 'b' twice (`b` and `B`)
“indivisibility” -> 1 # 'i' occurs six times
“Indivisibilities” -> 2 # 'i' occurs seven times and 's' occurs twice
“aA11” -> 2 # 'a' and '1'
“ABBA” -> 2 # 'A' and 'B' each occur twice

Calculating Simple Max Digit Sum in Java

Sun, 27 Dec 2020 00:45:21 +0000

The challenge

In this challenge, you will be given an integer n and your task will be to return the largest integer that is <= n and has the highest digit sum.

For example:

solve(100) = 99. Digit Sum for 99 = 9 + 9 = 18. No other number <= 100 has a higher digit sum.
solve(10) = 9
solve(48) = 48. Note that 39 is also an option, but 48 is larger.

Input range is 0 < n < 1e11

The String Combat Challenge in Java

Sat, 26 Dec 2020 01:08:29 +0000

The challenge

After a long conflict, the rulers of Nek and Glo have decided that a final duel should decide the fate of their countries. Each ruler will select their best knights and send them into battle, one after another. The last standing team will win the crown.

But the knights don’t want to die for nothing, so they ask you, the wise technomagican, to derive which team will win. Can you help them?

Solving Single Word Pig Latin in Java

Fri, 25 Dec 2020 00:20:35 +0000

The challenge

Pig Latin is an English language game where the goal is to hide the meaning of a word from people not aware of the rules.

So, the goal of this challenge is to write a function that encodes a single word string to pig latin.

The rules themselves are rather easy:

The word starts with a vowel(a,e,i,o,u) -> return the original string plus “way”.
The word starts with a consonant -> move consonants from the beginning of the word to the end of the word until the first vowel, then return it plus “ay”.

Count the Days in Java

Thu, 24 Dec 2020 00:54:51 +0000

The challenge

Little Annie is very excited for upcoming events. She want’s to know how many days she have to wait for a specific event.

Your job is to help her out.

Task: Write a function which returns the number of days from today till the given date. The function will take a Date object as parameter. You have to round the amount of days.

If the event is in the past, return “The day is in the past!”
If the event is today, return “Today is the day!”
Else, return “x days”

Java HashMap Create or Increment Value

Wed, 23 Dec 2020 01:30:00 +0000

If you are using a HashMap to keep a running total of a series of elements, then you often need to increment a HashMap item, but if it doesn’t exist in the map yet, then you need to rather create it.

There are a number of ways to do this, let’s explore some of these.

Using Merge and Sum in Java 8

My absolute favourite is to use Java 8’s ability to do the below:

Get the Strongest even number in an interval in Java

Tue, 22 Dec 2020 02:02:27 +0000

The challenge

A strongness of an even number is the number of times we can successively divide by 2 until we reach an odd number starting with an even number n.

For example, if n = 12, then

12 / 2 = 6
6 / 2 = 3

So we divided successively 2 times and we reached 3, so the strongness of 12 is 2.

If n = 16 then

What time is it? in Java

Mon, 21 Dec 2020 02:00:00 +0000

The challenge

How many times have we been asked this simple question in our daily lives by family, friends and strangers alike?

In this challenge you take a look at your watch and answer this question in proper English. Sometimes you have your watch in 24h format and others in 12h. The AM/PM part of the time is always disregarded as the asker knows whether it’s morning or afternoon.

Requirements:

Mind the punctuation for the full hours; o’clock is written as one word.
Spacing between individual words is strictly limited to one space. Cardinal numbers greater than 20 are hyphenated (e.g. “twenty-one”).
Input is always going to be a non-null string in the format \d{2}:\d{2}(\s?[ap]m)?
Both 12h and 24h input may be present. In case of 12h input disregard the am/pm part.
Remember that in 24h midnight is denoted as 00:00.
There may or may not be a space between the minutes and the am/pm part in 12h format.

Examples:

toHumanTime("05:28 pm"); // twenty-eight minutes past five
toHumanTime("12:00");    // twelve o'clock
toHumanTime("03:45am");  // quarter to four
toHumanTime("07:15");    // quarter past seven
toHumanTime("23:30");    // half past eleven
toHumanTime("00:01");    // one minute past twelve
toHumanTime("17:51");    // nine minutes to six

The solution in Java code

Option 1:

Building a String Pyramid in Java

Sun, 20 Dec 2020 02:00:00 +0000

The challenge

You have to build a pyramid.

This pyramid should be built from characters from a given string.

You have to create the code for these four methods:

public static String watchPyramidFromTheSide(String characters)

public static String watchPyramidFromAbove(String characters)

public static int countVisibleCharactersOfThePyramid(String characters)

public static int countAllCharactersOfThePyramid(String characters)

The first method (“FromTheSide”) shows the pyramid as you would see from the side.
The second method (“FromAbove”) shows the pyramid as you would see from above.
The third method (“CountVisibleCharacters”) should return the count of all characters, that are visible from outside the pyramid.
The forth method (“CountAllCharacters”) should count all characters of the pyramid. Consider that the pyramid is completely solid and has no holes or rooms in it.

Cartesian coordinates from degree angle in Java

Sat, 19 Dec 2020 02:00:00 +0000

The challenge

Write a simple function that takes polar coordinates (an angle in degrees and a radius) and returns the equivalent cartesian coordinates (rounded to 10 places).

For example:

coordinates(90,1) => (0.0, 1.0)

coordinates(45, 1) => (0.7071067812, 0.7071067812)

The solution in Java code

Option 1:

import java.awt.geom.Point2D;

class CoordinatesInspector {
  Point2D.Double coordinates(Double degrees, Double radius) {
    return new Point2D.Double(
        Math.round(radius * Math.cos(Math.toRadians(degrees)) * 10e9) / 10e9,
        Math.round(radius * Math.sin(Math.toRadians(degrees)) * 10e9) / 10e9);
  }
}

Option 2:

Sort array by sorting its smallest sub-array in Java

Fri, 18 Dec 2020 02:08:41 +0000

The challenge

Given an array of integers, arr, find out 2 indices m, n(0<=m<=arr.length-1, 0<=n<=arr.length-1, m<=n), so that as long as all elements in the subarray(from index m to n, indices m and n inclusive) are sorted properly, with this sorted subarray relacing original subarray, the whole array is sorted (no matter ascendingly or descendingly).

The subarray should include the least number of elements, means (n-m) must be of the smallest value, and n should also be the smallest one.

Excessively Abundant Numbers in Java

Thu, 17 Dec 2020 02:00:00 +0000

The challenge

An abundant number or excessive number is a number for which the sum of its proper divisors is greater than the number itself.

The integer 12 is the first abundant number. Its proper divisors are 1, 2, 3, 4 and 6 for a total of 16 (> 12).

Derive function abundantNumber(num)/abundant_number(num) which returns true/True/.true. if num is abundant, false/False/.false. if not.

The solution in Java code

Option 1 (using IntStream):

Unique Substring From Joined Strings in Java

Wed, 16 Dec 2020 02:59:47 +0000

The challenge

Write a function that takes two strings, A and B, and returns the length of the longest possible substring that can be formed from the concatenation of either A + B or B + A containing only characters that do not appear in both A and B.

Example:

Given the strings “piquancy” and “refocusing”:
A = “piquancy”
B = “refocusing”
A + B = “piquancyrefocusing”
B + A = “refocusingpiquancy”

Converting from Base 10 to 16 (Decimal to Hex) in Java

Tue, 15 Dec 2020 00:04:38 +0000

The challenge

Convert an integer which is base 10, to a hexadecimal base 16 string.

Java provides various built-in options such as Integer.toString(a, 16), or String.format("0x%X", a), or Integer.toHexString(a)

The solution in Java code

Option 1:

public class Hexadecimal{
    public static String convertToHex(int a){
        return "0x"+Integer.toHexString(a).toUpperCase();
    }
}

Option 2:

public class Hexadecimal{

private static final String hexDigits = "0123456789ABCDEF";
    public static String convertToHex(int a) {
        String hexadecimal = "";

        while (a > 0) {
            int digit = a % 16;
            hexadecimal = hexDigits.charAt(digit) + hexadecimal;
            a = a / 16;
        }
        return "0x" + hexadecimal;
    }
}

Option 3:

How to Format Numbers by Prepending 0 to single-digit numbers in Javascript

Mon, 14 Dec 2020 01:40:53 +0000

If you have a single-digit number, and you need to format it to always have at-least two digits, then you can use the below function to solve your problem:

function toAtleastTwoPlaces(n){
    return n > 9 ? "" + n: "0" + n;
}

When testing the above method, you could do the following:

toAtleastTwoPlaces(9);   //Returns "09"
toAtleastTwoPlaces(10);  //Returns "10"
toAtleastTwoPlaces(999); //Returns "999"

This is especially useful where you need to format dates:

String polynomial converter in Java

Sun, 13 Dec 2020 01:29:23 +0000

The challenge

Your task is to programe:

String convertToString(int[] pol) {....} The method returns given by a parameter, (integer array) which represents a polynomial, the representation of the polynomial in String format. NOTE:

array{a, b, c, d, e,...., z}
      0  1  2  3  4 ....  n

The numbers indicate the grade of the polynomial, where n is a positive integer always. Some examples:

array{0,1,-2,0,5}  -> convertToString(array) -> "5x^4-2x^2+x"
array{1,1,-2,0,0}  -> convertToString(array) -> "-2x^2+x+1"
array{}  -> convertToString(array) -> ""
array{0,0,7,0,0}  -> convertToString(array) -> "7x^2"
array{1,0,0,0,0}  -> convertToString(array) -> "1"
array{0,1,-1,0,5,0,0,1}  -> convertToString(array) -> "x^7+5x^4-x^2+x"

The solution in Java code

Option 1:

How to Remove all Exclamation Marks from a String in Java

Sat, 12 Dec 2020 02:00:00 +0000

The challenge

Write function RemoveExclamationMarks which removes all exclamation marks from a given string.

The solution in Java code

Option 1:

class Solution {
    static String removeExclamationMarks(String s) {
        return s.replaceAll("!", "");
    }
}

Option 2:

class Solution {
    static String removeExclamationMarks(String s) {
        return s.replace("!", "");
    }
}

Test cases to validate our solution in Java

import org.junit.Test;
import java.util.Random;
import java.util.stream.*;
import static org.junit.Assert.assertEquals;

public class SolutionTest {

    @Test
    public void testSimpleString1() {
        assertEquals("Hello World", Solution.removeExclamationMarks("Hello World!"));
    }
    
    @Test
    public void testSimpleString2() {
        assertEquals("Hello World", Solution.removeExclamationMarks("Hello World!!!"));
    }
    
    @Test
    public void testSimpleString3() {
        assertEquals("Hi Hello", Solution.removeExclamationMarks("Hi! Hello!"));
    }
    
    @Test
    public void testRandomString() {
        String rs = String.format("%s!%s %s!%s", randomString(), randomString(), randomString(), randomString());
        assertEquals(solution(rs), Solution.removeExclamationMarks(rs));
    }
    
    private String randomString() {
        Random random = new Random();
        String abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZbcdefghijklmnopqrstuvwxyz";
        return IntStream.range(0, 10)
                        .mapToObj(__ -> (char) abc.charAt(random.nextInt(abc.length())))
                        .map(String::valueOf)
                        .collect(Collectors.joining(""));
    }
    
    private String solution(String s) {
        return s.replaceAll("!", "");
    }
}

How to Convert a Number to a String in Java

Fri, 11 Dec 2020 03:52:07 +0000

The challenge

We need a function that can transform a number into a string.

What ways of achieving this do you know?

Examples:

Solution.numberToString(123); // returns "123";   
Solution.numberToString(999); // returns "999";

The solution in Java code

The easiest way to do this is to use the String.valueOf method to take an integer and return a string:

class Solution {
  public static String numberToString(int num) {
    return String.valueOf(num);
  }
}

This can also be done the other way around, using the Integer.toString method:

How to Remove Spaces in a String in Java

Thu, 10 Dec 2020 01:00:23 +0000

The challenge

Simple, remove the spaces from the string, then return the resultant string.

The solution in Java code

class Solution {
    static String noSpace(final String x) {
        return x.replace(" ", "");
    }
}

An alternative:

class Solution {
    static String noSpace(final String x) {
        return x.replaceAll("\\s+","");
    }
}

Test cases to validate our Java solution

import org.junit.Test;
import java.util.Random;
import static org.junit.Assert.assertEquals;

public class SolutionTest {
    @Test public void testSomething() {
        assertEquals("8j8mBliB8gimjB8B8jlB", Solution.noSpace("8 j 8   mBliB8g  imjB8B8  jl  B"));
        assertEquals("88Bifk8hB8BB8BBBB888chl8BhBfd", Solution.noSpace("8 8 Bi fk8h B 8 BB8B B B  B888 c hl8 BhB fd"));
        assertEquals("8aaaaaddddr", Solution.noSpace("8aaaaa dddd r     "));
        assertEquals("jfBmgklf8hg88lbe8", Solution.noSpace("jfBm  gk lf8hg  88lbe8 "));
        assertEquals("8jaam", Solution.noSpace("8j aam"));
    }
    
    private static final String chars = "abc defg hij klm no pq rstuvw xyz";

    @Test public void randomTests() {
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 20; i++) {
            int length = random.nextInt(15) + 1;
            for (int j = 0; j < length; j++) {
                int index = random.nextInt(chars.length());
                sb.append(chars.charAt(index));
            }
            String input = sb.toString();
            sb.setLength(0);
            assertEquals(input.replaceAll(" ", ""), Solution.noSpace(input));
        }
    }
}

How many stairs will Suzuki climb in 20 years? in Java

Wed, 09 Dec 2020 01:49:03 +0000

The challenge

Suzuki is a monk who climbs a large staircase to the monastery as part of a ritual. Some days he climbs more stairs than others depending on the number of students he must train in the morning. He is curious how many stairs might be climbed over the next 20 years and has spent a year marking down his daily progress.

The sum of all the stairs logged in a year will be used for estimating the number he might climb in 20.

Determine if N is divisible by X and Y in Java

Tue, 08 Dec 2020 00:51:34 +0000

The challenge

Create a function that checks if a number n is divisible by two numbers x AND y. All inputs are positive, non-zero digits.

Examples

1) n =   3, x = 1, y = 3 =>  true because   3 is divisible by 1 and 3
2) n =  12, x = 2, y = 6 =>  true because  12 is divisible by 2 and 6
3) n = 100, x = 5, y = 3 => false because 100 is not divisible by 3
4) n =  12, x = 7, y = 5 => false because  12 is neither divisible by 7 nor 5

The solution in Java code

Option 1:

How to Sum a Mixed Array in Java

Mon, 07 Dec 2020 01:40:11 +0000

The challenge

Given an array of integers as strings and numbers, return the sum of the array values as if all were numbers.

Return your answer as a number.

The solution in Java code

Option 1 (using stream):

import java.util.List;

public class MixedSum {

  public int sum(List<?> mixed) {
    return mixed.stream().mapToInt(o -> Integer.parseInt(o.toString())).sum();
  }

}

Option 2 (the harder way):

import java.util.List;

public class MixedSum {
  public int sum(List<?> mixed) { 
      int sum = 0;
    
      for (Object element : mixed) {
        if (element instanceof Integer) {
          sum += (Integer) element;
        } else if (element instanceof String) {
          sum += Integer.parseInt( (String) element );
        }
      }
      return sum;
  }
}

Option 3 (using Objects):

Calculate the Volume of a Cuboid in Java

Sun, 06 Dec 2020 09:45:07 +0000

A Cuboid is a geometric object that is more or less cubic in shape. It is a solid which has six rectangular faces at right angles to each other.

The formula to calculate a cuboid is pretty simple, just multiple the length by the width by the height to get the total volume. We want to calculate volume of cuboid.

Additionally, the volume of cuboid test case below validates the Java code solution.

Find the first non-consecutive number in Java

Sat, 05 Dec 2020 01:24:29 +0000

The challenge

Your task is to find the first element of an array that is not consecutive.

By not consecutive we mean not exactly 1 larger than the previous element of the array.

E.g. If we have an array [1,2,3,4,6,7,8] then 1 then 2 then 3 then 4 are all consecutive but 6 is not, so that’s the first non-consecutive number.

If the whole array is consecutive then return null.

Alternating String Casing in Java

Fri, 04 Dec 2020 00:43:36 +0000

The challenge

altERnaTIng cAsE <=> ALTerNAtiNG CaSe

Define String.prototype.toAlternatingCase (or a similar function/method such as to_alternating_case/toAlternatingCase/ToAlternatingCase in your selected language; see the initial solution for details) such that each lowercase letter becomes uppercase and each uppercase letter becomes lowercase. For example:

StringUtils.toAlternativeString("hello world") == "HELLO WORLD"
StringUtils.toAlternativeString("HELLO WORLD") == "hello world"
StringUtils.toAlternativeString("hello WORLD") == "HELLO world"
StringUtils.toAlternativeString("HeLLo WoRLD") == "hEllO wOrld"
StringUtils.toAlternativeString("12345") == "12345" // Non-alphabetical characters are unaffected
StringUtils.toAlternativeString("1a2b3c4d5e") == "1A2B3C4D5E"
StringUtils.toAlternativeString("StringUtils.toAlternatingCase") == "sTRINGuTILS.TOaLTERNATINGcASE"

As usual, your function/method should be pure, i.e. it should not mutate the original string.

Solving the Pythagorean Triple in Java

Thu, 03 Dec 2020 01:37:57 +0000

The challenge

Given an array of 3 integers a, b and c, determine if they form a pythagorean triple.

A pythagorean triple is formed when:

c2 = a2 + b2

where c is the largest value of a, b, c.

For example: a = 3, b = 4, c = 5 forms a pythagorean triple, because 52 = 32 + 42

How to Correct the Mistakes of the Character Recognition Software in Java

Wed, 02 Dec 2020 00:18:30 +0000

The challenge

Character recognition software is widely used to digitise printed texts. Thus the texts can be edited, searched and stored on a computer.

When documents (especially pretty old ones written with a typewriter), are digitised character recognition softwares often make mistakes.

Your task is correct the errors in the digitised text. You only have to handle the following mistakes:

S is misinterpreted as 5
O is misinterpreted as ``
I is misinterpreted as 1

The test cases contain numbers only by mistake.

Solving “Duck Duck Goose” in Java

Tue, 01 Dec 2020 01:28:38 +0000

The challenge

The objective of Duck, duck, goose is to walk in a circle, tapping on each player’s head until one is chosen.

Task: Given an array of Player objects (an array of associative arrays in PHP) and an index (1-based), return the name of the chosen Player(name is a property of Player objects, e.g Player.name)

Example:

duck_duck_goose([a, b, c, d], 1) should return a.name
duck_duck_goose([a, b, c, d], 5) should return a.name
duck_duck_goose([a, b, c, d], 4) should return d.name

The solution in Java code

Option 1 (returning the modulo):

Calculate averages from an int array in Java

Mon, 30 Nov 2020 00:52:16 +0000

The challenge

Write function avg which calculates average of numbers in given list.

The solution in Java code

Option 1 (working through the problem):

public class Solution {
  public static double find_average(int[] array){
    double sum = 0;
    
    for(int i=0; i<array.length; i++) {
      sum+=array[i];
    }
    
    return sum/array.length;
  }
}

Option 2 (using streams):

import java.util.Arrays;
public class Solution {
  public static double find_average(int[] array){
    return Arrays.stream(array).average().orElse(0);
  }
}

Option 3 (using an IntStream):

How to Rotate a String in Java

Sun, 29 Nov 2020 00:59:10 +0000

Rotating a String in Java is a common interview question, and albeit it quite a simple one, it tests many fundamental concepts. Did I mention that it can also be done fairly quickly too!

Rotating a String in Java

public class Rotater {

    public static void main(String...args) {

        Rotater r = new Rotater();

        System.out.println(r.rotateLeft("test", 1));
        System.out.println(r.rotateRight("test", 1));

    }

    private String rotateLeft(String value, int n) {
        return value.substring(n) + value.substring(0, n);
    }

    private String rotateRight(String value, int n) {
        return rotateLeft(value, value.length() - n);
    }

}

With the above code, we can rotate a string both left and right, but we don’t take into account any edge cases, exception handling, input validation or out of bounds problems.

Calculate the Sum without highest and lowest number in Java

Sat, 28 Nov 2020 00:17:50 +0000

The challenge

Sum all the numbers of the array except the highest and the lowest element (the value, not the index!).
(The highest/lowest element is respectively only one element at each edge, even if there are more than one with the same value!)

Example:

{ 6, 2, 1, 8, 10 } => 16
{ 1, 1, 11, 2, 3 } => 6

If array is empty, null or None, or if only 1 Element exists, return 0.

How to Convert a String to an Array in Java

Fri, 27 Nov 2020 04:04:15 +0000

Java makes it easy to convert a string to an array by providing the built-in .split() method on the String object.

The challenge

Write a function to split a string and convert it into an array of words. For example:

"Robin Singh" ==> ["Robin", "Singh"]

"I love arrays they are my favorite" ==> ["I", "love", "arrays", "they", "are", "my", "favorite"]

The solution in Java code

This is a really simple one, you just split the string with the space character:

How to Loop and Combine Three Strings in Java

Thu, 26 Nov 2020 00:20:56 +0000

The challenge

Create a function that will return a string that combines all of the letters of the three inputed strings in groups. Taking the first letter of all of the inputs and grouping them next to each other. Do this for every letter, see example below!

E.g. Input: “aa”, “bb” , “cc” => Output: “abcabc”

Note: You can expect all of the inputs to be the same length.

The solution in Java code

Option 1:

How to Localize The Barycenter of a Triangle in Java

Wed, 25 Nov 2020 01:40:47 +0000

The challenge

The medians of a triangle are the segments that unit the vertices with the midpoint of their opposite sides. The three medians of a triangle intersect at the same point, called the barycenter or the centroid. Given a triangle, defined by the cartesian coordinates of its vertices we need to localize its barycenter or centroid.

The function bar_triang() or barTriang or bar-triang, receives the coordinates of the three vertices A, B and C as three different arguments and outputs the coordinates of the barycenter O in an array [xO, yO]

How to Calculate a Valid Square in Java

Tue, 24 Nov 2020 00:03:24 +0000

The challenge

Given the coordinates of four points in 2D space p1, p2, p3 and p4, return true if the four points construct a square.

The coordinate of a point pi is represented as [xi, yi]. The input is not given in any order.

A valid square has four equal sides with positive length and four equal angles (90-degree angles).

Example 1:

Example 2:

How to Calculate Age Range Compatibility as an Equation in Java

Mon, 23 Nov 2020 00:58:10 +0000

The challenge

Everybody knows the classic “half your age plus seven” dating rule that a lot of people follow (including myself). It’s the ‘recommended’ age range in which to date someone.

minimum age <= your age <= maximum age

Given an integer (1 <= n <= 100) representing a person’s age, return their minimum and maximum age range.

This equation doesn’t work when the age <= 14, so use this equation instead:

How to Find the Longest Mountain in Array in Java

Sun, 22 Nov 2020 02:41:47 +0000

The challenge

Let’s call any (contiguous) subarray B (of A) a mountain if the following properties hold:

B.length >= 3
There exists some 0 < i < B.length - 1 such that B[0] < B[1] < ... B[i-1] < B[i] > B[i+1] > ... > B[B.length - 1]

(Note that B could be any subarray of A, including the entire array A.)

Given an array A of integers, return the length of the longest mountain.

How to tell what the CHMOD value of a file/directory is

Sat, 21 Nov 2020 00:57:59 +0000

chmod alters the permissions for a file or directory, you could allow full read/write access to a file or directory by running the following command:

chmod 777 myfile.ext

You could do the same on a directory recursively:

chmod -R 777 mydirectory

But if we look at the directory listing of this path now, we can’t tell what integer value this affected:

$ ls -lash

0 -rwxrwxrwx   1 ao  staff     0B 18 Nov 13:29 myfile.ext

How to get the CHMOD value

If we want to get the actual integer value back, we could use the stat command and tell it what we want from it:

How to Solve the “Decode a String” Challenge in Java

Fri, 20 Nov 2020 01:42:32 +0000

The challenge

Given an encoded string, return its decoded string.

The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer.

You may assume that the input string is always valid; No extra white spaces, square brackets are well-formed, etc.

Furthermore, you may assume that the original data does not contain any digits and that digits are only for those repeat numbers, k. For example, there won’t be input like 3a or 2[4].

How to cleanup a /var/log/journal in Linux

Thu, 19 Nov 2020 00:06:48 +0000

You may find your /var/log/journal directory taking up a lot of disk-space.

How do you go about removing, or deleting all these files under var log journal without the system complaining and falling over?

How to tell how much space is being taken?

You can ask the journalctl command directly, using the --disk-usage argument:

journalctl --disk-usage

It will report something like this:

Journals take up 3.9G on disk.

Fix: Option 1 (not ideal):

Go and adjust its config under /etc/systemd/journald.conf, making sure to pay attention to the SystemMaxUse key; set this to something reasonable, like 50M perhaps.

How to Find the Maximum Difference Between Node and Ancestor in Java

Wed, 18 Nov 2020 00:43:35 +0000

The challenge

Given the root of a binary tree, find the maximum value V for which there exist different nodes A and B where V = |A.val - B.val| and A is an ancestor of B.

A node A is an ancestor of B if either: any child of A is equal to B, or any child of A is an ancestor of B.

Example 1:

Example 2:

How to Find the Integral using Java

Tue, 17 Nov 2020 01:43:39 +0000

The challenge

Create a function that finds the integral of the expression passed.

In order to find the integral all you need to do is add one to the exponent (the second argument), and divide the coefficient (the first argument) by that new number.

For example for 3x^2, the integral would be 1x^3: we added 1 to the exponent, and divided the coefficient by that new number).

How to Build Strings from a Size in Java

Mon, 16 Nov 2020 01:18:54 +0000

The challenge

Write a function stringy that takes a size and returns a string of alternating '1s' and '0s'.

The string should start with a 1.

A string with size 6 should return :'101010'.

With size 4 should return : '1010'.

With size 12 should return : '101010101010'.

The size will always be positive and will only use whole numbers.

The solution in Java code

public class Solution {
  public static String stringy(int size) {
    int last = 1;
    StringBuilder sb = new StringBuilder();
    
    for (int i=0; i<size; i++) {
      sb.append(last);
      last = last==0 ? 1 : 0;
    }
    
    return sb.toString();
  }
}

We could make this a little simpler by doing the following:

Best Time to Buy and Sell Stock in Java

Sun, 15 Nov 2020 01:59:41 +0000

The challenge

Say you have an array for which the ith element is the price of a given stock on day i.

If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Note that you cannot sell a stock before you buy one.

How to Solve the “To square(root) or not to square(root)” Challenge in Java

Sat, 14 Nov 2020 00:43:00 +0000

The challenge

Write a method, that will get an integer array as parameter and will process every number from this array.
Return a new array with processing every number of the input-array like this:

If the number has an integer square root, take this, otherwise square the number.

[4,3,9,7,2,1] -> [2,9,3,49,4,1]

The input array will always contain only positive numbers and will never be empty or null.

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.Arrays;

public class SolutionTest {
    @Test
    public void basicTests() {
        int[] input = new int[] { 4, 3, 9, 7, 2, 1 };
        int[] expected = new int[] { 2, 9, 3, 49, 4, 1 };
        assertEquals(Arrays.toString(expected), Arrays.toString(Squarer.squareOrSquareRoot(input)));

        input = new int[] { 100, 101, 5, 5, 1, 1 };
        expected = new int[] { 10, 10201, 25, 25, 1, 1 };
        assertEquals(Arrays.toString(expected), Arrays.toString(Squarer.squareOrSquareRoot(input)));

        input = new int[] { 1, 2, 3, 4, 5, 6 };
        expected = new int[] { 1, 4, 9, 2, 25, 36 };
        assertEquals(Arrays.toString(expected), Arrays.toString(Squarer.squareOrSquareRoot(input)));        
    }
}

The solution in Java

Option 1 (using a loop):

Solving the Rule of Divisibility by 13 in Java

Fri, 13 Nov 2020 02:01:03 +0000

The challenge

wikipedia.com

When you divide the successive powers of 10 by 13 you get the following remainders of the integer divisions:

1, 10, 9, 12, 3, 4 because:

(For “mod” you can see: https://en.wikipedia.org/wiki/Modulo_operation)

Then the whole pattern repeats. Hence the following method:

How to Calculate Buddy Strings in Java

Thu, 12 Nov 2020 00:39:23 +0000

The challenge

Given two strings A and B of lowercase letters, return true if you can swap two letters in A so the result is equal to B, otherwise, return false.

Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at A[i] and A[j]. For example, swapping at indices `` and 2 in "abcd" results in "cbad".

Example 1:

How to Flip a Binary Matrix in Java

Wed, 11 Nov 2020 00:44:27 +0000

The challenge

Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image.

To flip an image horizontally means that each row of the image is reversed. For example, flipping [1, 1, 0] horizontally results in [0, 1, 1].

To invert an image means that each  is replaced by `1`, and each `1` is replaced by . For example, inverting [0, 1, 1] results in [1, 0, 0].

How to Tilt a Binary Tree in Java

Tue, 10 Nov 2020 00:59:43 +0000

The challenge

Given the root of a binary tree, return the sum of every tree node’s tilt.

The tilt of a tree node is the absolute difference between the sum of all left subtree node values and all right subtree node values. If a node does not have a left child, then the sum of the left subtree node values is treated as ``. The rule is similar if there the node does not have a right child.

How to solve the House Robber Challenge in Java

Mon, 09 Nov 2020 00:47:14 +0000

The challenge

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

How to Solve the Bag of Tokens Challenge in Java

Sun, 08 Nov 2020 02:37:30 +0000

The challenge

You have an initial power of P, an initial score of ``, and a bag of tokens where tokens[i] is the value of the ith token (0-indexed).

Your goal is to maximize your total score by potentially playing each token in one of two ways:

If your current power is at least tokens[i], you may play the ith token face up, losing tokens[i] power and gaining 1 score.
If your current score is at least 1, you may play the ith token face down, gaining tokens[i] power and losing 1 score.

Each token may be played at most once and in any order. You do not have to play all the tokens.

How to Find the Smallest Divisor Given a Threshold in Java

Sat, 07 Nov 2020 00:59:43 +0000

The challenge

Given an array of integers nums and an integer threshold, we will choose a positive integer divisor and divide all the array by it and sum the result of the division. Find the smallest divisor such that the result mentioned above is less than or equal to threshold.

Each result of division is rounded to the nearest integer greater than or equal to that element. (For example: 7/3 = 3 and 10/2 = 5).

How to Sort and Star a String Array in Java

Fri, 06 Nov 2020 00:48:18 +0000

The challenge

You will be given a vector of strings. You must sort it alphabetically (case-sensitive, and based on the ASCII values of the chars) and then return the first value.

The returned value must be a string, and have "***" between each of its letters.

You should not remove or add elements from/to the array.

The solution in Java code

At first we could approach the problem by using the built-in Arrays.sort() method and then looping through the first string, placing asterisks inbetween each letter:

How to Count Consecutive Characters in Java

Thu, 05 Nov 2020 09:20:13 +0000

The challenge

Given a string s, the power of the string is the maximum length of a non-empty substring that contains only one unique character.

Return the power of the string.

Example 1:

Example 2:

Example 3:

Example 4:

Example 5:

How to Abbreviate a Two Word Name in Java

Wed, 04 Nov 2020 02:26:24 +0000

The challenge

Write a function to convert a name into initials. This challenge strictly takes two words with one space in between them.

The output should be two capital letters with a dot separating them.

It should look like this:

Sam Harris => S.H

Patrick Feeney => P.F

The solution in Java

This is a really easy one, basically what we will do is the following:

Convert our name toUpperCase so that we can just pull out the characters we want.
Convert the name String into 2 separate values, stored in a names array.
Return the first character of each, using charAt(0) with a dot inbetween.

public class AbbreviateTwoWords {

  public static String abbrevName(String name) {
    name = name.toUpperCase();
    
    String[] names = name.split(" ");
    
    return names[0].charAt(0)+"."+names[1].charAt(0);
  }
}

Test cases to validate our solutionn

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
 
    @Test
    public void testFixed() {
        assertEquals("S.H", AbbreviateTwoWords.abbrevName("Sam Harris"));
        assertEquals("P.F", AbbreviateTwoWords.abbrevName("Patrick Feenan"));
        assertEquals("E.C", AbbreviateTwoWords.abbrevName("Evan Cole"));
        assertEquals("P.F", AbbreviateTwoWords.abbrevName("P Favuzzi"));
        assertEquals("D.M", AbbreviateTwoWords.abbrevName("David Mendieta"));
        assertEquals("Z.K", AbbreviateTwoWords.abbrevName("Zenon Kapusta"));
        
        assertEquals("G.C", AbbreviateTwoWords.abbrevName("george clooney"));
        assertEquals("M.M", AbbreviateTwoWords.abbrevName("marky mark"));
        assertEquals("E.D", AbbreviateTwoWords.abbrevName("eliza doolittle"));
        assertEquals("R.W", AbbreviateTwoWords.abbrevName("reese witherspoon"));
    }
    
    @Test
    public void testRandom() {
      for(int i = 0; i < 200; i++){
        String testString = makeString();
        assertEquals(randomTest(testString), AbbreviateTwoWords.abbrevName(testString));
      }
    }
    
    private String makeString() {
        return makeWord(1, 20) + " " + makeWord(1, 20);
      }
    
    private String makeWord(int min, int max) {
      String word = "";
      String[] possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".split("");
      int length = (int) (Math.random() * max) + min;
    
      for(int i=0; i < length; i++) {
          int index = (int) (Math.random() * possible.length);
          word += possible[index];
      }
    
      return word;
    }
    
    private String randomTest(String name){
      String[] nameSplit = name.toUpperCase().split(" ");
      return nameSplit[0].substring(0, 1) + '.' + nameSplit[1].substring(0, 1);
    }
}

How to Sort a Linked List using Insertion Sort in Java

Tue, 03 Nov 2020 01:21:06 +0000

The challenge

Sort a linked list using insertion sort.

A graphical example of insertion sort. The partially sorted list (black) initially contains only the first element in the list.With each iteration, one element (red) is removed from the input data and inserted in-place into the sorted list

Algorithm of Insertion Sort:

Insertion sort iterates, consuming one input element each repetition, and growing a sorted output list.
At each iteration, insertion sort removes one element from the input data, finds the location it belongs within the sorted list, and inserts it there.
It repeats until no input elements remain.

Example 1:

How to Remove First and Last Character in a String in Java

Mon, 02 Nov 2020 02:21:09 +0000

The challenge

The goal is to create a function that removes the first and last characters of a string. You don’t have to worry with strings with less than two characters.

The solution in Java code

public class RemoveChars {
    public static String remove(String str) {
        return str.substring(1, str.length()-1);
    }
}

Test cases to validate our Java solution

import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class RemoveCharsTest {

    @Test
    public void testRemoval() {
        assertEquals("loquen", RemoveChars.remove("eloquent"));
        assertEquals("ountr", RemoveChars.remove("country"));
        assertEquals("erso", RemoveChars.remove("person"));
        assertEquals("lac", RemoveChars.remove("place"));
    }
}

How to Distribute Halloween Candies by Rating Value in Java

Sun, 01 Nov 2020 02:38:29 +0000

The challenge

There are N children standing in a line. Each child is assigned a rating value.

You are giving candies to these children subjected to the following requirements:

Each child must have at least one candy.
Children with a higher rating get more candies than their neighbors.

What is the minimum candies you must give?

Example 1:

Example 2:

How to Distribute Halloween Candies in Java

Sat, 31 Oct 2020 00:11:01 +0000

The challenge

You have n candies, the ith candy is of type candies[i].

You want to distribute the candies equally between a sister and a brother so that each of them gets n / 2 candies (n is even). The sister loves to collect different types of candies, so you want to give her the maximum number of different types of candies.

Return the maximum number of different types of candies you can give to the sister.

How to Solve the Maximize Distance to Closest Person Challenge in Java

Fri, 30 Oct 2020 00:25:39 +0000

The challenge

You are given an array representing a row of seats where seats[i] = 1 represents a person sitting in the ith seat, and seats[i] = 0 represents that the ith seat is empty (0-indexed).

There is at least one empty seat, and at least one person sitting.

Alex wants to sit in the seat such that the distance between him and the closest person to him is maximized.

How to Get Character from ASCII Value in Java

Thu, 29 Oct 2020 01:01:29 +0000

The challenge

Write a function which takes a number and returns the corresponding ASCII char for that value.

Example:

Ascii.getChar(65) // => 'A'

For ASCII table, you can refer to http://www.asciitable.com/

The solution in Java

public class Ascii {
  public static char getChar(int c) {
    return (char) c;
  }
}

Test cases to validate our solution

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void testChar() {
        assertEquals('7', Ascii.getChar(55));
        assertEquals('8', Ascii.getChar(56));
        assertEquals('9', Ascii.getChar(57));
        assertEquals(':', Ascii.getChar(58));
        assertEquals(';', Ascii.getChar(59));
        assertEquals('<', Ascii.getChar(60));
        assertEquals('=', Ascii.getChar(61));
        assertEquals('>', Ascii.getChar(62));
        assertEquals('?', Ascii.getChar(63));
        assertEquals('@', Ascii.getChar(64));
        assertEquals('A', Ascii.getChar(65));
        assertEquals("getChar should return a `char`", 0, Character.compare('!', Ascii.getChar(33)));
    }
}

Finding a Needle in a Haystack in Java

Wed, 28 Oct 2020 01:50:17 +0000

The challenge

Can you find the needle in the haystack?

Write a function findNeedle() that takes an array full of junk but containing one "needle"

After your function finds the needle it should return a message (as a string) that says:

"found the needle at position " plus the index it found the needle, so:

findNeedle(new Object[] {"hay", "junk", "hay", "hay", "moreJunk", "needle", "randomJunk"})

should return "found the needle at position 5"

How to Solve the Champagne Tower in Java

Tue, 27 Oct 2020 00:45:45 +0000

The challenge

We stack glasses in a pyramid, where the first row has 1 glass, the second row has 2 glasses, and so on until the 100th row. Each glass holds one cup (250ml) of champagne.

Then, some champagne is poured in the first glass at the top. When the topmost glass is full, any excess liquid poured will fall equally to the glass immediately to the left and right of it. When those glasses become full, any excess champagne will fall equally to the left and right of those glasses, and so on. (A glass at the bottom row has its excess champagne fall on the floor.)

How to Solve the 132 Pattern in Java

Mon, 26 Oct 2020 01:14:44 +0000

The challenge

Given an array of n integers nums, a 132 pattern is a subsequence of three integers nums[i], nums[j] and nums[k] such that i < j < k and nums[i] < nums[k] < nums[j].

Return true if there is a 132 pattern in nums, otherwise, return false.

**Follow up: **The O(n^2) is trivial, could you come up with the O(n logn) or the O(n) solution?

Example 1:

Example 2:

How to Replace all Vowels in a String in Java

Sun, 25 Oct 2020 00:23:30 +0000

The challenge

Replace all vowel to exclamation mark in the sentence. aeiouAEIOU is vowel.

Examples

replace("Hi!") === "H!!"
replace("!Hi! Hi!") === "!H!! H!!"
replace("aeiou") === "!!!!!"
replace("ABCDE") === "!BCD!"

The solution in Java code

We could use a StringBuilder and a switch case as a first attempt:

public class Solution {
    public static String replace(final String s) {
      StringBuilder sb = new StringBuilder();
      for (int i=0; i<s.length(); i++) {
        switch(Character.toLowerCase(s.charAt(i))) {
            case 'a':
            case 'e':
            case 'i':
            case 'o':
            case 'u':
              sb.append("!");
              break;
            default:
              sb.append(s.charAt(i));
              break;
        }
      }
      return sb.toString();
    }
}

A more efficient method using replaceAll:

How to Get the N-th Power in Java

Sat, 24 Oct 2020 03:40:09 +0000

The challenge

You are given an array with positive numbers and a number N. You should find the N-th power of the element in the array with the index N. If N is outside of the array, then return -1. Don’t forget that the first element has the index 0.

Let’s look at a few examples:

array = [1, 2, 3, 4] and N = 2, then the result is 3^2 == 9;
array = [1, 2, 3] and N = 3, but N is outside of the array, so the result is -1.

The solution in Java code

public class Solution {
  public static int nthPower(int[] array, int n) {
    return n >= array.length ? -1 : (int) Math.pow(array[n], n);
  }
}

An alternative mapping:

How to Count the Minimum Depth of a Binary Tree in Java

Fri, 23 Oct 2020 01:51:39 +0000

The challenge

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Note: A leaf is a node with no children.

Example 1:

Example 2:

Constraints:

The number of nodes in the tree is in the range [0, 105].
-1000 <= Node.val <= 1000

The definition for a binary tree node

 public class TreeNode {
     int val;
     TreeNode left;
     TreeNode right;
     TreeNode() {}
     TreeNode(int val) { this.val = val; }
     TreeNode(int val, TreeNode left, TreeNode right) {
         this.val = val;
         this.left = left;
         this.right = right;
     }
 }

The solution in Java code

First we need to make sure that we catch our 2 edge cases:

How to Solve the House Robber II Challenge in Java

Thu, 22 Oct 2020 01:35:42 +0000

The challenge

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, adjacent houses have a security system connected, and it will automatically contact the police if two adjacent houses were broken into on the same night.

How to Clone a Graph in Java

Wed, 21 Oct 2020 00:01:25 +0000

The challenge

Given a reference of a node in a connected undirected graph.

Return a deep copy (clone) of the graph. Effectively a graph copy.

Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.

class Node {
    public int val;
    public List<Node> neighbors;
}

Test case format:

How to Return Random Values in Java

Tue, 20 Oct 2020 00:54:36 +0000

The challenge

Ghost objects are instantiated without any arguments.

Ghost objects are given a random color attribute of white" or “yellow” or “purple” or “red” when instantiated

Ghost ghost = new Ghost();
ghost.getColor(); //=> "white" or "yellow" or "purple" or "red"

All this challenge is really asking us to do is to create a class method that can return random colour strings when called.

The solution in Java

We make use of the java.util.Random class to generate a couple of random values for us to use within a switch statement.

How to Compare Version Numbers in Java

Mon, 19 Oct 2020 00:50:39 +0000

The challenge

Compare two version numbers version1 and version2.
If version1 > version2 return 1; if version1 < version2 return -1;otherwise return ``.

You may assume that the version strings are non-empty and contain only digits and the . character.

The . character does not represent a decimal point and is used to separate number sequences.

For instance, 2.5 is not “two and a half” or “half way to version three”, it is the fifth second-level revision of the second first-level revision.

How to Return the First N Elements in Java

Sun, 18 Oct 2020 02:54:22 +0000

The challenge

Create a method take that accepts a list/array and a number n, and returns a list/array array of the first n elements from the list/array.

If you need help, here’s a reference:

https://docs.oracle.com/javase/6/docs/api/java/util/Arrays.html#copyOfRange(int[],%20int,%20int)

Test cases

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;
import java.util.*;

public class SolutionTest {
    @Test
    public void basicTests() {
        assertArrayEquals("should return the first 3 items", new int[]{0, 1, 2}, ZywOo.take(new int[]{0, 1, 2, 3, 5, 8, 13}, 3));
        assertArrayEquals("should return 0 items", new int[0], ZywOo.take(new int[]{0, 1, 2, 3, 5, 8, 13}, 0));
        assertArrayEquals("empty array should return empty array", new int[0], ZywOo.take(new int[0], 3));
    }
    
    @Test
    public void randomTests() {
      for (int i = 0; i < 100; i++) {
        int n = (int)Math.floor(100 * Math.random());
        int[] randomArray = generateRandomArray();
        
        assertArrayEquals("Testing with array " + Arrays.toString(randomArray) + " and n = " + n, solution(randomArray, n), ZywOo.take(randomArray, n));
      }
     
    }
    
    private int[] solution(int[] arr, int n) {
      return arr.length > 0 && arr.length > n ? Arrays.copyOfRange(arr, 0, n) : arr;
    }
    
    private int[] generateRandomArray() {
      int length = (int)Math.floor(100 * Math.random());
      int min = (int)Math.floor(-100 * Math.random());
      int max = (int)Math.floor( 100 * Math.random());
      return new Random().ints(length, min, max).toArray();
    }
}

The solution in Java

Option 1:

How to Search a 2d Matrix/Array in Java

Sat, 17 Oct 2020 00:47:45 +0000

The challenge

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

Integers in each row are sorted from left to right.
The first integer of each row is greater than the last integer of the previous row.

Example 1:

Example 2:

Example 3:

Calculate the Surface Area and Volume of a Box with Java

Fri, 16 Oct 2020 01:51:29 +0000

The challenge

Write a function that returns the total surface area and volume of a box as an array: [area, volume]

The solution in Java

We know that the formula to calculate the area of a box is as follows:

2(h × W) + 2(h × L) + 2(W × L)

We also know that the formula to calculate the volume of a box is as follows:

W x h x H

Find Numbers which are Divisible by given Number in Java

Thu, 15 Oct 2020 09:11:58 +0000

The challenge

Complete the function which takes two arguments and returns all numbers which are divisible by the given divisor. First argument is an array of numbers and the second is the divisor.

Example

divisibleBy([1, 2, 3, 4, 5, 6], 2) == [2, 4, 6]

The solution in Java

Option 1 (using streams):

import java.util.stream.*;
import java.util.Arrays;

public class EvenNumbers {
  public static int[] divisibleBy(int[] numbers, int divider) {
  
    return Arrays.stream(numbers)
                 .filter(i -> (i % divider) == 0)
                 .toArray();
  }
}

Option 2 (writing the code ourselves):

How to Split a Subdirectory to a New Git Repository and Keep the History

Wed, 14 Oct 2020 09:34:46 +0000

There comes a time when you need to split out a subdirectory into it’s own git repo.

This is a very simple task if you don’t care about persisting the git history for any changes that were made in that subdirectory.

However, if you would like to keep all the history of the subdirectory only, and not of the overall entire repository itself, then you can perform the following bunch of steps:

Get the Maximum XOR of Two Numbers in an Array in Java

Tue, 13 Oct 2020 02:12:48 +0000

The challenge

Given a non-empty array of numbers, a, a1, a2, … , an-1, where 0 ≤ ai < 231.

Find the maximum result of ai XOR aj, where 0 ≤ i, j < n.

How to Get the Opposite of a Number in Java

Mon, 12 Oct 2020 09:28:09 +0000

The challenge

Given a number, find its opposite.

Examples:

1: -1
14: -14
-34: 34

The solution in Java

We return the number itself multiplied by a negative 1.

public class Solution {
    public static int opposite(int number) {
        return number *= -1;
    }
}

This can be simplified further as:

public class Solution {
    public static int opposite(int number) {
        return -number;
    }
}

There is also a built in method to help with this if you prefer, called Math.negateExact():

How to Find the Area or Perimeter of a 4-sided Polygon using Java

Sun, 11 Oct 2020 11:12:02 +0000

The challenge

You are given the length and width of a 4-sided polygon. The polygon can either be a rectangle or a square.
If it is a square, return its area. If it is a rectangle, return its perimeter.

area_or_perimeter(6, 10) --> 32
area_or_perimeter(4, 4) --> 16

The solution in Java

Given that we know that:

The area of a square is: l x h and the area of a rectangle is 2(l+h), we can create the following code, differentiating on the if conditional statement that l==w, or, length is equal to width, which would mean a square, otherwise a rectangle:

How to Parse Int from Char in Java

Sat, 10 Oct 2020 00:31:04 +0000

The challenge

We take in a String where the first place contains a number, write a function that takes in this String and returns an int containing it.

For correct answer program should return int from 0 to 9.

Assume test input string always valid and may look like “1 year old” or “5 years old”, etc.. The first char is number only.

The solution in Java

We take in a String, and get the first character, which is done by using charAt(0). As this is a char type, we can append a -'0' to it and cast it back to an int using (ing):

How to Search a Binary Tree in Java

Fri, 09 Oct 2020 10:06:07 +0000

The challenge

Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1.

Example 1:

Example 2:

Note:

You may assume that all elements in nums are unique.
n will be in the range [1, 10000].
The value of each element in nums will be in the range [-9999, 9999].

The solution in Java code

We call the search() method which recursively calls the binarySearch() method for each level.

How to Rotate a Singly Linked List in Java

Thu, 08 Oct 2020 00:47:45 +0000

The challenge

Given a linked list, rotate the list to the right by k places, where k is non-negative.

Example 1:

Example 2:

How to Insert into a Binary Search Tree using Java

Wed, 07 Oct 2020 00:57:16 +0000

The challenge

You are given the root node of a binary search tree (BST) and a value to insert into the tree. Return the root node of the BST after the insertion. It is guaranteed that the new value does not exist in the original BST.

Notice that there may exist multiple valid ways for the insertion, as long as the tree remains a BST after insertion. You can return any of them.

Find the Complement of Base 10 Integer in Java

Tue, 06 Oct 2020 08:44:41 +0000

The challenge

Every non-negative integer N has a binary representation. For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on. Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a  and  to a 1. For example, the complement of "101" in binary is "010" in binary.

Solve the Number of Recent Calls Challenge in Java

Mon, 05 Oct 2020 01:05:12 +0000

The challenge

You have a RecentCounter class which counts the number of recent requests within a certain time frame.

Implement the RecentCounter class:

RecentCounter() Initializes the counter with zero recent requests.
int ping(int t) Adds a new request at time t, where t represents some time in milliseconds, and returns the number of requests that has happened in the past 3000 milliseconds (including the new request). Specifically, return the number of requests that have happened in the inclusive range [t - 3000, t].

It is guaranteed that every call to ping uses a strictly larger value of t than the previous call.

How to Calculate the Summation of a Number in Java

Sun, 04 Oct 2020 02:53:02 +0000

The challenge

Write a program that finds the summation of every number from 1 to num. The number will always be a positive integer greater than 0.

For example:

summation(2) -> 3
1 + 2

summation(8) -> 36
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8

The solution in Java

public class Solution {

    public static int summation(int n) {
        int runningTotal = 0;
      
        for (int i=1; i<=n; i++) runningTotal += i;
      
        return runningTotal;
    }
}

A simpler alternative is to do the following:

How to Calculate all Unique Combinations of a Target using Backtracking in Java

Sat, 03 Oct 2020 02:39:08 +0000

The challenge

Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.

The same number may be chosen from candidates an unlimited number of times. Two combinations are unique if the frequency of at least one of the chosen numbers is different.

Example 1:

Who is going to pay for the wall? in Python

Fri, 02 Oct 2020 01:54:33 +0000

The challenge

Don Drumphet lives in a nice neighborhood, but one of his neighbors has started to let his house go. Don Drumphet wants to build a wall between his house and his neighbor’s, and is trying to get the neighborhood association to pay for it. He begins to solicit his neighbors to petition to get the association to build the wall. Unfortunately for Don Drumphet, he cannot read very well, has a very limited attention span, and can only remember two letters from each of his neighbors’ names. As he collects signatures, he insists that his neighbors keep truncating their names until two letters remain, and he can finally read them.

Calculate the Total Amount of Points using Java

Thu, 01 Oct 2020 00:47:40 +0000

The challenge

Our football team finished the championship. The result of each match look like “x:y”. Results of all matches are recorded in the collection.

For example: ["3:1", "2:2", "0:1", ...]

Write a function that takes such collection and counts the points of our team in the championship. Rules for counting points for each match:

if x>y – 3 points
if x<y – 0 point
if x=y – 1 point

Notes:

Calculate the biggest of 3 numbers using Java

Wed, 30 Sep 2020 02:00:38 +0000

The challenge

Task

Given three integers a ,b ,c, return the largest number obtained after inserting the following operators and brackets: +, *, ()
In other words , try every combination of a,b,c with [*+()] , and return the Maximum Obtained

Consider an Example :

With the numbers are 1, 2 and 3 , here are some ways of placing signs and brackets:

1 * (2 + 3) = 5
1 * 2 * 3 = 6
1 + 2 * 3 = 7
(1 + 2) * 3 = 9

So the maximum value that you can obtain is 9.

Find the missing element between two arrays in Python

Tue, 29 Sep 2020 08:52:39 +0000

The challenge

Given two integer arrays where the second array is a shuffled duplicate of the first array with one element missing, find the missing element.

Please note, there may be duplicates in the arrays, so checking if a numerical value exists in one and not the other is not a valid solution.

find_missing([1, 2, 2, 3], [1, 2, 3]) => 2

find_missing([6, 1, 3, 6, 8, 2], [3, 6, 6, 1, 2]) => 8

The first array will always have at least one element.

How to Count an Array of Boolean Values in Java

Mon, 28 Sep 2020 01:04:49 +0000

The challenge

Consider an array/list of sheep where some sheep may be missing from their place. We need a function that counts the number of sheep present in the array (true means present).

For example,

[true,  true,  true,  false,
  true,  true,  true,  true ,
  true,  false, true,  false,
  true,  false, false, true ,
  true,  true,  true,  true ,
  false, false, true,  true]

The correct answer would be 17.

Hint: Don’t forget to check for bad values like null/undefined

How to Solve the Car Pooling Challenge in Java

Sun, 27 Sep 2020 01:18:07 +0000

The challenge

You are driving a vehicle that has capacity empty seats initially available for passengers. The vehicle only drives east (ie. it cannot turn around and drive west.)

Given a list of trips, trip[i] = [num_passengers, start_location, end_location] contains information about the i-th trip: the number of passengers that must be picked up, and the locations to pick them up and drop them off. The locations are given as the number of kilometers due east from your vehicle’s initial location.

How to Repeat a String in Java

Sat, 26 Sep 2020 03:03:07 +0000

The challenge

Write a function called repeat_str which repeats the given string src exactly count times.

repeatStr(6, "I") // "IIIIII"
repeatStr(5, "Hello") // "HelloHelloHelloHelloHello"

The solution in Java

Java comes with a built-in on the String class. Called repeat, which allows you to very easily repeat that string n number of times.

"Hello".repeat(2); // "HelloHello"

Using String::repeat()

Therefore, we could solve our above problem as follows:

class Solution {
  static String repeatStr(int repeat, String string) {
    return string.repeat(repeat);
  }
}

Obviously, we probably want to validate our input before we just do it, so maybe wrap it in a ternary:

How to Find the Smallest Integer in the Array in Java

Fri, 25 Sep 2020 01:58:50 +0000

The challenge

Given an array of integers your solution should find the smallest integer.

For example:

Given [34, 15, 88, 2] your solution will return 2
Given [34, -345, -1, 100] your solution will return -345

You can assume, for the purpose of this challenge, that the supplied array will not be empty.

The solution in Java

Option 1 (using Arrays.sort):

import java.util.Arrays;

public class SmallestIntegerFinder {
    public static int findSmallestInt(int[] args) {

        Arrays.sort(args);
      
        return args[0];
    }
}

Option 2 (using streams):

How to Count Odd Numbers Below N using Java

Thu, 24 Sep 2020 08:51:02 +0000

The challenge

Given a number n, return the number of positive odd numbers below n, EASY!

oddCount(7) //=> 3, i.e [1, 3, 5]
oddCount(15) //=> 7, i.e [1, 3, 5, 7, 9, 11, 13]

Expect large Inputs!

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void fixedTests() {
        assertEquals(7, OddNumbers.oddCount(15));
        assertEquals(7511, OddNumbers.oddCount(15023));
    }
}

The solution in Java

At first we would approach this in a programming type of way:

How to get the Length of the Last Word in a String using Java

Wed, 23 Sep 2020 02:34:43 +0000

The challenge

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word (last word means the last appearing word if we loop from left to right) in the string.

If the last word does not exist, return 0.

Note: A word is defined as a maximal substring consisting of non-space characters only.

Example:

The solution in Java

class Solution {
    public int lengthOfLastWord(String s) {
        // catch edge case of blank input
        if (s.length()<=0) return 0;
        
        // split into words
        String[] words = s.split("\\s+");
        
        // if one or less words, then return the length of the trimmed string
        if (words.length<=1) return s.trim().length();
        
        // get the alst word
        String lastWord = words[words.length-1];
        
        // return the last word's length
        return lastWord.length();
        
    }
}

How to Convert a Number to Reversed Array of Digits in Java

Tue, 22 Sep 2020 02:16:11 +0000

The challenge

Given a random non-negative number, you have to return the digits of this number within an array in reverse order.

Test cases

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;

public class DigitizeExampleTests {
  @Test
  public void tests() {
    assertArrayEquals(new int[] {1, 3, 2, 5, 3}, ConvertAndReverse.digitize(35231));
  }
}

Solution in Java

Option 1 (using Streams and StringBuilder):

import java.util.*;

public class ConvertAndReverse {
  public static int[] digitize(long n) {
    StringBuilder sb = new StringBuilder(Long.toString(n)).reverse();
    
    return Arrays.stream(sb.toString().split(""))
                  .mapToInt(Integer::parseInt)
                  .toArray();
  }
}

Option 2 (using StringBuilder and Streams):

How to Solve Unique Paths III in Java

Mon, 21 Sep 2020 08:08:15 +0000

The challenge

On a 2-dimensional grid, there are 4 types of squares:

1 represents the starting square. There is exactly one starting square.
2 represents the ending square. There is exactly one ending square.
`` represents empty squares we can walk over.
-1 represents obstacles that we cannot walk over.

Return the number of 4-directional walks from the starting square to the ending square, that walk over every non-obstacle square exactly once.

How to Find the Mean/Average of a List of Numbers in Java

Sun, 20 Sep 2020 02:00:23 +0000

The challenge

Find the mean (average) of a list of numbers in an array.

To find the mean (average) of a set of numbers add all of the numbers together and divide by the number of values in the list.

For an example list of 1, 3, 5, 7

1. Add all of the numbers

1+3+5+7 = 16

2. Divide by the number of values in the list. In this example there are 4 numbers in the list.

How to Calculate BMI in Java

Sat, 19 Sep 2020 02:00:26 +0000

The challenge

BMI stands for Body Mass Index and is a value derived from the mass and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m², resulting from mass in kilograms and height in metres. Wikipedia

Write function BMI that calculates body mass index (bmi = weight / height ^ 2).

How to Solve the Robot Bounded In Circle Challenge in Java

Fri, 18 Sep 2020 01:14:11 +0000

The challenge

On an infinite plane, a robot initially stands at (0, 0) and faces north. The robot can receive one of three instructions:

"G": go straight 1 unit;
"L": turn 90 degrees to the left;
"R": turn 90 degress to the right.

The robot performs the instructions given in order, and repeats them forever.

Return true if and only if there exists a circle in the plane such that the robot never leaves the circle.

How to Convert a String to a Number in Java

Thu, 17 Sep 2020 01:56:05 +0000

The challenge

We need a function that can transform a string into a number. What ways of achieving this do you know?

Note: Don’t worry, all inputs will be strings, and every string is a perfectly valid representation of an integral number.

Examples

stringToNumber("1234") == 1234
stringToNumber("605" ) == 605
stringToNumber("1405") == 1405
stringToNumber("-7"  ) == -7

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class StringToNumberTest {   
    @Test
    public void test1(){
      assertEquals("stringToNumber(1234)", 1234 , StringToNumber.stringToNumber("1234"));
    }
    @Test
    public void test2(){
      assertEquals("stringToNumber(605)", 605 , StringToNumber.stringToNumber("605"));
    }
    @Test
    public void test3(){
      assertEquals("stringToNumber(1405)", 1405 , StringToNumber.stringToNumber("1405"));
    }
    @Test
    public void test4(){
      assertEquals("stringToNumber(-7)", -7 , StringToNumber.stringToNumber("-7"));
    }
    @Test
    public void test5(){
      for(int i = 0; i < 100; ++i) {
        int t = (int)Math.round(Math.random() * 500000);
        assertEquals("stringToNumber(" + t + ")", t , StringToNumber.stringToNumber(Integer.toString(t)));
      }
    }
}

The solution in Java

Option 1 (using parseInt):

How to Convert an Integer to Binary using Java

Wed, 16 Sep 2020 00:58:09 +0000

The challenge

Given a non-negative integer n, write a function toBinary/ToBinary which returns that number in a binary format.

to_binary(1)  /* should return 1 */
to_binary(5)  /* should return 101 */
to_binary(11) /* should return 1011 */

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;


public class ConvertTest {
    @Test
    public void testToBinary() {
  		assertEquals(1, BinaryConvert.toBinary(1));
  		assertEquals(10, BinaryConvert.toBinary(2));
  		assertEquals(11, BinaryConvert.toBinary(3));
  		assertEquals(101, BinaryConvert.toBinary(5));
    }
}

The solution in Java

public class BinaryConvert {

  public static int toBinary(int n) {
    // Use the `toBinaryString` method of the Integer class
    // convert it back to an `int` using the `parseInt` method of the Integer class
    // return the result
    return Integer.parseInt(Integer.toBinaryString(n));
  }

}

Alternative 1:

How to create a Logical Operator in Java

Tue, 15 Sep 2020 01:43:17 +0000

Exclusive “or” (xor) Logical Operator

In some scripting languages like PHP, there exists a logical operator (e.g. &&, ||, and, or, etc.) called the “Exclusive Or”. The exclusive or evaluates two booleans. It then returns true if exactly one of the two expressions are true, false otherwise. For example:

// since both are false
false xor false == false

// exactly one of the two expressions are true
true xor false == true

// exactly one of the two expressions are true
false xor true == true

// Both are true.  "xor" only returns true if EXACTLY one of the two expressions evaluate to true.
true xor true == false

How to create a Logical Operator in Java

As Java does not ship out the box with this functionality, we can easily create it ourselves.

How to merge sorted integer arrays (without duplicates) in Java

Mon, 14 Sep 2020 01:08:12 +0000

The challenge

Write a function that merges two sorted arrays into a single one. The arrays only contain integers. Also, the final outcome must be sorted and not have any duplicate.

Test cases

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.function.Function;
import java.util.stream.IntStream;

public class SolutionTest {

  @Test
  public void fixedTest() {

    assertArrayEquals(new int[] { 1, 2, 3, 4, 5, 6 }, Merger.mergeArrays(new int[] { 1, 3, 5 }, new int[] { 2, 4, 6 }));
    assertArrayEquals(new int[] { 2, 4, 6, 8 }, Merger.mergeArrays(new int[] { 2, 4, 8 }, new int[] { 2, 4, 6 }));
    assertArrayEquals(new int[] { 1, 2, 3 }, Merger.mergeArrays(new int[] { 1, 2, 3 }, new int[] {}));
    assertArrayEquals(new int[0], Merger.mergeArrays(new int[0], new int[0]));

    assertArrayEquals(IntStream.rangeClosed(1, 15).toArray(), Merger.mergeArrays(IntStream.rangeClosed(1, 10).toArray(), IntStream.rangeClosed(5, 15).toArray()));
    assertArrayEquals(new int[] { 1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15 }, Merger.mergeArrays(IntStream.rangeClosed(1, 5).toArray(), IntStream.rangeClosed(10, 15).toArray()));
    assertArrayEquals(IntStream.rangeClosed(-5, 20).toArray(), Merger.mergeArrays(IntStream.rangeClosed(-5, 10).toArray(), IntStream.rangeClosed(-2, 20).toArray()));
  }

  private static final Random rnd = new Random();

  @Test
  public void randomTest() {

    for (int i = 0; i < 100; ++i) {

      int[] source = IntStream.generate(() -> { return rnd.nextInt(200) - 100; }).limit(200).distinct().sorted().toArray();
      List<Integer> one = new ArrayList<>();
      List<Integer> two = new ArrayList<>();

      for (int num : source) {

        (rnd.nextBoolean() ? one : two).add(num);

        if (rnd.nextInt(10) < 2)
          (rnd.nextBoolean() ? one : two).add(num);

      }

      Function<List<Integer>, int[]> asPrimitive = array -> array.stream().mapToInt(n -> n.intValue()).toArray();
      assertArrayEquals(source, Merger.mergeArrays(asPrimitive.apply(one), asPrimitive.apply(two)));
    }
  }
}

The solution in Java

Option 1 (using streams):

Find the Force of Gravity Between Two Objects with Java

Sun, 13 Sep 2020 01:23:27 +0000

The challenge

Your job is to find the gravitational force between two spherical objects (obj1 , obj2).

Two arrays are give :

arr_val (value array), consists of 3 elements
- 1st element : mass of obj 1
- 2nd element : mass of obj 2
- 3rd element : distance between their centers
arr_unit (unit array), consists of 3 elements
- 1st element : unit for mass of obj 1
- 2nd element : unit for mass of obj 2
- 3rd element : unit for distance between their centers

Mass units are :

kilogram (kg)
gram (g)
milligram (mg)
microgram (μg)
pound (lb)

Distance units are :

meter (m)
centimeter (cm)
millimeter (mm)
micrometer (μm)
feet (ft)

Additional notes

value of G = 6.67 x 10-11N.kg–2.m2

How to zoom text by mouse wheel in IntelliJ Idea

Sat, 12 Sep 2020 02:35:35 +0000

It’s a common requirement to be able to zoom in or out while working in the code editor in IntelliJ Idea.

This is achieved on Windows with CTRL+Mouse Wheel, or on Mac with CMD+Mouse Wheel.

This feature is not enabled by default, but luckily it’s very simple to enable this.

How to enable mouse wheel zoom in IntelliJ

Open the Settings, or Preferences window.

On Windows you can press CTRL+ALT+S, and on Mac you can press CMD+,

Playing the Bulls and Cows Game in Java

Fri, 11 Sep 2020 02:36:10 +0000

The challenge

You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called “bulls”) and how many digits match the secret number but locate in the wrong position (called “cows”). Your friend will use successive guesses and hints to eventually derive the secret number.

Calculate the Sum of Root To Leaf Binary Numbers in Java

Thu, 10 Sep 2020 01:36:58 +0000

The challenge

Given a binary tree, each node has value `` or 1. Each root-to-leaf path represents a binary number starting with the most significant bit. For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.

For all leaves in the tree, consider the numbers represented by the path from the root to that leaf.

Remove an Exclamation Mark from the End of String using Python

Wed, 09 Sep 2020 01:39:39 +0000

The challenge

Remove a exclamation mark from the end of string. You can assume that the input data is always a string, no need to verify it.

Examples

remove("Hi!") === "Hi"
remove("Hi!!!") === "Hi!!"
remove("!Hi") === "!Hi"
remove("!Hi!") === "!Hi"
remove("Hi! Hi!") === "Hi! Hi"
remove("Hi") === "Hi"

Test cases

test.describe("Basic Tests")

tests = [
    #[input, [expected]],
    ["Hi!", "Hi"],
    ["Hi!!!","Hi!!"],
    ["!Hi", "!Hi"],
    ["!Hi!", "!Hi"],
    ["Hi! Hi!", "Hi! Hi"],
    ["Hi", "Hi"],
]

for inp, exp in tests:
    test.assert_equals(remove(inp), exp)

The solution in Python

Option 1:

How to “Rock Paper Scissors” in Java

Tue, 08 Sep 2020 01:35:04 +0000

The challenge

Let’s play Rock Paper Scissors! You have to return which player won! In case of a draw return Draw!.

Examples:

rps('scissors','paper') // Player 1 won!
rps('scissors','rock') // Player 2 won!
rps('paper','paper') // Draw!

The rules of the game Rock Paper Scissors

The rules of the game Rock Paper Scissors is quite simple.

Rock beats scissors, scissors beats paper, and paper beats rock.

Below is an illustration showing the cyclical routes.

Compare within Margin using Python

Mon, 07 Sep 2020 08:15:35 +0000

The challenge

Create a function close_compare that accepts 3 parameters: a, b, and an optional margin. The function should return whether a is lower than, close to, or higher than b. a is “close to” b if margin is higher than or equal to the difference between a and b.

When a is lower than b, return -1.

When a is higher than b, return 1.

When a is close to b, return ``.

Get the mean of an array in Java

Sun, 06 Sep 2020 10:40:05 +0000

The challenge

It’s the academic year’s end, fateful moment of your school report. The averages must be calculated. All the students come to you and entreat you to calculate their average for them. Easy ! You just need to write a script.

Return the average of the given array rounded down to its nearest integer.

The array will never be empty.

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;


public class SolutionTest {
  	@Test
	public void simpleTest() {
		assertEquals(2,School.getAverage(new int[] {2,2,2,2}));
		assertEquals(3,School.getAverage(new int[] {1,2,3,4,5}));
		assertEquals(1,School.getAverage(new int[] {1,1,1,1,1,1,1,2}));
	}
  

  
}

The solution in Java

Option 1:

Remove the time challenge in Python

Sat, 05 Sep 2020 10:51:04 +0000

The challenge

You’re re-designing a blog and the blog’s posts have the following format for showing the date and time a post was made:

Weekday Month Day, time e.g., Friday May 2, 7pm

You’re running out of screen real estate, and on some pages you want to display a shorter format, Weekday Month Day that omits the time.

Write a function, shortenToDate, that takes the Website date/time in its original string format, and returns the shortened format.

How to Convert Hex to Decimal in Java

Fri, 04 Sep 2020 08:42:52 +0000

The challenge

Write a function that converts an input string contains a hex value, and return a decimal.

Test cases

import org.junit.Test;
import static org.junit.Assert.*;

public class ExampleTests {

  @Test
  public void examples() {
      // assertEquals("expected", "actual");
      assertEquals(1, ConvertHexToDec.hexToDec("1"));
      assertEquals(10, ConvertHexToDec.hexToDec("a"));
      assertEquals(16, ConvertHexToDec.hexToDec("10"));
      assertEquals(255, ConvertHexToDec.hexToDec("FF"));
      assertEquals(-12, ConvertHexToDec.hexToDec("-C"));
  }
  
}

The solution in Java

In Java, it is really easy to convert Hex to Decimal.

You simply use the Integer class and call the parseInt method, making sure to also provide the base that you want to convert from.

Character with Longest Consecutive Repetition in Java

Thu, 03 Sep 2020 01:21:09 +0000

The challenge

For a given string s find the character c (or C) with longest consecutive repetition and return:

Object[]{c, l};

where l (or L) is the length of the repetition. If there are two or more characters with the same l return the first in order of appearance.

For empty string return:

Object[]{"", 0}

Test cases

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void exampleTests() {
        assertArrayEquals(new Object[]{"a", 4}, Solution.longestRepetition("aaaabb"));
        assertArrayEquals(new Object[]{"a", 4}, Solution.longestRepetition("bbbaaabaaaa"));
        assertArrayEquals(new Object[]{"u", 3}, Solution.longestRepetition("cbdeuuu900"));
        assertArrayEquals(new Object[]{"b", 5}, Solution.longestRepetition("abbbbb"));
        assertArrayEquals(new Object[]{"a", 2}, Solution.longestRepetition("aabb"));
        assertArrayEquals(new Object[]{"", 0}, Solution.longestRepetition(""));
    }
}

The solution in java

Option 1:

Check if List contains Item in Python

Wed, 02 Sep 2020 01:19:41 +0000

The challenge

Create a method that accepts a list and an item, and returns true if the item belongs to the list, otherwise false.

Test cases

list = [0,1,2,3,5,8,13,2,2,2,11];
Test.assert_equals(include(list, 100), False, "list does not include 100")
Test.assert_equals(include(list, 2), True, "list includes 2 multiple times")
Test.assert_equals(include(list, 11), True, "list includes 11")
Test.assert_equals(include(list, "2"), False, "list includes 2 (integer), not ''2'' (string)")
Test.assert_equals(include([], 0), False, "empty list doesn't include anything")
Test.assert_equals(include(list, 0), True, "list includes 0")

The solution in Python

def include(arr,item):
    return item in arr

How To Create a User and Grant Permissions in MySQL

Tue, 01 Sep 2020 00:32:57 +0000

How to create a user

CREATE USER 'myuser'@'localhost' IDENTIFIED BY 'mypassword';

How to delete a user

DROP USER 'myuser'@'localhost';

How to grant permissions

GRANT ALL PRIVILEGES ON * . * TO 'myuser'@'localhost';

How to apply those permissions

FLUSH PRIVILEGES;

Going a bit deeper

Different types of Grants

ALL PRIVILEGES : Full access to everything, globally unless restricted to a database

CREATE : Create databases and tables

DROP : Delete databases and tables

DELETE : Delete rows from tables

How to Remove Vowels with Python

Mon, 31 Aug 2020 00:37:31 +0000

The challenge

Create a function called shortcut to remove all the lowercase vowels in a given string.

Examples

shortcut("codewars") # --> cdwrs
shortcut("goodbye")  # --> gdby

Don’t worry about uppercase vowels.

Test cases

import random

Test.describe("Easy")
for t in [
  ["hello","hll"],
  ["hellooooo","hll"],
  ["how are you today?","hw r y tdy?"],
  ["complain","cmpln"],
  ["never","nvr"]
]:
    ans,exp = shortcut(t[0]), t[1]
    Test.assert_equals(ans,exp)

Test.describe("Not so easy")
for t in [
  ["a e i o u, borriquito como tu","    , brrqt cm t","Isolated vowels let spaces between them"],
  ["Explicit is better than implicit", "Explct s bttr thn mplct","Should remove only lowercase vowel"],
  ["Beautiful is better than Ugly", "Btfl s bttr thn Ugly","Should remove only lowercase vowel"]
]:
    ans,exp = shortcut(t[0]), t[1]
    Test.assert_equals(ans,exp)

#  
for t in random.sample([
  ["We are the Knights who say ni!","W r th Knghts wh sy n!"],
  ["Nobody expects the Spanish Inquisition!","Nbdy xpcts th Spnsh Inqstn!"],
  ["He's not the messiah. He's a very naughty boy!","H's nt th mssh. H's  vry nghty by!"],
  ["It's just a flesh wound.","It's jst  flsh wnd."],
  ["You don't frighten us, English pig dogs.","Y dn't frghtn s, Englsh pg dgs."],
  ["Mate, this parrot wouldn't VOOM if you put four million volts through it!","Mt, ths prrt wldn't VOOM f y pt fr mlln vlts thrgh t!"],
  ["Five is a sufficiently close approximation to infinity.","Fv s  sffcntly cls pprxmtn t nfnty."]
],7):
    ans,exp = shortcut(t[0]), t[1]
    Test.assert_equals(ans,exp)

The solution in Python

Option 1 (long way):

How to find all files in a directory with extension

Sun, 30 Aug 2020 01:05:29 +0000

I needed to find all files in a directory on Linux that ended with the file extension .php.

How to find all files in a directory with extension

You can do this as follows:

cd <your directory path>

find . -type f -name "*.php"

How to find other file extensions in a directory

Just swap out the .php value for another file extension that you would like to search for instead.

How to Sort a List in Python

Sat, 29 Aug 2020 01:30:04 +0000

In this tutorial, you will learn how to sort a list in Python, by following the below three steps:

Options to sort a list in Python
- What is the difference between “sort” and “sorted”
- An example of using “sort”
- An example of using “sorted”
How to Sort a List in Reverse
- Sort a list in Reverse using “sort”
- Sort a list in Reverse using “sorted”
Sort with a Custom Function using Key

1. Options to sort a list in Python

There exist two main options, those are sort() and sorted(), let’s explore them below.

Cryptanalysis Word Patterns in Java

Fri, 28 Aug 2020 00:58:47 +0000

The challenge

In cryptanalysis, words patterns can be a useful tool in cracking simple ciphers.

A word pattern is a description of the patterns of letters occurring in a word, where each letter is given an integer code in order of appearance. So the first letter is given the code 0, and second is then assigned 1 if it is different to the first letter or 0 otherwise, and so on.

How to divide a number in Python

Thu, 27 Aug 2020 09:10:44 +0000

The challenge

Your task is to create functionisDivideBy (or is_divide_by) to check if an integer number is divisible by each out of two arguments.

A few cases:

(-12, 2, -6)  ->  true
(-12, 2, -5)  ->  false

(45, 1, 6)    ->  false
(45, 5, 15)   ->  true

(4, 1, 4)     ->  true
(15, -5, 3)   ->  true

Test cases

Test.describe("Basic Tests")
Test.it("should pass basic tests")
Test.assert_equals(is_divide_by(-12, 2, -6), True)
Test.assert_equals(is_divide_by(-12, 2, -5), False)
Test.assert_equals(is_divide_by(45, 1, 6), False)
Test.assert_equals(is_divide_by(45, 5, 15), True)
Test.assert_equals(is_divide_by(4, 1, 4), True)
Test.assert_equals(is_divide_by(15, -5, 3), True)

Understanding how to solve this

To resolve this problem, we need to understand how to find if a number can be divided without a remainder in Python. This is similar to other mathematical operations you might perform in Python, like finding the intersection of two arrays or converting RGB to Hex.

How to Read Kubernetes Secrets

Wed, 26 Aug 2020 03:10:34 +0000

Kubernetes secrets is a great way to store secret values that only Kubernetes can access in your hosted applications.

There are times when you might need to view these secrets in plain-text. This is probably because you want to validate the value or use it manually elsewhere.

In this tutorial we will go through how to achieve this and read Kubernetes secrets using kubectl for the command-line.

tl;dr

kubectl get secret <SECRET_NAME> -o jsonpath="{.data.<DATA>}" | base64 --decode

In the above sample code, simply replace <SECRET_NAME> and <DATA> with your own values.

Backspaces in String Challenge using Java

Tue, 25 Aug 2020 09:57:27 +0000

The challenge

Assume "#" is like a backspace in string. This means that string "a#bc#d" actually is "bd"

Your task is to process a string with "#" symbols.

Examples

"abc#d##c"      ==>  "ac"
"abc##d######"  ==>  ""
"#######"       ==>  ""
""              ==>  ""

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void testCleanString() {
        final BackspacesInString bis = new BackspacesInString();
        assertEquals("ac", bis.cleanString("abc#d##c"));
        assertEquals("", bis.cleanString("abc####d##c#"));
    }
}

The solution in Java

Option 1:

How many times to Kaprekar’s constant using Python

Mon, 24 Aug 2020 08:47:06 +0000

Introduction

6174 is known as Kaprekar’s constant after the Indian mathematician D. R. Kaprekar. This number is notable for the following rule:

Take any four-digit number, using at least two different digits (leading zeros are allowed).
Arrange the digits in descending and then in ascending order to get two four-digit numbers, adding leading zeros if necessary.
Subtract the smaller number from the bigger number.
Go back to step 2 and repeat.

The above process, known as Kaprekar’s routine, will always reach its fixed point, 6174, in at most 7 iterations. Once 6174 is reached, the process will continue yielding 7641 – 1467 = 6174. For example, choose 3524:5432 – 2345 = 30878730 – 0378 = 83528532 – 2358 = 61747641 – 1467 = 6174

How to check if a String is a Number in Python

Sun, 23 Aug 2020 03:09:28 +0000

The challenge

Given a string s, write a method (function) that will return true if its a valid single integer or floating number or false if its not.

Valid examples, should return true:

isDigit("3")
isDigit("  3  ")
isDigit("-3.23")

should return false:

isDigit("3-4")
isDigit("  3   5")
isDigit("3 5")
isDigit("zero")

Test cases

test.assert_equals(isDigit("s2324"), False)
test.assert_equals(isDigit("-234.4"), True)

The solution in Python

Option 1(with try/except):

# create a function
def isDigit(string):
    # use a `try/except` block
    try:
        # True if can convert to a float
        float(string)
        return True
    except:
        # otherwise return False
        return False

Option 2(with regex/Regular expression):

How to Write a Custom Comparator in Python

Sat, 22 Aug 2020 01:48:47 +0000

Generally, you want to use the built-in sorted() function which takes a custom comparator as its parameter. We need to pay attention to the fact that in Python 3 the parameter name and semantics have changed.

How the custom comparator works

When providing a custom comparator, it should generally return an integer/float value that follows the following pattern (as with most other programming languages and frameworks):

return a negative value (< 0) when the left item should be sorted before the right item
return a positive value (> 0) when the left item should be sorted after the right item
return `` when both the left and the right item have the same weight and should be ordered “equally” without precedence

The challenge

Write a comparator for a list of phonetic words for the letters of the greek alphabet.

How to delete an AWS WAF – Web ACL

Fri, 21 Aug 2020 01:33:00 +0000

Usually, it’s quite easy to delete an AWS WAF, or Web ACL. But sometimes you may come across the following error when attempting to delete the actual WAF:

AWS WAF couldn’t perform the operation because your resource is being used by another resource or it’s associated with another resource.

What this means

When you get this error, it means that there is something attached to the WAF that is currently using it.

How to Sort an Integer in Python

Thu, 20 Aug 2020 08:41:49 +0000

Let’s say that you have an integer with value of 9271 and you want to sort it either ascending(1279) or descending(9721).

How would you do this in Python? How would you sort an integer in either ascending or descending order?

Sorting our integer

Let’s set our integer to n:

n = 9271

Now let’s sort it:

sorted([i for i in str(n)])

# This will give us a list in ascending order
# ['1', '2', '7', '9']

We can as easily do it the other way:

How to Upgrade PIP

Wed, 19 Aug 2020 11:55:37 +0000

In this tutorial, you will learn how to upgrade PIP.

You will also learn how to check the current version of PIP, as well as downgrade to a previous version of PIP if you really need to.

TLDR; How to Upgrade PIP

The most obvious way, if python is mapped to the version you want pip to be upgraded on:

python -m pip install --upgrade pip

or if you are running python3 from the python3 command itself:

How to Copy a File in Python

Tue, 18 Aug 2020 07:46:26 +0000

In this tutorial, you will learn how to copy a file using Python from a directory to another directory, or if you’re on Windows, then from a Folder to another Folder.

shutil.copyfile is a tool that is often used to copy a file in Python, below is an example of it’s usage, you can read more about it on the Python docs:

Conway’s Game of Life – Unlimited Edition – in Python

Mon, 17 Aug 2020 07:30:17 +0000

What is this?

geeksforgeeks.org

How the game works

Because the Game of Life is built on a grid of nine squares, every cell has eight neighboring cells,as shown in the given figure. A given cell (i, j) in the simulation is accessed on a grid [i][j], where i and j are the row and column indices, respectively. The value of a given cell at a given instant of time depends on the state of its neighbors at the previous time step. Conway’s Game of Life has four rules.

Most frequently used words in a text with Python

Sun, 16 Aug 2020 02:16:11 +0000

The challenge

Write a function that, given a string of text (possibly with punctuation and line-breaks), returns an array of the top-3 most occurring words, in descending order of the number of occurrences.

Assumptions:

A word is a string of letters (A to Z) optionally containing one or more apostrophes (‘) in ASCII. (No need to handle fancy punctuation.)
Matches should be case-insensitive, and the words in the result should be lowercased.
Ties may be broken arbitrarily.
If a text contains fewer than three unique words, then either the top-2 or top-1 words should be returned, or an empty array if a text contains no words.

Examples:

top_3_words("In a village of La Mancha, the name of which I have no desire to call to
mind, there lived not long since one of those gentlemen that keep a lance
in the lance-rack, an old buckler, a lean hack, and a greyhound for
coursing. An olla of rather more beef than mutton, a salad on most
nights, scraps on Saturdays, lentils on Fridays, and a pigeon or so extra
on Sundays, made away with three-quarters of his income.")
# => ["a", "of", "on"]

top_3_words("e e e e DDD ddd DdD: ddd ddd aa aA Aa, bb cc cC e e e")
# => ["e", "ddd", "aa"]

top_3_words("  //wont won't won't")
# => ["won't", "wont"]

Bonus points:

Avoid creating an array whose memory footprint is roughly as big as the input text.
Avoid sorting the entire array of unique words.

Test cases

from random import choice, randint, sample, shuffle, choices
import re
from collections import Counter


def check(s, this=None):                                            # this: only for debugging purpose
    returned_result = top_3_words(s) if this is None else this
    fs = Counter(w for w in re.findall(r"[a-zA-Z']+", s.lower()) if w != "'" * len(w))
    exp,expected_frequencies = map(list,zip(*fs.most_common(3))) if fs else ([],[])
    
    msg = ''
    wrong_words = [w for w in returned_result if not fs[w]]
    actual_freq = [fs[w] for w in returned_result]
    
    if wrong_words:
        msg = 'Incorrect match: words not present in the string. Your output: {}. One possible valid answer: {}'.format(returned_result, exp)
    elif len(set(returned_result)) != len(returned_result):
        msg = 'The result should not contain copies of the same word. Your output: {}. One possible output: {}'.format(returned_result, exp)
    elif actual_freq!=expected_frequencies:
        msg = "Incorrect frequencies: {} should be {}. Your output: {}. One possible output: {}".format(actual_freq, expected_frequencies, returned_result, exp)
    
    Test.expect(not msg, msg)



@test.describe("Fixed tests")
def fixed_tests():

    TESTS = (
    "a a a  b  c c  d d d d  e e e e e",
    "e e e e DDD ddd DdD: ddd ddd aa aA Aa, bb cc cC e e e",
    "  //wont won't won't ",
    "  , e   .. ",
    "  ...  ",
    "  '  ",
    "  '''  ",
    """In a village of La Mancha, the name of which I have no desire to cao
    mind, there lived not long since one of those gentlemen that keep a lance
    in the lance-rack, an old buckler, a lean hack, and a greyhound for
    coursing. An olla of rather more beef than mutton, a salad on most
    nights, scraps on Saturdays, lentils on Fridays, and a pigeon or so extra
    on Sundays, made away with three-quarters of his income.""",
    "a a a  b  c c X",
    "a a c b b",
    )
    for s in TESTS: check(s)
    
@test.describe("Random tests")
def random_tests():
    
    def gen_word():
        return "".join(choice("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'") for _ in range(randint(3, 10)))
    
    def gen_string():
        words = []
        nums = choices(range(1, 31), k=20)
        for _ in range(randint(0, 20)):
            words += [gen_word()] * nums.pop()
        shuffle(words)
        s = ""
        while words:
            s += words.pop() + "".join(choice("-,.?!_:;/ ") for _ in range(randint(1, 5)))
        return s
    
    @test.it("Tests")
    def it_1():
        for _ in range(100): check(gen_string())

The solution using Python

Option 1:

The SongDecoder Dubstep Challenge with Java

Sat, 15 Aug 2020 02:50:17 +0000

The challenge

Polycarpus works as a DJ in the best Berland nightclub, and he often uses dubstep music in his performance. Recently, he has decided to take a couple of old songs and make dubstep remixes from them.

Let’s assume that a song consists of some number of words (that don’t contain WUB). To make the dubstep remix of this song, Polycarpus inserts a certain number of words “WUB” before the first word of the song (the number may be zero), after the last word (the number may be zero), and between words (at least one between any pair of neighbouring words), and then the boy glues together all the words, including “WUB”, in one string and plays the song at the club.

Break camelCase Challenge in Java

Fri, 14 Aug 2020 07:34:02 +0000

The challenge

Complete the solution so that the function will break up camel casing, using a space between words.

Example

solution("camelCasing")  ==  "camel Casing"

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void tests() {
      assertEquals( "Incorrect", "camel Casing", Solution.camelCase("camelCasing"));
      assertEquals( "Incorrect", "camel Casing Test", Solution.camelCase("camelCasingTest"));
      assertEquals( "Incorrect", "camelcasingtest", Solution.camelCase("camelcasingtest"));
    }
}

The solution in Java

class Solution {
  public static String camelCase(String input) {
    String out = "";
    
    for (int i=0; i<input.length(); i++) {
      String c = Character.toString(input.charAt(i));
      if (c.equals(c.toUpperCase())) {
        out+=" ";
      }
      out+=c;
    }
    
    return out;
  }
}

Sort Binary Tree by Levels using Python

Thu, 13 Aug 2020 00:14:32 +0000

The challenge

You are given a binary tree:

class Node:
    def __init__(self, L, R, n):
        self.left = L
        self.right = R
        self.value = n

Your task is to return the list with elements from tree sorted by levels, which means the root element goes first, then root children (from left to right) are second and third, and so on.

Return empty list if root is None.

Example 1 – following tree:

How to Split a String with Python

Wed, 12 Aug 2020 08:26:31 +0000

Splitting a string in Python is really easy.

You simply take a string and apply the split() method.

"Your String".split()

See some examples of the Python Split String method:

A Python Split String – Example

# Your string
a_string = "This is our string"

# Split into a list
a_list = a_string.split()

# Print the list
print(a_list)

Python Split String – Syntax

string.split(separator, maxsplit)

Parameter Values


Parameter	Description
separator	Optional – What to split the string on. The default is the whitespace character
maxsplit	Optional – How many splits to perform. The default is -1, meaning “no limit”

Some examples for Python Split String

Use a comma (,) as the separator:

How to fix the Terraform stuck on “Refreshing state…” problem

Tue, 11 Aug 2020 00:24:18 +0000

Terraform is a fantastic tool to help automate your infrastructure as code.

Quite a few times however, I have noticed a few strange issues, one of them is when Terraform gets stuck while refreshing the state.

This can happen when running terraform plan or in-fact, when running a range of other commands that require the state-file to be refreshed and used.

The problem

Terraform gets stuck on this message:

Refreshing Terraform state in-memory prior to plan…

The “Split Strings” Challenge using Java

Mon, 10 Aug 2020 07:41:20 +0000

The challenge

Complete the solution so that it splits the string into pairs of two characters. If the string contains an odd number of characters then it should replace the missing second character of the final pair with an underscore (‘_’).

Examples:

StringSplit.solution("abc") // should return {"ab", "c_"}
StringSplit.solution("abcdef") // should return {"ab", "cd", "ef"}

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.Arrays;

public class SampleTest {
    @Test
    public void testEvenString() {
       String s = "abcdef";
       String s1 = "HelloWorld";
       assertEquals("Should handle even string","[ab, cd, ef]", Arrays.toString(StringSplit.solution(s)));
       assertEquals("Should handle even string","[He, ll, oW, or, ld]", Arrays.toString(StringSplit.solution(s1)));
    }
    
    @Test
    public void testOddString() {
       String s = "abcde";
       String s1 = "LovePizza";
       assertEquals("Should handle odd string","[ab, cd, e_]", Arrays.toString(StringSplit.solution(s)));
       assertEquals("Should handle odd string","[Lo, ve, Pi, zz, a_]", Arrays.toString(StringSplit.solution(s1)));
    }
  
  
    @Test
    public void testEmptyString() {
       String s = "";
       assertEquals("Should handle empty string","[]", Arrays.toString(StringSplit.solution(s)));
    }
}

The solution in Java

public class StringSplit {
    public static String[] solution(String s) {
      
        // if it's blank, then return
        if (s.length()==0) return new String[0];
      
        // if not even, then add an underscore to the end
        if (s.length()%2!=0) {
          s+="_";
        }
      
        // determine the space needed for the return array
        int spaceNeeded = s.length()/2;
        
        // create a new array to populate and return
        String[] out = new String[spaceNeeded];
      
        // create an builder index
        int j = 0;
      
        // loop through the input string
        for (int i=0; i<s.length(); i++) {
          
          // create a new string to build
          StringBuilder sb = new StringBuilder();
          // add the current item
          sb.append(s.charAt(i));
          // add the next item
          sb.append(s.charAt(i+1));
          
          // populate our output string as we go
          out[j] = sb.toString();
          
          // increment both counters
          i++;
          j++;
        }
      
        // return the built string
        return out;
    }
}

A simple alternative using regular expressions:

Converting to PigLatin with Python

Sun, 09 Aug 2020 02:07:52 +0000

The challenge

Move the first letter of each word to the end of it, then add “ay” to the end of the word. Leave punctuation marks untouched. This string manipulation challenge is similar to other Python exercises like counting smiley faces or finding the intersection of two arrays.

Examples

pig_it('Pig latin is cool') # igPay atinlay siay oolcay
pig_it('Hello world !')     # elloHay orldway !

Test cases

Test.assert_equals(pig_it('Pig latin is cool'),'igPay atinlay siay oolcay')
Test.assert_equals(pig_it('This is my string'),'hisTay siay ymay tringsay')

How to write the code in Python

def pig_it(text):
    words = text.split(" ")
    
    new_words = []
    
    for word in words:
        if word.isalpha():
            new_word = word[1:] + word[0] + "ay"
            new_words.append(new_word)
        else:
            new_words.append(word)
        
        
    return " ".join(new_words)

Solving the “Double Cola” Challenge using Java

Sat, 08 Aug 2020 02:30:24 +0000

The challenge

Sheldon, Leonard, Penny, Rajesh and Howard are in the queue for a “Double Cola” drink vending machine; there are no other people in the queue. The first one in the queue (Sheldon) buys a can, drinks it and doubles! The resulting two Sheldons go to the end of the queue. Then the next in the queue (Leonard) buys a can, drinks it and gets to the end of the queue as two Leonards, and so on.

Convert Seconds to Human Readable Time (HH:MM:SS) using Java

Fri, 07 Aug 2020 09:12:47 +0000

The challenge

Write a function, which takes a non-negative integer (seconds) as input and returns the time in a human-readable format (HH:MM:SS)

HH = hours, padded to 2 digits, range: 00 – 99
MM = minutes, padded to 2 digits, range: 00 – 59
SS = seconds, padded to 2 digits, range: 00 – 59

The maximum time never exceeds 359999 (99:59:59)

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class ExampleTest {
  @Test
  public void Tests() {
    assertEquals("makeReadable(0)", "00:00:00", HumanReadableTime.makeReadable(0));
    assertEquals("makeReadable(5)", "00:00:05", HumanReadableTime.makeReadable(5));
    assertEquals("makeReadable(60)", "00:01:00", HumanReadableTime.makeReadable(60));
    assertEquals("makeReadable(86399)", "23:59:59", HumanReadableTime.makeReadable(86399));
    assertEquals("makeReadable(359999)", "99:59:59", HumanReadableTime.makeReadable(359999));
  }
}

The solution in Java

public class HumanReadableTime {
  public static String makeReadable(int seconds) {
    
    return String.format("%02d:%02d:%02d", seconds / 3600, (seconds % 3600) / 60, (seconds % 60));
    
  }
}

Solving the “Mexican Wave” Challenge using Java

Thu, 06 Aug 2020 01:10:47 +0000

The challenge

Task

Your task is to create a function that turns a string into a Mexican Wave. You will be passed a string and you must return that string in an array where an uppercase letter is a person standing up.

Rules

1. The input string will always be lowercase but may be empty.
2. If the character in the string is whitespace then pass over it as if it was an empty seat.

Multiples of 3 and 5 with Python

Wed, 05 Aug 2020 08:02:18 +0000

The challenge

This multiples of 3 and multiples of 5 challenge is a variation of the common FizzBuzz question.

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Finish the solution so that it returns the sum of all the multiples of 3 or 5 below the number passed in. This challenge requires similar modulo operations as seen in how to divide a number in Python.

Solving the “Catching Car Mileage Numbers” Challenge using Python

Tue, 04 Aug 2020 01:08:39 +0000

The challenge

Let’s make it so Bob never misses another interesting number. We’ve hacked into his car’s computer, and we have a box hooked up that reads mileage numbers. We’ve got a box glued to his dash that lights up yellow or green depending on whether it receives a 1 or a 2 (respectively).

It’s up to you, intrepid warrior, to glue the parts together. Write the function that parses the mileage number input, and returns a 2 if the number is “interesting” (see below), a 1 if an interesting number occurs within the next two miles, or a `` if the number is not interesting.

Counting smiley faces with Python

Mon, 03 Aug 2020 08:08:47 +0000

The challenge

Given an array (arr) as an argument complete the function countSmileys that should return the total number of smiling faces.

Rules for a smiling face:

Each smiley face must contain a valid pair of eyes. Eyes can be marked as : or ;
A smiley face can have a nose but it does not have to. Valid characters for a nose are - or ~
Every smiling face must have a smiling mouth that should be marked with either ) or D

No additional characters are allowed except for those mentioned.

Convert String to Camel Case using Java

Sun, 02 Aug 2020 02:00:56 +0000

The challenge

Complete the method/function so that it converts dash/underscore delimited words into camel casing. The first word within the output should be capitalized only if the original word was capitalized (known as Upper Camel Case, also often referred to as Pascal case).

Examples

toCamelCase("the-stealth-warrior"); // returns "theStealthWarrior"

toCamelCase("The_Stealth_Warrior"); // returns "TheStealthWarrior"

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void testSomeUnderscoreLowerStart() {
      String input = "the_Stealth_Warrior";
      System.out.println("input: "+input);      
      assertEquals("theStealthWarrior", Solution.toCamelCase(input));
    }
    @Test
    public void testSomeDashLowerStart() {
      String input = "the-Stealth-Warrior";
      System.out.println("input: "+input);      
      assertEquals("theStealthWarrior", Solution.toCamelCase(input));
    }
}

The solution in Java

import java.lang.StringBuilder;
class Solution{

  // Our method
  static String toCamelCase(String s){

    // create a StringBuilder to create our output string
    StringBuilder sb = new StringBuilder();
    
    // determine when the next capital letter will be
    Boolean nextCapital = false;

    // loop through the string
    for (int i=0; i<s.length(); i++) {

      // if the current character is a letter
      if (Character.isLetter(s.charAt(i))) {

        // get the current character
        char tmp = s.charAt(i);

        // make it a capital if required
        if (nextCapital) tmp = Character.toUpperCase(tmp);

        // add it to our output string
        sb.append(tmp);

        // make sure the next character isn't a capital
        nextCapital = false;

      } else {
        // otherwise the next letter should be a capital
        nextCapital = true;
      }
    }
    
    // return our output string
    return sb.toString();
  }
}

How to Setup an SSH Server on AWS

Sat, 01 Aug 2020 09:25:48 +0000

Basic instructions on how to set up an SSH server on an Ubuntu 16.04/18.04 EC2 instance.

Step 1 – Create a New User

sudo adduser testuser

Step 2 – Create a Directory for File Transfers

sudo mkdir -p /var/sftp/uploads
sudo chown root:root /var/sftp
sudo chmod 755 /var/sftp
sudo chown testuser:testuser /var/sftp/uploads

Step 3 – Restrict Access to One Directory

Open the SSH server configuration file

sudo nano /etc/ssh/sshd_config

Add the following to the bottom of the file:

How to Convert Numeric Words into Numbers using Python

Fri, 31 Jul 2020 01:31:08 +0000

Challenge

Using Python, we want to convert words into numbers. In this challenge, we will explore how to convert a string into an integer.

The strings simply represent the numbers in words. Let’s convert these words into numbers.

Examples:

“one” => 1
“twenty” => 20
“two hundred forty-six” => 246
“seven hundred eighty-three thousand nine hundred and nineteen” => 783919

Additional Notes:

The minimum number is “zero” (inclusively)
The maximum number, which must be supported is 1 million (inclusively)
The “and” in e.g. “one hundred and twenty-four” is optional, in some cases it’s present and in others, it’s not
All tested numbers are valid, you don’t need to validate them

Test cases to convert words into numbers

Test.assert_equals(parse_int('one'), 1)
Test.assert_equals(parse_int('twenty'), 20)
Test.assert_equals(parse_int('two hundred forty-six'), 246)

The solution in Python to convert words into numbers

def parse_int(textnum, numwords={}):
    # create our default word-lists
    if not numwords:

      # singles
      units = [
        "zero", "one", "two", "three", "four", "five", "six", "seven", "eight",
        "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
        "sixteen", "seventeen", "eighteen", "nineteen",
      ]

      # tens
      tens = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]

      # larger scales
      scales = ["hundred", "thousand", "million", "billion", "trillion"]

      # divisors
      numwords["and"] = (1, 0)

      # perform our loops and start the swap
      for idx, word in enumerate(units):    numwords[word] = (1, idx)
      for idx, word in enumerate(tens):     numwords[word] = (1, idx * 10)
      for idx, word in enumerate(scales):   numwords[word] = (10 ** (idx * 3 or 2), 0)

    # primary loop
    current = result = 0
    # loop while splitting to break into individual words
    for word in textnum.replace("-"," ").split():
        # if problem then fail-safe
        if word not in numwords:
          raise Exception("Illegal word: " + word)

        # use the index by the multiplier
        scale, increment = numwords[word]
        current = current * scale + increment
        
        # if larger than 100 then push for a round 2
        if scale > 100:
            result += current
            current = 0

    # return the result plus the current
    return result + current

Solve The Triangle of Odd Numbers using Python

Thu, 30 Jul 2020 08:13:12 +0000

The challenge

Given the triangle of consecutive odd numbers:

             1
          3     5
       7     9    11
   13    15    17    19
21    23    25    27    29
...

Calculate the row sums of this triangle from the row index (starting at index 1) e.g.:

row_sum_odd_numbers(1); # 1
row_sum_odd_numbers(2); # 3 + 5 = 8

Test cases

Test.assert_equals(row_sum_odd_numbers(1), 1)
Test.assert_equals(row_sum_odd_numbers(2), 8)
Test.assert_equals(row_sum_odd_numbers(13), 2197)
Test.assert_equals(row_sum_odd_numbers(19), 6859)
Test.assert_equals(row_sum_odd_numbers(41), 68921)

The solution in code

While there are many ways to achieve this, the absolute most simple is to realise that the solution is just a n^3.

“Who likes it” code Challenge in Python

Wed, 29 Jul 2020 08:43:02 +0000

The Challenge

You probably know the “like” system from Facebook and other pages. People can “like” blog posts, pictures or other items. We want to create the text that should be displayed next to such an item.

Implement a function likes :: [String] -> String, which must take in input array, containing the names of people who like an item. It must return the display text as shown in the examples:

Python 4 New Features Planned

Tue, 28 Jul 2020 01:24:52 +0000

It took the Python community a long time to move from Python 2 to Python 3. Now as we approach the possible end of Python 3 version history, we are approaching a potential Python 4.

What to expect in Python 4

Other than Python version 4 being mentioned in the PEP documentation, there is currently no formal writeup of the Python 4 feature-set.

Therefore we have to either believe that it will be the next version after 3.9, and will simply become 3.10. Otherwise it will fall back to version 4.

Custom RGB To Hex Conversion with Python

Mon, 27 Jul 2020 01:06:46 +0000

The challenge

Note: Your answer should always be 6 characters long, the shorthand with 3 will not work here.

The following are examples of expected output values:

Sort a Java Integer in Descending Order

Sun, 26 Jul 2020 02:55:42 +0000

The challenge

Your task is to make a function that can take any non-negative integer as an argument and return it with its digits in descending order. Essentially, rearrange the digits to create the highest possible number.

Examples:

Input: 42145 Output: 54421

Input: 145263 Output: 654321

Input: 123456789 Output: 987654321

Test cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class DescendingOrderTest {

    @Test
    public void test_01() {
        assertEquals(0, DescendingOrder.sortDesc(0));
    }    

    @Test
    public void test_02() {
        assertEquals(51, DescendingOrder.sortDesc(15));
    }
    
    @Test
    public void test_03() {
        assertEquals(987654321, DescendingOrder.sortDesc(123456789));
    }
}

The solution in Java

public class DescendingOrder {
  public static int sortDesc(final int num) {
    
    // return if a negative number
    if (num<0) return num;
    
    // our number we will return
    int sortedNumber = 0;
    
    // loop with a maximum number int
    // perform loop in reverse
    for (int i = 9; i >= 0; i--) {
        // set a local number variable
        int tmpNumber = num;
        // while greater than 0
        while (tmpNumber > 0) {
            // get the digit
            int digit = tmpNumber % 10;
            // check for the greatest digit in the given number
            if (digit == i) {
                // build the sortedNumber value
                sortedNumber *= 10;
                sortedNumber += digit;
            }
            // reduce the loop variable
            tmpNumber /= 10;
        }
    }
    // return our sorted number
    return sortedNumber;
  }
}

Get the Sum of Digits / Digital Root using Java

Sat, 25 Jul 2020 00:40:19 +0000

The challenge

Digital root is the recursive sum of all the digits in a number.

Given n, take the sum of the digits of n. If that value has more than one digit, continue reducing in this way until a single-digit number is produced. This is only applicable to the natural numbers.

Examples

    16  -->  1 + 6 = 7
   942  -->  9 + 4 + 2 = 15  -->  1 + 5 = 6
132189  -->  1 + 3 + 2 + 1 + 8 + 9 = 24  -->  2 + 4 = 6
493193  -->  4 + 9 + 3 + 1 + 9 + 3 = 29  -->  2 + 9 = 11  -->  1 + 1 = 2

Tests cases

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class DRootExampleTest {
    @Test
    public void Tests() {
      assertEquals( "Nope!" , 7, DRoot.digital_root(16));
      assertEquals( "Nope!" , 6, DRoot.digital_root(456));
    }
}

The solution in Java

public class DRoot {
  public static int digital_root(int n) {
    
    // return the number if less than 10
    // this is to break out of the recursion loop
    if (n<10) return n;
    
    // set an output variable
    int out = 0;
    
    // while we still have numbers, loop
    while(n>0) {
      // increment our output by the base
      out += n % 10;
      // reduce the base by the same amount
      n = n / 10;
    }
  
    // return a recursion of the output
    return digital_root(out);
  }
}

How to write a Chain Adding Function in Python

Fri, 24 Jul 2020 01:00:20 +0000

The challenge

We want to create a function that will add numbers together when called in succession.

add(1)(2);
# returns 3

We also want to be able to continue to add numbers to our chain.

add(1)(2)(3) # 6
add(1)(2)(3)(4) # 10
add(1)(2)(3)(4)(5) # 15

and so on.

A single call should return the number passed in.

add(1); # 1

We should be able to store the returned values and reuse them.

addTwo = add(2)
addTwo # 2
addTwo + 5 # 7
addTwo(3) # 5
addTwo(3)(5) # 10

We can assume any number being passed in will be valid whole number.

Get the next biggest number with the same digits using Python

Thu, 23 Jul 2020 01:38:03 +0000

The challenge

Create a function that takes a positive integer and returns the next bigger number that can be formed by rearranging its digits. For example:

12 ==> 21
513 ==> 531
2017 ==> 2071

nextBigger(num: 12)   # returns 21
nextBigger(num: 513)  # returns 531
nextBigger(num: 2017) # returns 2071

If the digits can’t be rearranged to form a bigger number, return -1 (or nil in Swift):

9 ==> -1
111 ==> -1
531 ==> -1

nextBigger(num: 9)   # returns nil
nextBigger(num: 111) # returns nil
nextBigger(num: 531) # returns nil

Test cases

Test.assert_equals(next_bigger(12),21)
Test.assert_equals(next_bigger(513),531)
Test.assert_equals(next_bigger(2017),2071)
Test.assert_equals(next_bigger(414),441)
Test.assert_equals(next_bigger(144),414)

The solution in Python

This problem requires careful manipulation of digits and arrays, similar to other Python challenges like finding the intersection of two arrays or getting the last element of a list.

Solving Tribonacci Sequence with Python

Wed, 22 Jul 2020 00:48:13 +0000

The challenge

As the name may already reveal, it works basically like a Fibonacci, but summing the last 3 (instead of 2) numbers of the sequence to generate the next.

So, if we are to start our Tribonacci sequence with [1, 1, 1] as a starting input (AKA signature), we have this sequence:

[1, 1 ,1, 3, 5, 9, 17, 31, ...]

But what if we started with [0, 0, 1] as a signature? As starting with [0, 1] instead of [1, 1] basically shifts the common Fibonacci sequence by once place, you may be tempted to think that we would get the same sequence shifted by 2 places, but that is not the case and we would get:

The Casino Chips Problem Solved with Python

Tue, 21 Jul 2020 10:46:55 +0000

The challenge

You are given three piles of casino chips: white, green and black chips:

the first pile contains only white chips
the second pile contains only green chips
the third pile contains only black chips

Each day you take exactly two chips of different colors and head to the casino. You can chose any color, but you are not allowed to take two chips of the same color in a day.

Check if Isogram using Python

Mon, 20 Jul 2020 08:20:00 +0000

The challenge

An isogram is a word that has no repeating letters, consecutive or non-consecutive. Implement a function that determines whether a string that contains only letters is an isogram. Assume the empty string is an isogram. Ignore letter case.

is_isogram("Dermatoglyphics" ) == true
is_isogram("aba" ) == false
is_isogram("moOse" ) == false # -- ignore letter case

Test cases

Test.assert_equals(is_isogram("Dermatoglyphics"), True )
Test.assert_equals(is_isogram("isogram"), True )
Test.assert_equals(is_isogram("aba"), False, "same chars may not be adjacent" )
Test.assert_equals(is_isogram("moOse"), False, "same chars may not be same case" )
Test.assert_equals(is_isogram("isIsogram"), False )
Test.assert_equals(is_isogram(""), True, "an empty string is a valid isogram" )

The solution in Python

First pass, using a dictionary (dict):

Find the Longest Common Prefix using Python

Sun, 19 Jul 2020 11:33:31 +0000

The challenge

Write a function to find the longest common prefix string amongst an array of strings. This string manipulation challenge requires careful handling of arrays, similar to getting the last element of a list in Python.

If there is no common prefix, return an empty string "". For more Python string challenges, you might also be interested in converting to PigLatin.

Example 1:

Example 2:

Count and Say with Python

Sat, 18 Jul 2020 13:29:25 +0000

The challenge

he count-and-say sequence is the sequence of integers with the first five terms as following:

1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.

Given an integer n where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence. You can do so recursively, in other words from the previous member read off the digits, counting the number of digits in groups of the same digit.

The Plus One problem solved with Python

Fri, 17 Jul 2020 01:42:40 +0000

The challenge

Given a non-empty array of digits representing a non-negative integer, increment one to the integer. This challenge involves array manipulation similar to finding the intersection of two arrays.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contains a single digit. For more Python array challenges, you might also be interested in getting the last element of a list.

Solving the Single Number problem in Python

Thu, 16 Jul 2020 10:48:05 +0000

The challenge

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

Example 2:

The solution in Python

def singleNumber(nums):
    # create a dictionary/hashmap
    found = {}

    # loop through the nums
    for i in nums:
        # add to map if not found
        if i not in found:
            found[i] = i
        else:
            # otherwise remove it
            del found[i]

    # loop through the found map and return the first item
    for i in found:
        return i

Rotate a Matrix List in Python

Wed, 15 Jul 2020 10:13:19 +0000

The challenge

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Example 2:

Check if Valid Sudoku Blocks in Java

Tue, 14 Jul 2020 09:10:02 +0000

The challenge of solving valid Sudoku blocks

Determine if a 9×9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Each row must contain the digits 1-9 without repetition.
Each column must contain the digits 1-9 without repetition.
Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

(A partially filled sudoku which is valid.)

Find the Intersection of Two Arrays in Python

Mon, 13 Jul 2020 09:21:27 +0000

The challenge

Given two arrays, write a function to compute their intersection.

Example 1:

Example 2:

Note:

Each element in the result should appear as many times as it shows in both arrays.
The result can be in any order.

This is a common array manipulation problem that’s similar to other Python challenges like counting smiley faces or getting the next biggest number with the same digits.

Rotate an Array K Times in Python

Sun, 12 Jul 2020 13:58:50 +0000

The challenge

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Example 2:

Constraints:

1 <= nums.length <= 2 * 10^4
It’s guaranteed that nums[i] fits in a 32 bit-signed integer.
k >= 0

The solution in Python

Option 1 could be as follows:

FizzBuzz in Java

Sat, 11 Jul 2020 00:07:41 +0000

The challenge

Write a program that outputs the string representation of numbers from 1 to n.

But for multiples of three it should output “Fizz” instead of the number and for the multiples of five output “Buzz”. For numbers which are multiples of both three and five output “FizzBuzz”.

Example:

The solution in Java

class Solution {
    public List<String> fizzBuzz(int n) {
        List<String> l = new ArrayList<>();
        
        for (int i=1; i<=n; i++) {
            if (i%3==0 && i%5==0) {
              l.add("FizzBuzz");  
            } else if (i%3==0) {
                l.add("Fizz");
            } else if (i%5==0) {
                l.add("Buzz");
            } else {
                l.add(""+i);
            }
        }
        
        return l;
    }
}

Python Splices reimplemented in Java

Fri, 10 Jul 2020 10:58:26 +0000

Python has a fantastic feature called slices. It allows you to work with a list, set or string by it’s index items.

E.g.:

string_sample = "hello world"

string_sample[:-1]
>>> "hello worl"

string_sample[-1]
>>> "d"

string_sample[3]
>>> "l"

You can also do things like:

string_sample[3:5]
>>> 'lo'

Or even in reverse!

string_sample[::-1]
>>> 'dlrow olleh'

A possible Java implementation

public String slice_start(String s, int startIndex) {
    if (startIndex < 0) startIndex = s.length() + startIndex;
    return s.substring(startIndex);
}

public String slice_end(String s, int endIndex) {
    if (endIndex < 0) endIndex = s.length() + endIndex;
    return s.substring(0, endIndex);
}

public String slice_range(String s, int startIndex, int endIndex) {
    if (startIndex < 0) startIndex = s.length() + startIndex;
    if (endIndex < 0) endIndex = s.length() + endIndex;
    return s.substring(startIndex, endIndex);
}

Solving Two Sum in Python

Thu, 09 Jul 2020 10:47:06 +0000

The challenge

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

The solution in Python

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        # keep a hashmap of items found
        seen = {}
        
        # loop through the nums, with int and value
        for i, v in enumerate(nums):
            # set remaining to the target minus the value
            remaining = target - v
            # check if the new value is in the hashmap
            if remaining in seen:
                # return it and the index
                return [seen[remaining], i]
            # otherwise, put it on the map instead
            seen[v] = i
        
        # nothing found, return an empty list
        return []

Get the Next Small Integer in Python

Wed, 08 Jul 2020 08:58:37 +0000

The challenge

Write a function:

def solution(A)

that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.

For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.

Given A = [1, 2, 3], the function should return 4.

Given A = [−1, −3], the function should return 1.

Write an efficient algorithm for the following assumptions:

Is a Valid Palindrome with Java

Tue, 07 Jul 2020 09:54:10 +0000

The challenge

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Example 2:

Constraints:

s consists only of printable ASCII characters.

The solution in Java

class Solution {
    // take in a String
    public boolean isPalindrome(String s) {
        
        // remove all non-alphanumeric characters and lowercase everything
        s = s.replaceAll("\\P{Alnum}", "").toLowerCase();
        
        // loop through the String
        for (int i=0; i<s.length(); i++) {
            // if the beginning and last characters don't match, return false
            // also walk in both directions and do the same
            if (s.charAt(i)!=s.charAt(s.length()-i-1))
                return false;
        }
        
        // return true if we get here
        return true;
    }
}

Is a Valid Anagram with Java

Mon, 06 Jul 2020 11:15:24 +0000

The challenge

Given two strings s and t , write a function to determine if t is an anagram of s.

Example 1:

Example 2:

Note:
You may assume the string contains only lowercase alphabets.

Follow up:
What if the inputs contain Unicode characters? How would you adapt your solution to such a case?

How to ReImplement strStr() in Java

Sun, 05 Jul 2020 11:12:40 +0000

What we want to achieve

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Example 1:

Example 2:

How to code this

class Solution {
    public int strStr(String haystack, String needle) {
        // If needle is an empty string
        if (needle.isEmpty()) return 0;

        // If the needle is not within the haystack
        if (!haystack.contains(needle)) return -1;

        // declare an index and the needle's length
        int index = 0;
        int len = needle.length();
        
        // loop through the hackstack minus the needle's length
        for (int i = 0; i <= haystack.length() - len; i++) {
            // compare the needle with the hackstack new string
            // created from using substring, start->end
            if (haystack.substring(i, i + len).equals(needle)) {
                // set the index and exit
                index = i;
                break;
            }
        }
        return index;
    }
}

Third Maximum Number with Java

Sat, 04 Jul 2020 13:50:39 +0000

The challenge

Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).

Example 1:

Example 2:

Example 3:

The solution

I have seen many possible resolutions to this problem, but my favourite has to be the following:

How to Quickly Hide all Icons on a Mac’s Desktop

Fri, 03 Jul 2020 09:18:04 +0000

Why the need to hide icons?

Perhaps you have a screen-share session coming up and you want a nice clean desktop to show everyone. Also, nobody will see all your funny files and folders as they wait for you.

Just open the Terminal and enter the following to hide all icons:

If you’re not familiar with the Terminal; it is a Mac application that allows you to enter commands like the ones below, to enable and disable advanced features, among other things.

First Unique Character in a String using Java

Thu, 02 Jul 2020 02:04:22 +0000

The challenge

Given a string, find the first non-repeating character in it and return its index. If it doesn’t exist, return -1.

Examples:

Note: You may assume the string contains only lowercase English letters.

The solution

class Solution {
    // take in a String and return an int containing the index
    public int firstUniqChar(String s) {
        // create a HashMap to hold our counts
        HashMap<Character, Integer> h = new HashMap<>();
        // get the string's length
        int len = s.length();
        
        // loop to populate the HashMap
        for(int i=0; i<len; i++) {
            // get the Character
            char c = s.charAt(i);
            // add or update HashMap entry
            h.put(c, h.getOrDefault(c, 0)+1);
        }
        
        // loop to look for non-duplicates
        for(int i=0; i<len; i++) {
            // get the Character
            char c = s.charAt(i);
            // if only have 1 item, then we found our match
            if (h.get(c)==1)
                return i;
        }
        
        // return -1 if all else fails
        return -1;
        
    }
}

How to fix the Release Version 5 Not Supported error in IntelliJ

Wed, 01 Jul 2020 01:19:11 +0000

What do you do when you create a new Maven Java project, and when you run it, you get the following error:

Error:java: error: release version 5 not supported

Sometimes the error could also read as follows:

java: Source option 5 is no longer supported. Use 6 or later.

Luckily for us, the solution is exactly the same!

Solution

Open the project’s pom.xml file and add the following snippet:

<properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
</properties>

Now open the Maven side-panel, and click the Report All Maven Projects button.

Facebook’s custom IPv6 range

Tue, 30 Jun 2020 10:51:21 +0000

I noticed an interesting thing with a certain visitor after posting a blog post to Facebook.

The IP address that the Facebook crawler uses to visit the site on callback to get meta-data has a custom IPv6 sub-range.

IPv6: 2a03:2880:ff:1a::face:b00c
Host: fwdproxy-prn-026.fbsv.net

Notice 2a03:2880:ff:1a::face:b00c

How this is done

The IPv4 addresses could only use regular integers (decimal); numbers between 0 and 9.

However, IPv6 can use any and all hexadecimal; 0-9 and a-f.

How to Reverse an Integer in Java

Mon, 29 Jun 2020 01:02:18 +0000

The challenge

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Example 2:

Example 3:

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Reverse a String in-place using Java

Sun, 28 Jun 2020 11:02:37 +0000

The challenge

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Example 1:

Check if a Java array Contains Duplicates

Sat, 27 Jun 2020 10:03:55 +0000

The challenge

Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

Example 2:

Example 3:

The solution

class Solution {
    // return a boolean from the primitive int array input
    public boolean containsDuplicate(int[] nums) {
        // create a HashMap to hold our values
        HashMap<Integer, Integer> hm = new HashMap<>();
        
        // loop through the input array
        for (int i=0; i<nums.length; i++) {
            // return true if we have seen a duplicate
            // otherwise add the int to the HashMap
            if (hm.get(nums[i])!=null) return true;
            else hm.put(nums[i], 1);
        }
        
        // return false if all else fails
        return false;
    }
}

Find All Numbers Disappeared in an Array using Python

Fri, 26 Jun 2020 08:28:36 +0000

The challenge

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Find all the elements of [1, n] inclusive that do not appear in this array.

Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.

Example:

The solution

class Solution:
    # our method
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        # get the length / amount of items
        l=len(nums)
        # create a `set` to remove duplicates
        nums=set(nums)
        # create a new array to return
        d=[]

        # loop through the amount of items in the input array
        for i in range(1,l+1):
            # if the item is not in the input list
            if i not in nums:
                # add it to the return list
                d.append(i)

        # return the new array
        return d

The Array Height Checker Problem in Java

Thu, 25 Jun 2020 08:06:10 +0000

The challenge

Students are asked to stand in non-decreasing order of heights for an annual photo.

Return the minimum number of students that must move in order for all students to be standing in non-decreasing order of height.

Notice that when a group of students is selected they can reorder in any possible way between themselves and the non selected students remain on their seats.

Example 1:

Example 2:

Find the Squares of a Sorted Array in Java

Wed, 24 Jun 2020 09:06:03 +0000

The challenge

Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order.

Example 1:

Example 2:

Note:

1 <= A.length <= 10000
-10000 <= A[i] <= 10000
A is sorted in non-decreasing order.

The solution

class Solution {
    // return the sorted array squared
    public int[] sortedSquares(int[] A) {
        // create a new primitive int array
        int[] res = new int[A.length];
        // loop through the input array
        for (int i=0; i<A.length; i++) {
            // square each value
            res[i] = A[i] * A[i];
        }
        
        // finally sort the array
        Arrays.sort(res);
        
        // return the array
        return res;
    }
}

Sorting a Java Array by Parity

Tue, 23 Jun 2020 09:49:30 +0000

The challenge

Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A.

You may return any answer array that satisfies this condition.

Example 1:

Note:

1 <= A.length <= 5000
0 <= A[i] <= 5000

The solution

class Solution {
    // return a sorted primitive int array
    public int[] sortArrayByParity(int[] A) {
        
        // keep track of place
        int lastIndex = 0;
        
        // loop through input array
        for (int i=0; i<A.length; i++) {
            // if we found an even number
            if (A[i]%2==0) {
                // keep track of the values
                int lastValue = A[lastIndex];
                int thisValue = A[i];
                
                // swap the values
                A[i] = lastValue;
                A[lastIndex] = thisValue;
                
                // increment our swap index
                lastIndex++;
            }
        }
        
        // return a sorted array
        return A;
    }
}

Remove Duplicates from Sorted Array in Java

Mon, 22 Jun 2020 13:20:45 +0000

Say you have an array of primitive integers and you want to remove all duplicates.

You can find out how many non-duplicate integers are in the array with this method:

class Solution {
    public int removeDuplicates(int[] nums) {
        
        if (nums.length == 0) return 0;
        int i = 0;
        for (int j = 1; j < nums.length; j++) {
            if (nums[j] != nums[i]) {
                i++;
                nums[i] = nums[j];
            }
        }
        return i + 1;
    }
}

Because we pass the nums array in as a reference, and modify the variable in-place with no additional space, you could just continue using it as is.

Replace Elements with Greatest Element on Right Side using Java

Sun, 21 Jun 2020 00:03:32 +0000

The challenge

Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.

After doing so, return the array.

Example 1:

Constraints:

1 <= arr.length <= 10^4
1 <= arr[i] <= 10^5

The solution

class Solution {
    public int[] replaceElements(int[] arr) {
        // loop through all array items
        for (int i=0; i<arr.length; i++) {
            
            // if the last item
            if (i==arr.length-1) {
                // set the last item
                arr[i] = -1;
            } else {

                // set a variable to check biggest value against
                int biggest = 0;
                // loop through the internal looperr
                for(int j=i+1; j<arr.length; j++) {
                    // if the next value is bigger than our
                    // current biggest, then update it
                    if (arr[j]>biggest) biggest = arr[j];
                }
                // replace the current value with the biggest found
                arr[i] = biggest;
            }
        }
        // return our array of ints
        return arr;
    }
}

The Valid Mountain Array Problem using Java

Sat, 20 Jun 2020 16:59:16 +0000

Introducing the problem

Given an array A of integers, return true if and only if it is a valid mountain array.

Recall that A is a mountain array if and only if:

A.length >= 3
There exists some i with 0 < i < A.length - 1 such that:
- A[0] < A[1] < ... A[i-1] < A[i]
- A[i] > A[i+1] > ... > A[A.length - 1]

The constraints

Example 1:

HashMaps (aka: Dictionaries) in Python

Fri, 19 Jun 2020 15:35:04 +0000

Introduction

Java has a built-in called HashMap. It allows you to store and very quickly retrieve key value pairs.

In Python, this is called a dictionary and appears very similar to a JSON Object for those familiar with Javascript and similar languages.

Dictionaries as HashMaps

An example of a dictionary in Python is as follows:

ages = {"Bob":25, "James":54, "Darren":44}

The same can be created using the dict keyword:

ages = dict({"Bob":25, "James":54, "Darren":44})

A third way to create and populate this:

Find Numbers with Even Number of Digits using Java

Thu, 18 Jun 2020 14:18:01 +0000

The challenge

Given an array nums of integers, return how many of them contain an even number of digits.

Example 1:

Example 2:

Constraints:

1 <= nums.length <= 500
1 <= nums[i] <= 10^5

The solution

class Solution {
    public int findNumbers(int[] nums) {
        // keep track of the amount to return
        int evens = 0;
        
        // loop through all the nums
        for (int i=0; i<nums.length; i++) {
            
            int digits = 0, num = nums[i];
            // while we divide by 10
            while (num!=0) {
                num /= 10;
                // increment our count
                ++digits;
            }
            
            // increment if even
            if (digits%2==0) evens++;
            
        }
        
        return evens;
    }
}

The Relational Database Model

Wed, 17 Jun 2020 11:28:53 +0000

Relational databases first made an appearance in the mid-1970s, between the years 1974 and 1977 with the creation of Ingres and System R which led to the creation of MS SQL Server, Sybase, Wang?s PACE and Britton-Lee to name a few (Quickbase, n.d.).

It was only until the 1980s that SQL (Structured Query Language) became the standard query language used by relational databases.

How to use a Java HashSet by example

Tue, 16 Jun 2020 12:18:53 +0000

What is a HashSet

A HashSet is an unordered collection containing unique elements. It has the standard collection operations Add, Remove, Contains, but since it uses a hash-based implementation, these operations are O(1)

Learn with a Programming Question

Given an integer array with even length, where different numbers in this array represent different kinds of candies. Each number means one candy of the corresponding kind. You need to distribute these candies equally in number to brother and sister. Return the maximum number of kinds of candies the sister could gain.

Get The Shortest Path in Binary Matrix using Python

Mon, 15 Jun 2020 15:05:48 +0000

The challenge

In an N by N square grid, each cell is either empty (0) or blocked (1).

A clear path from top-left to bottom-right has length k if and only if it is composed of cells C_1, C_2, ..., C_k such that:

Adjacent cells C_i and C_{i+1} are connected 8-directionally (ie., they are different and share an edge or corner)
C_1 is at location (0, 0) (ie. has value grid[0][0])
C_k is at location (N-1, N-1) (ie. has value grid[N-1][N-1])
If C_i is located at (r, c), then grid[r][c] is empty (ie. grid[r][c] == 0).

Return the length of the shortest such clear path from top-left to bottom-right. If such a path does not exist, return -1.

Palindrome Partitioning in Python

Sun, 14 Jun 2020 14:41:15 +0000

The problem

Given a string s, partition s such that every substring of the partition is a palindrome.

Return all possible palindrome partitioning of s.

Example:

The solution

def partition(self, s: str) -> List[List[str]]:
    ret = []
    def isPal(s):
        return s == s[::-1]

    def fn(s, l):
        if not s:
            ret.append(l)
            return
        for i in range(1, len(s)+1):
            if isPal(s[:i]):
                fn(s[i:], l+[s[:i]])
    fn(s, [])
    return ret

Faster alternative to MySQL Delete Table Contents / Truncate

Sat, 13 Jun 2020 09:33:00 +0000

From time to time you might have some rather big tables that you want to delete all the data quickly and start afresh.

You have a few options at this point. The first you?ll probably look at is:

DELETE FROM `table_name`

The benefit of doing this is DELETE provides the ability to Rollback if all hell breaks loose, but it also means that it will take longer because it requires more memory to store all this additional data

Best Time to Buy and Sell Stock with Python

Fri, 12 Jun 2020 12:28:52 +0000

The problem

Say you have an array prices for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).

Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).

IPv4 CIDR Chart

Thu, 11 Jun 2020 00:04:11 +0000

CIDR stands for Classless Inter-Domain Routing and is a method for allocating IP addresses as well as for IP routing.

It was introduced in 1993 by the Internet Engineering Task Force to replace the previous classful network addressing architecture on the internet.

When choosing a CIDR range for your network, the following chart will show you how many maximum IP’s you can have on that network.

For example, /32 will give you 1 usable IP, /24 will give you 256 usable IPs, while /3 will give you 512 million usable IPs.

Recursively Delete Files and Folders and all Contents using PHP

Wed, 10 Jun 2020 10:01:12 +0000

Below is a quick and easy way to recursively delete all files and folders in a given path using PHP.

function destroy_dir($dir) {
  if (!is_dir($dir) || is_link($dir))
    return unlink($dir);

  foreach (scandir($dir) as $file) {
    if ($file == "." || $file == "..")
      continue;
    if (!destroy_dir($dir."/".$file)) {
      chmod($dir."/".$file, 0777);
      if (!destroy_dir($dir."/".$file)) return false;
    }
  }
  return rmdir($dir);
}

destroy_dir("/var/www/site/public_html/directory/");

Product Update: ADD becomes Serengeti

Tue, 09 Jun 2020 10:01:23 +0000

As a product update; The “Autonomous Distributed Database”, otherwise known as simply ADD has been renamed to Serengeti.

The Serengeti is a vast ecosystem in east-central Africa. It spans 12,000 square miles (30,000 square kilometers), according to NASA, giving rise to its name, which is derived from the Maasai language and means “endless plains.” This region of Africa is located in north Tanzania and extends to southwestern Kenya.

Much the same, the Serengeti database project is a truly autonomous distributed system that has no visible ending nor capacity. There is the potential to scale it infinitely, horizontally without downtime or data loss.

SQL to Append all Fields if Shorter than a set Length

Mon, 08 Jun 2020 07:46:31 +0000

This came in very handy for me at one point because I needed to have a certain field in each row 14 characters long, but half of them were only 12 characters long.

In MySQL:

update `table` set `field` = CONCAT(`field`, '1') where LEN(`field`) = 13;

In MSSQL:

update `table` set `field` = CONCAT(`field`, '1') where LENGTH(`field`) = 13;

Validate Email Address in Javascript

Sun, 07 Jun 2020 11:44:03 +0000

Below is a nice little Javascript RegularExpression to validate email addresses.

/^\w.+@[a-zA-Z_.]+?\.[a-zA-Z.]{2,3}$/

..and to use it..

if (/^\w.+@[a-zA-Z_.]+?\.[a-zA-Z.]{2,3}$/.test(email)) alert("Success");
else alert("Fail");

Remove hash from window.location in Javascript

Sat, 06 Jun 2020 12:12:30 +0000

E.g. URL: http://example.com/?option=1&task=2&listing_id=36&layout=4&table=5#some_hash_value_here

So how would you get the current URL using Javascript?

That is really easy, you can use window.location.href or just simply window.location.

But how do you replace the #hash at the end if it exists?

That too is quite easy, you can just do something like this:

window.location.href.split("#")[0]

window.location.href.substr(0, window.location.href.indexOf("#"))

So now that we have the value of the current URL how do we refresh the page with it?

The Benefits and Dangers of Artificial Intelligence

Fri, 05 Jun 2020 13:18:00 +0000

Artificial Intelligence (AI) is usually defined as the science of making computers do things that require intelligence when done by humans. (Jack Copeland, 2000)

Current Benefits of AI

Replicate the decisions and actions of humans without human shortcomings.
Computers don’t get fatigued and tired.
Computers are not biased by emotions.
Tasks are scalable and can be done very quickly and effectively.

Current Dangers of AI

Some decisions require a level of grey area.
Replacing jobs and roles done by humans leading to a higher level of unemployment and poverty.
Viruses and bugs in code leading to catastrophic circumstances such as accidents with self-driving cars and in aviation systems.

There are many trends currently taking place in the field of AI.

The Decoded String at Index using Java

Thu, 04 Jun 2020 11:25:56 +0000

The Challenge

An encoded string S is given. To find and write the decoded string to a tape, the encoded string is read one character at a time and the following steps are taken:

If the character read is a letter, that letter is written onto the tape.
If the character read is a digit (say d), the entire current tape is repeatedly written d-1 more times in total.

Now for some encoded string S, and an index K, find and return the K-th letter (1 indexed) in the decoded string.

Timing Issues in Real-time systems

Wed, 03 Jun 2020 10:05:00 +0000

What are Real-time Systems?

If you look up the term “real-time” in a dictionary, it will tell you that it is the actual time during which a process takes place or an event occurs (Dictionary.com, n.d.).

In computing, it is more often than not due to when an event is created and specific data service is able to respond with the newly updated event in its index.

Find the Minimum Absolute Difference in BST using Java

Tue, 02 Jun 2020 11:35:49 +0000

The question

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.

Example:

Note:

There are at least two nodes in this BST.

The solution

We will start with a stub to build out:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int getMinimumDifference(TreeNode root) {
        
    }
}

Of this, the meat really comes in with the getMinimumDifference method.

Get the Second Highest Salary in MySQL

Mon, 01 Jun 2020 11:43:08 +0000

The problem

Write a SQL query to get the second highest salary from the Employee table.

For example, given the above Employee table, the query should return 200 as the second highest salary. If there is no second highest salary, then the query should return null.

The solution

SELECT DISTINCT
    Salary AS SecondHighestSalary
FROM
    Employee
ORDER BY Salary DESC
LIMIT 1 OFFSET 1

The output

{"headers": ["SecondHighestSalary"], "values": [[200]]}

Find Maximum Subarrays using Java

Sun, 31 May 2020 10:22:07 +0000

The problem

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Example:

The code

// This method takes an array of `ints` and returns an `int`
public int maxSubArray(int[] nums) {
    // Set some `max` variables,
    // ..firstly the minimum `Integer` value
    // ..secondly `0`
    int max = Integer.MIN_VALUE;
    int iMax = 0;

    // Loop through all input `nums`
    for(int num : nums) {
        // increment the `iMax` each loop
        iMax = iMax + num;
        // check if `num` is bigger than `iMax`
        if(iMax < num) {
            // set `iMax` to the `num`
            iMax = num;
        }
        // set the `max` to the max of both our variables
        max = Math.max(max,iMax);
    }
    // return the `max`
    return max;
}

Finding Number Complements using Java

Sat, 30 May 2020 12:03:54 +0000

The problem

Given a positive integer num, output its complement number. The complement strategy is to flip the bits of its binary representation.

Example 1:

Example 2:

Constraints:

The given integer num is guaranteed to fit within the range of a 32-bit signed integer.
num >= 1
You could assume no leading zero bit in the integer’s binary representation.

The code

// Our method that takes in an `int` and returns an `int`
public int findComplement(int num) {
    // Duplicate the input for reference
    int originalNum = num;

    // Set a variable for looping on an index
    long i = 1;
    // Loop while `i` is less or equal to `originalNum`
    while(i<=originalNum) {
        // Shift the variables
        num ^= i;
        i <<= 1;
    }
    // Return the resultant `num`
    return num;
}

Forensic Analysis on Linux (Unix)

Fri, 29 May 2020 09:50:00 +0000

Operating Systems come in a few competing choices, of which the major players are Apple’s MacOS, Microsoft’s Windows and then the various flavours of Linux, of which most are open-sourced while the remainder are proprietary to their vendors.

Of the three, Windows is the most dissimilar, with MacOS and Linux sharing a similar BSD/Unix platform running behind the scenes. This gives MacOS and Linux similar traits when it comes to logging, analysing and tracing system event-logs.

Self Dividing Numbers using Python

Thu, 28 May 2020 09:42:03 +0000

Introduction

A self-dividing number is a number that is divisible by every digit it contains.

For example, 128 is a self-dividing number because 128 % 1 == 0, 128 % 2 == 0, and 128 % 8 == 0.

Also, a self-dividing number is not allowed to contain the digit zero.

Given a lower and upper number bound, output a list of every possible self dividing number, including the bounds if possible.

RuntimeError: thread.init() not called (Python)

Wed, 27 May 2020 09:37:42 +0000

Today I got a really dumb error from Python.

RuntimeError: thread.init() not called

But luckily it’s really easy to fix!

Below is the code before (with the error):

class SomeThread(Thread):
    def __init__(self, myVar):
        self.sMyVar = str(myVar)
    def run(self):
        self.sMyVar = "bla.." + self.sMyVar

And now for the code that resolved the problem:

All About Distributed Databases

Tue, 26 May 2020 11:00:00 +0000

A database “is a structured collection of data. Card indices, printed catalogues of archaeological artefacts and telephone directories are all examples of databases”.

We are going to examine databases that are prevalent in computer systems and go through the core differences between Local and Distributed Databases.

Local

A local database is an isolated database that is stored on a single computer and does not share its data outside of itself or its direct access network.

Network systems security risks

Mon, 25 May 2020 09:28:13 +0000

Networking has played a vital part in the transfer of information as well as the accessibility of information that was never available to previous generations with the rapid increase of internet-connected devices.

Along with the benefits of computing devices being connected to one another for information sharing, online shopping and many other helpful tasks, there is also a real threat present. This is termed under the overarching “Network Security” realm of topics.

Communications and The Software Development Process

Sun, 24 May 2020 20:20:41 +0000

Software Engineering or the Software Development Process is broken down into the following phases.

Requirements
Design
Implementation
Verification
Maintenance

Communication can often breakdown in the system analysis phases. As a knock on effect, the requirements and design can end up not being correctly implemented during the mid to latter stages of software development.

Without correct communication, a software system can end up not meeting the requirements initially laid out by the end client – or whomever requested the system in the first place.

Get the total size of all the files in a directory

Sat, 23 May 2020 19:00:11 +0000

It’s amazing how many times I’ve need to find out the total size of all the files in a directory on one of our servers.

I have grown to love the simplicity of the `du` command.

du -sh

du = Display disk Usage statistics

s tells us to display an entry for each specified file, while h is for “human-readable” output.

This will use the unit suffixes of Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte.

Structured and Object-Oriented Programming

Fri, 22 May 2020 12:30:29 +0000

Software development has really come a long way over the past few decades.

Programming used to always be about doing things in a very procedural way, this means that each line of code is executed in the order that it is written (or placed) in a source code document – we refer to a file where programming code is stored as “source code”.

This is still very much a core basis when writing code, except as software applications have gotten infinitely more expansive and complex, there has been more of a need to reuse sections of code and make it more “modular”.

Moving a MySQL Database without downtime

Thu, 21 May 2020 12:45:00 +0000

At Statvoo Analytics we found ourselves in the position where we needed to move our master MySQL database without ANY downtime and for anyone who’s tried to do this, you will know how hard this can be if it is not done exactly right.

Below I will run through the steps to get the job done efficiently and with no downtime (unless you mess it up that is).

How to use Google Analytics in AngularJS

Wed, 20 May 2020 14:00:21 +0000

It seems to be quite a popular question with not as many answers to hold the weight.

Google Analytics has always been more of a pageviews type tracking use case and up until a few years ago that was all anyone ever really did anyways. However, the web has gotten a lot more complicated with the introduction of javascript and heavy ajax based sites and web applications.

This has caused quite a change in how Analytics Tools are used and how they are expected to gather statistics.

Converting from Legacy to Client-Server or Distributed Systems

Tue, 19 May 2020 12:00:00 +0000

What is a legacy system?

A legacy system is a computing system that has been around for a very long period of time, tends to be difficult to maintain, is prone to issues such as lack of scalability and feature additions, usually centralised in operation and is still heavily utilised in a particular organisation.

What is a client-server / distributed system?

A distributed system is a decentralised networked cluster of computers (servers) that are able to scale according to peaks and troughs in usage (Manoj A. Thomas, 2009), is modular in the way components are reused and code is arranged as well as more maintainable by a team of developers that are trained in relevant new technologies.

Conceptual Architectural Views, with a focus on the Development View

Mon, 18 May 2020 11:20:54 +0000

What is Conceptual Architectural Views?

Architectural views are abstractions, or simplifications, of the entire design, in which important characteristics are made more visible by leaving details aside. (Eclipse, n.d.)

They are divided into four main sub-categories as illustrated below when using the 4+1 modelling system:

Each of the above segments paints a different perspective view on the architecture of a complex system, allowing for a simplified look into the inner workings and how everything works together.

Assessing Reusable Parts in a Software Architecture

Sun, 17 May 2020 13:00:43 +0000

During the Software Development Life Cycle (SDLC) the development team will come to realise that parts of any application have already been created before and there is the potential for those parts to be reused time and again going forward.

In the last few years, the culture of software development has moved towards Q&A sites such as StackOverflow to answer common daily problems that developers face. This has also led to many “Accepted Answers” being associated with these common issues and many developers have become quite indolent and simply copy/paste the code snippets directly from these types of websites straight into their application code they plan to ship. If and when it then resolves the problem they are facing, there is a high chance that the pasted code will eventually find it’s way into a production environment as is, or with very little change whatsoever.

An Introduction to 2-Tier and 3-Tier Client-Server Systems

Sat, 16 May 2020 12:31:00 +0000

All software systems can be grouped in either a 2-tier or a 3-tier formation.

The former is essentially where all clients contain application and business logic code to read from a datastore themselves (STC, n.d.) and the latter by comparison relies on a thin client that talks to an application layer server that contains business logic which in turn communicates with the datastore.

Remove the Outermost Parentheses using Python

Fri, 15 May 2020 10:13:40 +0000

The Question

A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and + represents string concatenation. For example, "", "()", "(())()", and "(()(()))" are all valid parentheses strings.

A valid parentheses string S is primitive if it is nonempty, and there does not exist a way to split it into S = A+B, with A and B nonempty valid parentheses strings.

The Pros and Cons of Agile in Software Development

Thu, 14 May 2020 11:11:31 +0000

What is Agile in Software Engineering?

Agile approaches help teams respond to unpredictability through incremental, iterative work cadences and empirical feedback. (AgileMethodology.org, 2008)

Advantages of Agile

FlexibilityPotentially the main advantage to Agile is the ability to be more ?flexible? or ?agile? in terms of evolving a project as it develops as opposed to taking on a mammoth list of project requirements and only being able to show the customer the end result at project completion. (Kelly Waters, 2007)
VisibilityBy undertaking a defined list of ?tasks? per ?sprint?, it allows all involved business units and customers to see the project unfolding at regular checkpoints before their eyes and provides the ability to make informed decisions about what additional backlog tasks should be added or removed for an overall better final project goal.
Ability to make iterative changesTaking on smaller pieces of work allows developers to not be stuck with large refactoring of code when big sections of the project need to be re-worked at a later stage. (Alexander Mikula, 2015)
Development led project managementBy giving project management tasks back to the development team, team members are aligned in what needs to be done and they have an knowledgeable invested interest in excelling at their individual tasks laid out by themselves.
Cost controlUndertaking sections of work at a time highlights how much of the project has been completed and what still needs to be done. This allows feature requests and backlog items to be aligned with remaining budgets allocated to the project.

Disadvantages of Agile

Scope creepCustomers/analysts add features/tasks as the project evolves, making it difficult to complete the project without adding additional scope. (Stephen Haunts, 2014)
Does not scale wellTeams should be no more than approximately 10 members otherwise it gets harder to manage (Robert Galen, 2015).
Requires more re-workTasks undertaken separately without knowledge of the wider project roadmap, code often needs to be refactored to make room for additional specifications at a later stage.
Demanding on participants timeWith developers involved in: planning, design, implementation, demos, retrospectives and more; it can be difficult to allocate a decent amount of time towards ?coding? per sprint. Often spending over 20% time on discussions per sprint. (Andrew Odendaal, 2016)
Testing costs can be higherNeed for QA to test each feature each sprint as opposed to only at the end of the project, this can add a lot more cost and resource. (Donald Patti, 2010)

Agile can be negative on a project when you have inexperienced developers that need hand-holding and are not able to take on tasks by themselves, there is a steep learning curve and more senior developers will need to spent a lot more time managing the processes.

Contemporary and beneficial uses of Big-Data Systems

Wed, 13 May 2020 13:28:00 +0000

Big data is a term applied to datasets whose size or type is beyond the ability of traditional relational databases to capture, manage, and process the data with low-latency. (IBM, 2018)

The V’s of Big Data

They share at least one or more of the common V’s; known as Volume, Velocity and Variety.

Distributed Database Systems Observations

Tue, 12 May 2020 12:01:00 +0000

Traditional database systems were a centralised powerful database server that housed all operations pertaining to the database.

There are countless reasons that this is unsustainable when larger databases are employed, specifically for globally distributed companies and popular applications as already known today.

A single database server may suit many database’s requirements, but at some point, there may be a need to scale up to support higher demand or for global capacity requirements of sorts (Shalom, 2017).

Functions of an Operating System

Mon, 11 May 2020 09:58:00 +0000

I am in a bit of an unusual situation where “I use” a combination of three different laptops, which each run different platforms. Namely; MacOS primarily at work with a combination of Linux servers and then Windows as well as Ubuntu on two separate home laptops that I switch between on my desk all the time between tasks.

ORDER BY RAND() – Faster Alternative

Sun, 10 May 2020 16:48:29 +0000

MySQL’s ORDER BY RAND() function can be so useful for returning random items from a table, in fact, we have used it a million times over the years.

The problem comes when your database tables start getting really big.

We found a very nice alternative to using it and thought it useful to post here for everyone else to use and/or provide feedback on.

Say you have a SQL query as follows: (slow on big tables)

Top-down vs Bottom-up Database Design

Sat, 09 May 2020 11:34:00 +0000

There are essentially two different approaches one can take when designing databases; these, from a high-level analytic point of view, narrow down to what is typically called “Top-down” and “Bottom-up” philosophies or methods.

While these methodologies can appear profoundly unique, they share the shared objective of joining a system by portraying the greater part of the association between the procedures.

How to keep your web server or blog up when you get a traffic spike

Fri, 08 May 2020 13:00:00 +0000

So you’re about to be featured on some very high ranking website.

You’re worried that when all the visitors come rushing towards you, your web server?is going to crash and burn.?Well, you’re probably right!

Did you know that 95% of all websites on the internet are not able to handle more than 30 concurrent visitors the way they are setup?

Even worse still, most websites run off of either Shared hosting or un-tweaked VPS configurations that are not meant to handle many visitors in the first place.

How to get the UTC Timestamp in Python

Thu, 07 May 2020 08:36:00 +0000

All dates in your server applications should be stored in the UTC timezone.

This is because you always want to store time without the offset of the timezone you may be working in.

Clients of your application may be in many different timezones around the world. However, storing all data in the UTC or GMT (same thing) timezone, is ideal as it gives your application the ability to present times and dates back in the same methodology.

How to setup the AWS CLI for multiple profiles

Wed, 06 May 2020 09:54:56 +0000

The AWS CLI provides the ability to use the wide range of Amazon Web Services tools and services straight from the command-line. If you’re working with AWS, you might also be interested in how to push Docker images to AWS ECR or how to get the size of an AWS S3 bucket.

However, sometimes it’s useful to be able to login to multiple AWS accounts. Luckily, this is possible by adding an additional profile to your local configuration and then specifying it when making calls to respective services. This is especially useful when making HTTP requests in AWS Lambda using Python.

How to get the size of an AWS S3 bucket

Tue, 05 May 2020 09:03:13 +0000

If you need to get the size of an AWS S3 folder, or even an entire bucket, you can do so with the following command:

If you don’t use aws cli profiles, then you can leave out the profile part like this:

Remember to replace <bucket_name> with your own bucket name.

Comparing Java and Javascript

Mon, 04 May 2020 12:14:51 +0000

Perhaps the first thing that most people ask when they hear the names of these two programming languages are. “Why do they have the same name?” and “Are they the same thing?”.

There is a general misconception that because Java and Javascript share a similar name to one another, that they are indeed one and the same; but in reality, they are very different languages, which each address different types of problems and only share the smallest of traits.

An Introduction to Data Structures

Sun, 03 May 2020 00:53:54 +0000

When bringing up the topic of “Data Structures”, it is first important to understand what they are. TechTarget states that “a data structure is a specialized format for organizing and storing data”. This provides a high-level definition to get you started; so let’s explore it a little deeper.

Below are a few examples of common data structures:

Primitive types: Boolean, Integer, Double, Character, String

Composite/Non-primitive types: Array, Record, Union

Abstract types: List, Associate Array, Stack, Queue, Tree

Relational Database Proprietary Extensions

Sat, 02 May 2020 02:14:00 +0000

Standard Query Language – or SQL for short – is a language designed for relational databases that allows end users such as developers and database administrators (DBAs) to manipulate data.

Whether that be INSERT-ing, UPDATE-ing, DELETE-ing, SELECT-ing or otherwise ALTER-ing almost any amount of data; SQL provides an effective way of utilising the database system/engine by providing standardised language to do so.

Locks used in Database Management Systems

Fri, 01 May 2020 12:24:40 +0000

Database Management Systems (DBMS?) are designed to store any amount of data that can then be retrieved or manipulated at a later date.

In order to make sure that the data can be concurrently utilised in parallel by numerous processes or users, it is important to have some form of Locking enforced so that if a particular record is being modified or created, then another process is not allowed to simultaneously adjust the same record. If databases did not appoint locks, then the data could easily be overwritten and therefore become inconsistent and corrupt.

Tail and Grep: display all output but highlight search matches

Thu, 30 Apr 2020 11:24:17 +0000

I tail logs quite a lot.

An example would be to tail the Apache2 access logs.

This is simple to do:

tail -f /var/log/apache2/access.log

This will show a trail of all access log entries as they come in.

What if we only wanted to see when Googlebot accessed the site?

Highlight entries

We could filter only these results:

tail -f /var/log/apache2/access.log | grep -i googlebot

This will tail all logs, and grep will only shows results for case-insensitive instances of googlebot entries.

Convert URL String into a Javascript Object

Wed, 29 Apr 2020 09:43:31 +0000

Sometimes you find yourself with a String, something like and you want to repeatably access elements of it correctly.

Let’s say that you want to only get the origin of a URL, or maybe the host, or even protocol, how would you do this?

The URL object

Javascript brings you the URL object, which allows you to instantiate it with a string, and optionally a base to work from.

How to make an HTTP Request in AWS Lambda using Python

Tue, 28 Apr 2020 09:28:05 +0000

The requests module for Python is very useful in helping simplify HTTP/s requests from Python, but how would you use it in an AWS Lambda script?

Option 1 – Use `requests` import

The requests library is very popular among Python enthusiasts.

You will need to create a custom lambda layer and include requests

This will allow you to use import requests in your code.

Download the folder package

pip install requests -t .

Run this command on your local machine, then zip your working directory and upload to AWS.

How to fix a Javascript Uncaught ReferenceError

Mon, 27 Apr 2020 10:13:14 +0000

Sometimes you may get an error that looks something like this:

Uncaught ReferenceError: <some_variable_or_function> is not defined

At first this can be quite the pain, but it usually just means that that variable, or function has either not been defined, or it isn’t ready for use yet.

It’s good practice to wrap this bit of code into a conditional check.

The original code

if (variable_or_function) {
    //console.log(variable_or_function);
}

The improved code

if (typeof variable_or_function !== 'undefined') {
    //console.log(variable_or_function);
}

Alternate methods

Does not execute if yourvar is undefined:

Resolving InsufficientPrivilege Errors in Redshift

Sun, 26 Apr 2020 15:36:39 +0000

If you are getting the mysterious error:

[ERROR] InsufficientPrivilege: permission denied for schema errors

Then you can easily resolve this by running the following SQL:

GRANT USAGE ON SCHEMA <schema_name> TO <redshift_user>;

Another common error that often follows this, is:

[ERROR] InsufficientPrivilege: permission denied for relation <table>

Luckily, this too can be resolved by running the following SQL:

GRANT USAGE ON SCHEMA <schema_name> TO <redshift_user>;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA <schema_name> TO <redshift_user>;

How to increase column size in Redshift database tables

Sat, 25 Apr 2020 03:47:46 +0000

It is only possible to alter VARCHAR columns, and only under the following circumstances:

You can not alter a column with compression encodings BYTEDICT, RUNLENGTH, TEXT255, or TEXT32K.
You can not decrease the size less than the maximum size of existing data.
You can not alter columns with default values.
You can not alter columns with UNIQUE, PRIMARY KEY, or FOREIGN KEY.
You can not alter columns inside a multi-statement block (BEGIN...END).

SQL to increase the size of (Redshift Alter Table)

It’s very simple to perform a Redshift Alter Table command to alter the column length, or alter the column varchar length:

[Solved] The provided execution role does not have permissions to call CreateNetworkInterface on EC2

Fri, 24 Apr 2020 10:36:30 +0000

If you are trying to get an AWS Lambda added attached to a VPC, but get the error message:

The provided execution role does not have permissions to call CreateNetworkInterface on EC2

There are 3 ways to solve this problem

Below we will look at 3 different options when it comes to solving this problem:

Fix the problem in Terraform
Fix the problem in CloudFormation / SAM
Fix the problem Manually in the AWS Console

How to fix the problem in Terraform

resource "aws_iam_role_policy_attachment" "AWSLambdaVPCAccessExecutionRole" {
  role       = aws_iam_role.lambda.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaVPCAccessExecutionRole"
}

How to fix the problem in CloudFormation

Type: "AWS::IAM::Role"
Properties:
  RoleName: "lambda-with-vpc-access"
  ManagedPolicyArns:
    - "arn:aws:iam::aws:policy/service-role/AWSLambdaVPCAccessExecutionRole"
  AssumeRolePolicyDocument:
    Version: "2012-10-17"
    Statement:
      - Effect: Allow
        Action:
          - sts:AssumeRole
        Principal:
          Service:
            - lambda.amazonaws.com

How to fix this problem Manually in the AWS Console

Then you can resolve this by adding a custom Inline Policy to the Lambda execution role under the Permissions tab.

Entity and Referential Integrity in Relational Databases

Thu, 23 Apr 2020 15:27:00 +0000

Data integrity is the overall completeness, accuracy and consistency of data (Techopedia, n.d.).

In order to achieve data integrity, it is important to analyse Entity and Referential integrity constraints.

Entity Integrity

Focuses on Primary keys.

Each table should have a primary key and each record must be unique and not null.

Data Warehouses vs Data Marts

Wed, 22 Apr 2020 12:13:00 +0000

Although the terms “data warehouse” and “data mart” sound similar, they are quite different. It is important to first understand how they differ in order to define some characteristics and practical applications for each.

Serra (2012) has a great explanation of data warehouses as being “a single organizational repository of enterprise-wide data across many or all subject areas”; while Inmon classifies the data mart as “a logical view or a physical extract of a larger data warehouse, usually isolated for the need to have a special data model or schema” (n.d.).

Amazon’s custom Whois date entry

Tue, 21 Apr 2020 08:39:40 +0000

Whois is an online service that let’s you know registration information about a website or IP address.

For the most part, Whois aggregations are not that standard, however, per gTLD (.com, .net, .yourkitchsink) they try their best to apply the same overall guidance and regulatory patterns.

Most individuals, as well as businesses will go about registering their domain name through a service such as GoDaddy, Namecheap, or some other common domain registrar.

Graph Databases and their Properties

Mon, 20 Apr 2020 11:41:45 +0000

The concept of a graph in mathematics is simply a collection of elements which are typically called Nodes and are joined together by Edges. Each Node represents a piece of information in the graph and each Edge represents some relationship or connection between any of the two Nodes (Cox, 2017).

A graph database is simply a database that models itself on the connections that Nodes represent in a mathematical graph structure.

How to add SSH keys to GitHub

Sun, 19 Apr 2020 02:08:54 +0000

When working with GitHub, you will need to identify yourself. The default way is using your username and password. However, you can also create an SSH key-pair that can be used instead.

By using this technique, you can generate a password and not have to use it each and every time.

You can also reuse your machine’s generated key-pair for other SSH services.

A private and public key is created locally on your machine, and the private key always stays on your own machine. The public key can then be shared with services such as GitHub.

Get the Maximum Length of a Concatenated String with Unique Characters in Python

Sat, 18 Apr 2020 12:00:04 +0000

The problem

Given an array of strings arr. String s is a concatenation of a sub-sequence of arr which have unique characters.

Return the maximum possible length of s.

Example test-cases

Example 1:

Example 2:

Example 3:

Constraints

1 <= arr.length <= 16
1 <= arr[i].length <= 26
arr[i] contains only lower case English letters.

How to write the code

def maxLength(arr: List[str]) -> int:
  result = [float('-inf')]

  unique_char("", arr, 0, result)

  if not result[0] == float('-inf'):
    return result[0]
  return 0


def unique_char(cur, arr, index, result):
  # End of the array
  if index == len(arr):
    return

  # Iterating from the current word to the end of the array
  for index in range(index,len(arr)):

    # If current word + next word have all unique characters
    if len(set(cur + arr[index])) == len(list(cur + arr[index])):
      # Compare the actual lenth with the previous max
      result[0] = max(result[0],len(cur + arr[index]))
      # Make a new call with concatenate words
      unique_char(cur + arr[index], arr, index + 1,result)

Apache Kafka’s Role in Big Data Streaming Analytics

Fri, 17 Apr 2020 12:15:55 +0000

The world of Big Data started out as a way of storing and querying obscene amounts of information by comparison to what yesteryears were able to achieve. However, most value in said data is primarily found in the real time or streaming information that is presented as it first enters the system. As data gets old, it also gets stale and less useful to many business systems.

Streaming analytics platforms have come a long way with numerous open source projects offering advanced products such as Flink, Spark Streaming, Samza and Storm; which are all at the forefront of the arena in their respective strengths.

Mitigating Risks with Software Development Outsourcing

Thu, 16 Apr 2020 12:30:46 +0000

In the Oxford Dictionary, the term “outsourcing” is simply defined as obtaining goods or services by contract from an outside supplier (OxfordDictionaries.com, n.d.).

When it comes to software development, the same is true, with many companies opting to use economically cheaper labour to extend or swap out their workforce in order to enhance their endeavours and reduce costs across the board.

Countries such as India, Russia, China and Mexico have a lower Cost of Living (Numbeo.com, 2017) and are among the most common places to outsource to (Lisa DiCarlo, 2003).

The Primary Data Types in Java

Wed, 15 Apr 2020 11:08:00 +0000

In Java there are eight basic data types; which are: byte, short, int, long, float, double, boolean and char.

It could realistically be said that a Java developer’s time is primarily spent using these particular variable types to store, retrieve and manipulate data to complete most programming tasks. However, there are many times that these primitive variables don’t quite suffice and additional data types need to be explored and used instead.

Comparing Objects in Java

Tue, 14 Apr 2020 08:16:00 +0000

TLDR;

When to use `==` in Java

When comparing two operands. It is used to check whether two operands are equal or not.It’s best to only use it when working with primitive data types, such as int, float, char or sometimes even Booleans

Overloading Operators in Java

Mon, 13 Apr 2020 03:42:00 +0000

As with many programming languages such as C, C++ and C# (known commonly as the C family), it is possible to “overload methods” (sometimes called functions if not used in classes, such as C) in order to take a different amount of parameters so that they can be used in multiple scenarios with similar internals.

As Java is derived from the C style of languages (C family), it too can perform Method Overloading.

uncaught typeerror: $ is not a function

Sun, 12 Apr 2020 10:45:08 +0000

The dollar-sign ($) in Javascript has for many years now been associated with jQuery.

When you see this error:

“uncaught typeerror: $ is not a function”

It almost always means that a jQuery piece of code is being run before the jQuery library has been initialised and loaded.

Oftentimes, your code will wait for jQuery to load before continuing any processing, this is almost always done as follows:

$(document).ready(function(){
    // jQuery code is in here
});

However, it’s not uncommon to get an “TypeError: $ is not a function” error in response.

How to get the last element of a list in Python

Sat, 11 Apr 2020 13:55:02 +0000

Let’s say that you have a Python list with the following 5 foods:

foods = ["pizza", "pasta", "steak", "chicken", "olives"]

How do we go about getting the last item?

Option 1

It’s actually really easy, you can select the index item by it’s total length minus one.

last_item = foods[len(foods)-1]

# "olives"

Option 2

Python has some really fantastic functionality around making your life easier. One of those such things is the ability to use slices.

How to embed a web server in your Python3 app

Fri, 10 Apr 2020 09:50:13 +0000

This is not the first time that I created a Python3 application that spat out some output and required access to it via an HTTP server.

While there are numerous ways to achieve this, a really simple way is to embed an HTTP server directly in your Python3 application, and have it serve your output directly when called.

A sample web server in Python

from http.server import HTTPServer, BaseHTTPRequestHandler


class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):

    def do_GET(self):
        self.send_response(200)
        self.end_headers()
        # Add additional output here
        self.wfile.write(b'Hello, world!')


httpd = HTTPServer(('', 8000), SimpleHTTPRequestHandler)
httpd.serve_forever()

How to get the Range Sum of Binary Search Tree using Java

Thu, 09 Apr 2020 09:48:26 +0000

Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive).

The binary search tree is guaranteed to have unique values.

Examples

Example1:

Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
Output: 32

Example2:

Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
Output: 23

Our solution in Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int rangeSumBST(TreeNode root, int L, int R) {
        //output variable
        int output = 0;
        
        // Create a stack
        Stack<TreeNode> stack = new Stack();
        // Add the root node
        stack.push(root);
        
        // loop through each element 
        while (!stack.isEmpty()) {
            
            // remove last item from stack
            TreeNode node = stack.pop();
            // if the node exists
            if (node != null) {
                
                // incrememnt output counts
                if (L <= node.val && node.val <= R)
                    output += node.val;
                
                // push if left
                if (L < node.val)
                    stack.push(node.left);
                
                // push if right
                if (node.val < R)
                    stack.push(node.right);
            }
        }
        
        // return our count
        return output;
    }
}

How to duplicate zeros in place using Python

Wed, 08 Apr 2020 14:00:15 +0000

Given a fixed length array arr of integers, duplicate each occurrence of zero, shifting the remaining elements to the right.

Note that elements beyond the length of the original array are not written.

Do the above modifications to the input array in place, do not return anything from your function.

Examples

Example1:

Input: [1,0,2,3,0,4,5,0]
Output: null
Explanation: After calling your function, the input array is modified to: [1,0,0,2,3,0,0,4]

Example2:

Input: [1,2,3]
Output: null
Explanation: After calling your function, the input array is modified to: [1,2,3]

Writing the code

# declare our function
def duplicateZeros(arr):

    # create our incrementor
    i = 0

    # loop through all dynamic elements
    while i < len(arr)-1:
        # if the character is a zero
        if arr[i]==0:
            # remove the last item from the array
            arr.pop()
            # insert a zero in front of current element
            arr.insert(i+1, 0)
            # move one place forward
            i += 1

        # increment to the next character
        i += 1

A Quick Introduction to Asyncio in Python3

Tue, 07 Apr 2020 12:26:10 +0000

Python has never been the best at doing multiple things at the same time.

While there are ways to mostly resolve this, such as using the Multiprocessing library, it always seems a bit make-shift to me.

So many other languages have fantastic ways of resolving these types of issues, and Python now has an Async way too!

Introducing Asyncio

https://docs.python.org/3/library/asyncio.html

How to replace newlines with commas in CLI

Mon, 06 Apr 2020 11:10:00 +0000

If you need to replace all newline characters with a comma, or perhaps some other delimiter, then using the build-in tr utility will work very well for you.

Possible use-cases for this is if you need to transport a configuration file with multiple lines into a single input field, or store the file’s contents within an environment variable.

My personal use-case was to store an ~/.aws/credentials file in an environment variable.

How to make a disk cache using PHP

Sun, 05 Apr 2020 17:04:01 +0000

If you have a busy PHP driven website and don’t want to make constant queries to the database for each user that will see the same data, then you can easily resolve this problem by letting the first of these visitors generate a cache for the consecutive visitors. This technique is similar to other PHP performance optimizations like using a PHP mail class or sending data from JavaScript to PHP.

Letting this cache last for a few minutes allows your database to not get overloaded and allows for a much faster website experience as well as a much cheaper hosting bill for you at the end of the month.

How to remove files without a certain extension?

Sat, 04 Apr 2020 09:34:11 +0000

You have a directory with a lot of files, and you want to delete only the files that don’t match a specific extension.

This is a simple task when using the find command-line utility.

Delete a single extension

You can delete all files that do not have the following *.txt extension:

find . -type f ! -name "*.txt" -exec rm {} \;

Delete multiple extensions

You can delete all files that do not have the following *.txt or *.exe extensions.

How to debug an Apache 404 error

Fri, 03 Apr 2020 14:55:11 +0000

So you are getting an error 404 or perhaps even worse, a 500!

The error in your Apache2 logs looks something like this:

***.162.245.*** - - [03/Apr/2020:12:49:50 +0000] "GET /robots.txt HTTP/1.1" 404 89670 "-" "Mozilla/5.0 (compatible; SomeUserAgent/2.1; +https://example.com)"

In a perfect world, you’d only have a single site/domain on this host, so will know that the robots.txt file would reside in the Apache root serving directory.

However, I just happen to (as you?) have a ton of VirtualHosts on this machine, so am not sure which robots.txt file is missing..

How to Reorder Data in Log Files using Python

Thu, 02 Apr 2020 12:08:06 +0000

Let’s say that you have an array or a list, or logs.

Each of these logs is a space-delimited string of words.

For example:

logs = ["dig1 8 1 5 1","let1 art can","dig2 3 6","let2 own kit dig","let3 art zero"]

The task is to reorder these logs and return them in the following acceptance criteria:

The first entry (identifier) of each log is ignored but still returned
The letter-logs are returned before the digit-logs
The identifier is only used to sort these there is a tie

How to analyse the problem

At first glance, this appears to be something that could be easily solved by looping through each log entry and if the second part of the entry is a string type, then adding it to a tempA list, otherwise adding it to a tempB list.

Another WTF Javascript Moment

Wed, 01 Apr 2020 14:06:51 +0000

Javascript is a powerful language, but sometimes it doesn’t always do what you expect it to.

Take the following expression for example. It’s a simple if statement that checks to see if true and then runs the code within the block.

Running the code results in the block being executed, however, when we directly compare the statement’s comparison against a false value, we can see that it is in fact, not actually true.

How to Bring Back GROUP BY in MySQL

Tue, 31 Mar 2020 10:28:13 +0000

If you are suddenly not able to perform GROUP BY statements as you used to after a MySQL/MariaDB version update, then you will have noticed the change forced upon you.

You can re-enable the previous GROUP BY behaviour by editing your /etc/mysql/my.cnf and adding in the following line below the [mysqld] section:

[mysqld]
sql_mode = "STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

This will allow you to GROUP BY without having to return all those specific columns as well.

How to implement a Queue using Stacks in Python

Mon, 30 Mar 2020 11:01:58 +0000

A common programming interview question, and for a change, one that you will actually be able to use in the job, is that of implementing a Queue by means of using Stacks in Python.

The 5 common operations of a Queue

Instantiation
push(val)
pop()
peek()
empty()

What each operation does

Instantiation is the Queue’s storage object that will be used.

class MyQueue:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.stack = []

push(val) is the way to add data to the Queue.

Find positions of largest groups of characters in a String with Python

Sun, 29 Mar 2020 14:53:15 +0000

The question

Take a string S of lowercase letters.

These letters form consecutive groupings of like characters.

Find groups with 3 or more like characters and return a list of lists of starting and ending index for each character group.

Elaboration and examples

If we show an example, we could say S = "abbcccdeffffy".

This string has 2 groups, c and f who’s consecutive characters are of 3 or more.

How to make Git “forget” about a file that was tracked but is now in .gitignore?

Sat, 28 Mar 2020 12:17:13 +0000

You can ignore certain files and folders from being committed to Git by means of including a .gitignore file.

Unfortunately, you may have forgotten to include certain entries and now find that there are files and/or folders that git will want to commit.

To start with, you should make sure that the relative path to the file or folder is included in your .gitignore file.

Then run one of the below commands.

How to Purge the BinLog for MySQL and MariaDB

Fri, 27 Mar 2020 12:30:51 +0000

If you see lots of disk space quickly disappearing on your MySQL or MariaDB server, then you may want to look into the BinLog directory, it is located at /var/log/mysql/.

In my case I saw this:

usr@server-1:/var/log/mysql# ll
total 5571044
drwxr-s---  2 x x         4096 Mar 25 18:18 ./
drwxrwxr-x 12 x  x      4096 Mar 25 05:25 ../
-rw-rw----  1 x x    104857748 Mar 23 09:29 mariadb-bin.000301
-rw-rw----  1 x x    104859422 Mar 23 10:07 mariadb-bin.000302
-rw-rw----  1 x x    104857708 Mar 23 11:10 mariadb-bin.000303
-rw-rw----  1 x x    104860750 Mar 23 12:29 mariadb-bin.000304
...truncated...
-rw-rw----  1 x x    104857809 Mar 25 16:46 mariadb-bin.000352
-rw-rw----  1 x x    104858231 Mar 25 17:17 mariadb-bin.000353
-rw-rw----  1 x x    104857709 Mar 25 18:18 mariadb-bin.000354
-rw-rw----  1 x x     24833125 Mar 25 18:32 mariadb-bin.000355
-rw-rw----  1 x x         1870 Mar 25 18:18 mariadb-bin.index

I looked to see how much space this was all taking:

How to Measure Execution Time in Google Colab

Thu, 26 Mar 2020 16:19:21 +0000

Google Colab is a fantastic environment to write Python code using Jupyter Notebooks, hosted for free by Google.

If you’ve ever used Jupyter Notebooks before, it is the same principle, you write Python code in a cell and you are able to execute each cell as you require.

Measure Execution Time

But how would you measure the time each cell takes to execute?

How to fake a User Agent in Python

Wed, 25 Mar 2020 14:49:49 +0000

A User-Agent is a bunch of text that is sent with every HTTP and HTTPS request. The server processing this request is able to determine what type of device and browser has made the request.

Often times servers use this parameter to restrict access to the resource.

However, it’s easy to fake a User-Agent when using Python to make HTTP and HTTPS requests.

Using Requests Library

import requests

user_agent = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.149 Safari/537.36'

response = requests.get('https://andrewodendaal.com', headers={'User-Agent': user_agent})
html = response.content
print(response.content)

Using URLLib Library

import urllib.request

user_agent = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.149 Safari/537.36'

request = urllib.request.Request('https://andrewodendaal.com', headers={'User-Agent': user_agent})
response = urllib.request.urlopen(request)
html = response.read()

How to Delete from a Table where rows match in Another Table – MySQL

Tue, 24 Mar 2020 09:58:34 +0000

So you have a table where you want to delete a bunch of rows, based on a particular column being matched in another table.

This is easily achievable with MySQL.

DELETE FROM TABLE1
WHERE domain IN (
	SELECT domain FROM TABLE2
)

The above SQL will delete all rows in TABLE1 that are found in TABLE2.

But what if we need to limit which records are returned from TABLE2?

That’s simple too. All we need to do is add a traditional WHERE clause to our select statement.

REPLACE INTO instead of INSERT INTO – MySQL

Mon, 23 Mar 2020 13:52:24 +0000

There are many occasions where you need to INSERT a record into a MySQL database table, but the record already exists.

INSERT INTO queue_domains (domain) VALUES('statvoo.com')

This will result in a Duplicate entry 'statvoo.com' for key 'domain' error

A nice and simple way to resolve this is to use REPLACE INTO instead.

This will look to see if the item already exists and will simply replace it.

This is faster than doing a SELECT followed by an INSERT.

Read the bottom n lines of a file in Python

Sun, 22 Mar 2020 11:02:44 +0000

Using Operating System Commands in Python

Use the Linux/Mac tail command to provide the data:

line = subprocess.check_output(['tail', '-1', somefile.txt])

Creating a Python Only Script

Read the whole file into memory and only print out the last line/s:

with open('somefile.txt', 'r') as f:
    lines = f.read().splitlines()
    last_line = lines[-1]
    print(last_line)

How to Format a Number as a Currency in Javascript

Sat, 21 Mar 2020 13:54:03 +0000

There are quite a few ways to format a number as a currency value in Javascript. This is a common task when building web applications, similar to other string manipulations like removing hash from window location or checking if a string contains a substring.

Doing it yourself

The easiest of which is that of using the built-in toFixed() method.

Often times you will either have a string, integer or floating-point number (/double) and will need to output a value that looks like a currency.

How to Change the Timezone on Ubuntu Server

Fri, 20 Mar 2020 10:42:32 +0000

If you’ve ever typed date into your Ubuntu Server and seen a different time or timezone appear than you expected, then it probably means that this tutorial is for you.

Check current timezone

Start by checking what data is returned using the following command:

timedatectl

In my case, I wanted to make sure my server’s time was in UTC, London. However, it was reported as being in Berlin.

$ timedatectl

                      Local time: Fri 2020-03-20 11:08:41 CET
                  Universal time: Fri 2020-03-20 10:08:41 UTC
                        RTC time: Fri 2020-03-20 10:08:42
                       Time zone: Europe/Berlin (CET, +0100)
       System clock synchronized: yes
systemd-timesyncd.service active: yes
                 RTC in local TZ: no

Ubuntu uses symbolic files to link configurations for timezones.

How to make a Python script Pip-installable

Thu, 19 Mar 2020 10:28:25 +0000

As Python developers, we’ve all used pip to install applications, but speaking to other Python developers, it’s not always clear how to make your own application/script pip-installable.

automation tip

Steps involved

Create a python script, or application
Add and configure a setup file
Build your new Pip Package Locally
Upload them both to the Python Package Index (PyPi)

So let’s run through these 4 steps to get you going.

How to Host an AngularJS site on AWS S3

Wed, 18 Mar 2020 11:24:10 +0000

AngularJS is a Javascript Framework that allows you to create dynamic front-end web applications easily.

I have traditionally packaged these applications through NodeJS, and Grunt (or Gulp) in particular.

Once it needs to be hosted for the whole world to see, I always used to push the static folder up to an Apache2 or Nginx Linux web server.

There’s really not a massive need for this though, as it’s easily possible to AngularJS applications completely serverless using a combination of AWS S3 and Cloudflare.

How to send emails using Python and AWS SES SMTP

Tue, 17 Mar 2020 10:52:40 +0000

Sending emails using Python and AWS’ SES service is really easy. They provide an SMTP server that you can authenticate against and send email programmatically from your python scripts.

There is a wonderfully simple Python package called emails I like to use for this purpose.

If you’re not running a Python Virtual Environment, then start by getting started here.

Otherwise, continue reading!

Getting AWS SES SMTP Setup

In order to start sending emails using AWS SES, and the SMTP server in particular, you will need to:

Generate a random number between two numbers in JavaScript

Mon, 16 Mar 2020 16:30:08 +0000

If you need to generate a random number between two numbers in JavaScript, then you are in the right place! Here you will learn javascript random number generation.

We can easily do this by using a combination of built-in Math functions.

Javascript Random Number from Math.random()

Let’s start by using Math.random() to generate a random number. Now we will take that and multiply it by max - min + 1.

Why Password Managers are Not the Solution

Sun, 15 Mar 2020 16:51:35 +0000

Why a Password Manager?

Password managers exist for two main reasons.

Firstly, to generate strong passwords and secondly so that you don’t end up using the same password on all your websites or apps that you frequent.

On the surface, that sounds like a pretty good idea.

Imagine you use the same password for a number of websites, then one of those websites gets hacked. The hackers will now try the same credentials on a range of sites. Oftentimes they will be able to successfully login because people don’t protect their stuff more than this.

Read the top n lines of a file in Python

Sat, 14 Mar 2020 10:56:00 +0000

Sometimes you may need to read the top n lines of a file using Python.

We start by opening the file for reading and then using a list comprehension we iterate through the range of lines we want to return:

N = 10
filename = "file.txt"

with open(filename) as myfile:
    head = [next(myfile) for x in range(N)]

print(head)

Another way you can do this is by looping through each line individually:

How Fast is your Website?

Fri, 13 Mar 2020 12:52:37 +0000

I operate a bunch of different sites and have done for many years now.

Some of them get quite a lot of traffic and require a high level of uptime.

To monitor the uptime of these sites, I use various tools to alert me when a site is unreachable, when a specific resource is returning an unexpected status code, or if one of the database heavy pages starts taking a while to respond to requests.

How to Git Reset a Single File

Thu, 12 Mar 2020 09:28:56 +0000

It’s very easy to reset files that have not yet been committed to git.

Reset a single file

git reset <filename>

You can also specify the filename as the path to the file, like so:

git reset ./the/actual/relatvive/path/with/filename.ext

This will checkout the file from HEAD.

It is important to note that should you have a file that is the same name as a branch, you will need to rather run the following command:

Introducing Variables in Golang

Wed, 11 Mar 2020 14:07:14 +0000

Golang comes with a decent offering around variables that you can use to store, retrieve and manipulate information.

A variable is defined with the var keyword followed by the name of the variable, the type and then the assignment itself.

How to name a variable in Golang

Variable names must:

Start with a letter
May contain letters, numbers or the underscore _ character.

Variable names that start with numbers or special characters are not allowed.

Golang cannot convert (type string) to type int

Tue, 10 Mar 2020 08:00:00 +0000

Every language has it’s ways of converting data types. One of the most common data types to convert between is that of strings (string) and integers (int).

If you’ve ever tried to do this in Golang, you would know that’s it isn’t all that simple at first.

The easiest way to convert between String and Integers in Golang is as follows:

String to Integer

My go-to option to resolve this problem would be with the strconv module.

Learn Golang as a Python Developer

Mon, 09 Mar 2020 08:51:37 +0000

Learning Go or Golang as a Python developer, programmer or software engineer is easier than you think.

While there are quite a lot of things to learn and get familiar with, there are many benefits and many common characteristics.

Why learn Go as a Python developer

I find Python to be a very powerful and useful programming language, having used it on a wide range of projects for an even wider range of tasks. From Platform Engineering automation to Machine Learning and Artificial Intelligence, to building User Interfaces and creating APIs as well as building entire websites and web applications. Python has served me well and will continue to do so.

Remove Special Characters in a String using Bash

Sun, 08 Mar 2020 12:39:46 +0000

Programming languages provide the ability to remove special characters from a string quite easily.

Sometimes you need to also do this from your command-line using Bash.

Let’s say we have a bash variable called USER_EMAIL and we want to remove any periods, underscores, dashes and the @ symbol, how would we go about this?

We could pipe our variable to a useful command called tr (which is the translate or delete characters tool) and strip these specifics before pushing the output back to a new bash variable.

Get the Amount of Days Between Two Dates in Python

Sat, 07 Mar 2020 08:22:05 +0000

Let’s say that you have two dates:

"2019-01-29"
"2019-06-30"

How would you create a function that would return the number of days between these two dates?

Introducing the Datetime Package

Python comes with a built-in library called datetime.

We start by importing the date module.

from datetime import date

With this date module, we have access to an object format of the date type.

Writing our Function

Next, we should write our function that takes in two dates and returns the number of days between them.

How to Always run Python 3 from Bash

Fri, 06 Mar 2020 08:29:41 +0000

Given a directory that contains:

|
|- app.py
|- requirements.txt
|- ...
|- <- other-files ->
|- ...

We can create a runme.sh file to always make sure we are running python 3.

Create a shell script

Create a file called runme.sh and put the following code in:

python -c 'import sys; exit(1) if sys.version_info.major < 3 else exit(0)'

if [[ $? == 0 ]]; then
    [ ! -d "venv" ] && virtualenv -p python venv
    . venv/bin/activate
    pip install -r requirements.txt
else
    [ ! -d "venv" ] && virtualenv -p python3 venv
    . venv/bin/activate
    pip3 install -r requirements.txt
fi

python app.py

Now instead of running python app.py or python3 app.py, you can simply run sh runme.sh.

How to Run the Kubernetes Dashboard Locally

Thu, 05 Mar 2020 10:42:42 +0000

Kubernetes comes with a pretty nice dashboard to view clusters, worker groups, nodes and pods. As well as a ton of other useful things.

This tutorial presumes that you already have a Kubernetes cluster setup and running and have access to it through kubectl in your command-line.

Steps to run Kubernetes Dashboard

Start by downloading the metrics-server and applying it to your kubectl config.

DOWNLOAD_URL=$(curl -Ls "https://api.github.com/repos/kubernetes-sigs/metrics-server/releases/latest" | jq -r .tarball_url)
DOWNLOAD_VERSION=$(grep -o '[^/v]*$' <<< $DOWNLOAD_URL)
curl -Ls $DOWNLOAD_URL -o metrics-server-$DOWNLOAD_VERSION.tar.gz
mkdir metrics-server-$DOWNLOAD_VERSION
tar -xzf metrics-server-$DOWNLOAD_VERSION.tar.gz --directory metrics-server-$DOWNLOAD_VERSION --strip-components 1
kubectl apply -f metrics-server-$DOWNLOAD_VERSION/deploy/1.8+/

Next, we will start setting up the metrics-server, ready for action!

How to tell if a year is a Leap Year in Python

Wed, 04 Mar 2020 09:57:02 +0000

Given that we are in a leap year this year (2020), it would be nice to know how to programmatically calculate this.

Luckily, this is a repeatable pattern that we can write some code for.

So what is a leap year?

A leap year is a year that has 29 days in the month of February.

Astronomical years have a quarter of a day more than our calendar years that we follow, so to make sure this matches up continually, our calendar introduces an additional day every 4 years.

How to Reverse a Linked List in Python

Tue, 03 Mar 2020 10:00:25 +0000

It’s important to know about data types and one that comes up fairly regularly is that of Linked Lists.

Let’s write the following base code to create a Linked List.

# Defintion of a single Node
class Node:
  # takes input data and next node
  def __init__(self, data = None, next=None): 
    self.data = data
    self.next = next

# Definition of a Linked List
class LinkedList:
  def __init__(self):  
    self.head = None
  
  # Insert a node into our Linked List
  def insert(self, data):
    newNode = Node(data)
    if(self.head):
      current = self.head
      while(current.next):
        current = current.next
      current.next = newNode
    else:
      self.head = newNode
  
  # Print our Linked List so we can see how it looks
  def render(self):
    current = self.head
    while(current):
      print(current.data)
      current = current.next

Now that we have a base class, let’s insert a couple of nodes and print it out to see what we are working with:

The Docker Quickstart Guide for Developers

Mon, 02 Mar 2020 08:14:00 +0000

This Docker Quickstart Guide for Developers aims to get developers familiar with Docker as quickly as possible.

Providing you with the knowledge to be able to use Docker in your personal and professional projects.

What is Docker?

Docker is a tool written in Golang that provides the ability to run applications within things called containers.

It removes the age-old “works on my machine” problems that plagued many software developers and testers lives.

How to Follow Redirects with cURL for CLI or PHP

Sun, 01 Mar 2020 12:07:17 +0000

Let’s take a really common example. Say we want to follow redirects with cURL for google.com. It is common to curl follow redirect a URL.

Follow Redirects with cURL in the CommandLine

If you navigate directly to google in the command-line using curl, you will be taken to a 301 redirect URL.

curl google.com

#<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
#<TITLE>301 Moved</TITLE></HEAD><BODY>
#<H1>301 Moved</H1>
#The document has moved
#<A HREF="http://www.google.com/">here</A>.
#</BODY></HTML>

This makes sure that you follow the proper canonical URL as set by the particular website in question.

How to tell if a String contains a Substring in Javascript

Sat, 29 Feb 2020 00:27:00 +0000

Javascript comes with some pretty good support for determining if a string contains a substring.

There is the newer includes function which was introduced in ES2015 which allows you to tell if a string contains a substring. This function returns a boolean value of true or false.

'our example string'.includes('example')

// returns true

Alternatively, if you need to either:

Have support for older versions of Javascript
Need to not only know if a string contains a substring, but also it’s position within the string..

Then indexOf is a better match for you.

How to package a Python app (pip) for PyPi

Fri, 28 Feb 2020 01:01:00 +0000

In this tutorial, we will create a Python application that can be installed directly from pip that will show the 10 latest blog posts from this website (the one you are reading this on!).

Getting started

Make sure you have registered at Pypy and have an account, we will need this to upload our package once we’re done.

How to find the longest Palindrome in a String using Python

Thu, 27 Feb 2020 11:24:20 +0000

This occasionally comes up during coding interviews and is actually quite a decent way to test someone’s aptitude of moving back and forth on a string to determine if and where palindromes exist.

If we simply said: “return a boolean if a string is a palindrome”, then threw a couple tests cases at the function, we would expect the developer to loop through the first half of a string while comparing the second half, if it matched all the way to the central pivot, then “yes, the string is a palindrome”.

How to write Anonymous Functions in Javascript

Wed, 26 Feb 2020 08:31:53 +0000

There is a lot of power in Javascript syntax. One of those powerful things is that of Javascript Anonymous Functions.

But what is an Anonymous Function in Javascript?

It is a function that does not have a name or one that has been hidden out of scope around its creation.

A common use of a Javascript Anonymous Function is to guarantee that the same variable names or function names are not already used within the same document.

How to use Docker to test any Linux distribution locally

Tue, 25 Feb 2020 08:19:32 +0000

I often need to test a specific Linux binary or make sure something works as expected from yum install or apt install.

To do this, it’s common to have a virtual machine lying around, or even a VPS that you can just quickly log into.

Things are a bit easier and quicker if you use Docker.

Let’s run two tests, the first one to get going with Ubuntu, and the second to get going with Centos.

How to get the Maximum Depth of a Binary Tree in Python

Mon, 24 Feb 2020 08:15:35 +0000

Let’s say that you have a binary tree and we needed to know it’s maximum depth.

Binary tree input data [3,9,20,null,null,15,7] could be visualised as follows:

In the above example, the depth would be 3. As there are 3 levels.

How would we write some Python code to work this out?

As usual, a TreeNode is defined as follows:

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

As we need to loop through the same data types, this would be a perfect time to practice some recursion!

What is Fizz Buzz?

Sun, 23 Feb 2020 01:32:55 +0000

Fizz buzz is a common programming interview question.

The problem statement usually reads something like this:

Hackerrank.com

If we break this down, the challenge is for us to prove that we know how to:

Loop through a specific set of numbers
Tell if something is a multiple of 3
Tell if something is a multiple of 5
Tell if something is a multiple of both 3 and 5
Know the correct order to check the above cases
Ignore everything else

The main thing here is to know about the modulo operator (%). As that tells us if there are remainders after the division of one number by another.

How to Deploy a Helm “Hello World” app onto Kubernetes

Sat, 22 Feb 2020 00:10:00 +0000

We will create a simple Hello World static HTTP Service using Helm, package it and release it to an AWS EKS Cluster.

This tutorial expects you to have kubectl as well as helm installed on your computer.

Build our Docker image

Create a file called Dockerfile and place the below into it:

FROM busybox
ADD index.html /www/index.html
EXPOSE 8008
CMD httpd -p 8008 -h /www; tail -f /dev/null

Now we need to create our index.html file.

How to write a Quicksort Algorithm in Python

Fri, 21 Feb 2020 10:15:53 +0000

While there are libraries available for all programming languages that offer abilities to sort list, arrays and collections, it is important to know how this is achieved.

Learning how to write a quicksort algorithm yourself gives the ability to better understand the programming language of your choice and how to optimise code where possible.

Today we will explore writing a quicksort algorithm in the Python programming language.

Let’s start by defining a list of integers that are clearly not in order:

How to Reverse a String or List using Python

Thu, 20 Feb 2020 11:15:22 +0000

Python comes with the power of slicing.

Let’s try it with a String:

>>> example1 = 'hello world'

>>> example1[::-1]

'dlrow olleh'

Now let’s try the same with a List:

>>> example2 = ['h','e','l','l','o',' ','w','o','r','l','d']

>>> example2[::-1]

['d', 'l', 'r', 'o', 'w', ' ', 'o', 'l', 'l', 'e', 'h']

As we can see by passing in the third argument to our slice of -1, we are able to reverse the return value.

How to get the IP address in Python

Wed, 19 Feb 2020 10:30:00 +0000

Python exposes a socket library that allows us to perform networking tasks such as getting the IP Address as well as getting the Hostname of our system.

import socket

try:
  host_name = socket.gethostname()
  host_ip = socket.gethostbyname(host_name)
  print(f"Hostname: {host_name}")
  print(f"IP : {host_ip}")
except:
  print("Could not get the IP Address or Hostname")

The above code imports the socket library and then runs a safe block of code.

We need to first get the hostname and then use that to get the IP Address.

How to Reverse a Binary Tree in Python

Tue, 18 Feb 2020 08:00:00 +0000

Reversing a Binary Tree is a common programming interview question.

By learning how to Reverse a Binary Tree in Python, you are working towards fundamental data structure algorithms commonly found in Computer Science degrees and across the industry.

If we take a look at the following Data Tree Image, we will notice a few common points.

Firstly, a binary tree simply means a tree that contains between 1 and 2 child nodes.

[Solved] Unable to Detach AWS Network Interface

Mon, 17 Feb 2020 10:37:08 +0000

You do not have permission to access the specified resource.

If you are seeing this error appears up when trying to delete or detach a Network Interface within AWS, then you need to read what the description column says, find that item and then delete that first.

We can see in this instance, we need to first delete an ELB starting with ID a4e6efd6.

Head over to the Load Balancers tab and search for that ELB:

How to delete a file in Python

Sun, 16 Feb 2020 00:57:00 +0000

A quick solution in Python

import os
os.remove("filename.txt")

The above code will delete a file in Python, it will not however delete a directory, or a directory containing files. For this we will need to explore a bit more..

Check file exists before deleting

First check if the file exists before deleting it:

import os

if os.path.exists("filename.txt"):
  os.remove("filename.txt")
else:
  print("The file doesn't exist")

Delete a directory/folder

Sometimes you may want to delete an entire folder as well:

How to safely parse JSON in Javascript

Sat, 15 Feb 2020 14:16:53 +0000

JSON stands for Javascript Object Notation and has become wildly popular to transport and store data between application, databases and more.

However, it is not always obvious that a piece of data your application is trying to use may be of type JSON, or be correctly sanitised.

Let’s take a simple Javascript function as follows:

function getNameFromJSONString(jsonString) {
    
    // Dangerous!
    json = JSON.parse(jsonString);
    
    // Dangerous again!
    return json.name;
}

What the above function does is take in a string which it believes is a stringified/serialised JSON (perhaps stored in a database), parse it back to a Javascript Object and then return an attribute called name.

Check if an HTML Checkbox is checked using Javascript

Fri, 14 Feb 2020 13:26:34 +0000

While processing forms in web development, it’s a common requirement to be able to tell if a checkbox has been checked or not.

It’s not immediately obvious though. Let’s dispell this and provide some ways to check if a checkbox is checked using Javascript.

First, we need an HTML checkbox to play around with.

<input type="checkbox" class="myCheckbox" />

Using Javascript

Using regular Javascript, we can tell if it is checked by using the following Javascript:

How to Push Docker Images to AWS ECR

Thu, 13 Feb 2020 09:11:14 +0000

Docker images are usually stored on Docker Hub, but AWS’s Elastic Container Registry can also be used. It’s a great solution and this post teaches you how to push Docker images to AWS’ Elastic Container Registry (ECR).

Create a Repository

Let’s start by using the aws-cli to create a repository.

aws ecr create-repository --repository-name myname

This command successfully creates a repository and outputs the following JSON:

How to monitor Network Traffic on Linux

Wed, 12 Feb 2020 09:42:59 +0000

There is a fantastic tool to see and monitor Bandwidth and Network Traffic on Linux.

It’s called bmon and it works out of the box.

How to Setup and Use

On Ubuntu apt-get install bmon, or in newer versions, you can also just say apt install bmon.

On Centos yum install bmon.

Once you have it installed, you can start the monitor by running bmon from the command-line.

You will be presented with multiple network interfaces (NICs).

How to Merge Javascript Objects

Tue, 11 Feb 2020 08:49:45 +0000

A Javascript Object – now just called JSON – is a collection of values and properties stored as a map.

How would you merge two or more Javascript objects together thought?

In ECMAScript 2018, the Object Spread operator will do the trick for you in no time, let’s try it out.

var jso1 = {
  "name": "John",
  "colour": "green",
};

var jso2 = {
  "name": "Andrew",
  "symbol": "arrow",
};

var merged = {...jso1, ...jso2};

The result of this would be to combine all the elements and override any newer ones where applicable.

When to use Pip3 instead of Pip in Python

Mon, 10 Feb 2020 11:39:09 +0000

If you have multiple versions of Python installed on a system, such as both Python 2.7 and Python 3.6+. Then pip will often refer to the Python2 bin, while pip3 will point to the Python3 bin.

You can easily tell what your own setup is by running the following commands in a terminal window / command-line.

$ which pip

$ which pip3

/usr/local/bin/pip3

It is also useful to know what version of Python you have on your system and where it is, as Pip is always coupled with it.

How to use Screen on Linux

Sun, 09 Feb 2020 08:36:44 +0000

Screen on Linux is a popular command-line program that lets you multiplex between interactive shells.

What that means is, you can use screen to save and restore running of commands.

`Screen` in action

The best way to test this out is to SSH into a server.

sh user@150.xx.xxx.xx

user@server:~#

At this stage, you can execute man screen to learn all the commands available to you.

You can issue a screen -list to show all screen sessions that may already be open.

Transfer a domain from Namecheap

Sat, 08 Feb 2020 14:06:08 +0000

Namecheap is a pretty good registrar. As its name says, yes, it is usually pretty cheap. I would also like to point out that I personally have nothing bad to say about Namecheap and that their service is overall pretty positive. But as with most things, there occasionally comes time to make a change. This change happens to be to transfer a domain hosted at Namecheap.

Recently I have been moving most of my domains to Cloudflare, who don’t currently offer registrations but do offer to take the domains once registered.

How to Package a Python App using Nuitka

Fri, 07 Feb 2020 08:02:54 +0000

Learn how to package a Python app in this tutorial.

For the most part, once you’ve written your Python code, you simply deploy it to a server, install the environment, grab the dependencies and you’re done.

However, there are times when you may want to provide your app to someone else and don’t want the hassle of getting them setup with all the training around making sure they have Python on their machine and can run your app.

Introduction to NPM

Thu, 06 Feb 2020 10:08:15 +0000

What is NPM?

NPM stands for Node Package Manager, and is the default way to extend your Node applications.

There are an absolute ton of packages available to install and use immediately, making NPM wildly popular for software developers.

What is Node?

Node.js, or often simply just Node, is a Javascript runtime environment that allows Javascript code to be executed outside of the web browser.

It first came about in 2009 when the creator (Ryan Dahl) took Google’s V8 Javascript Engine which powers its Chrome browser, and repurposed it. Adding in additional logic allowing it to be used independently to execute Javascript on the server.

How to create a Symbolic Link on Linux / Mac

Wed, 05 Feb 2020 10:49:20 +0000

A symbolic link – or often just sym-link – is a pointer or shortcut to where the actual file lives on a filesystem. What does it take to create a symbolic link?

The ln command actually describes it pretty well:

The manual

Why would I need a Symbolic Link?

When should you create a symbolic link is a question I am often asked.

Non-interactive git clone (ssh fingerprint prompt)

Tue, 04 Feb 2020 18:32:40 +0000

If you have ever been in the annoying situation where you had to run git clone from a server that you did not have interactive access to, such as a continuous integration/deployment box or other. Then you may have run into the dreaded Are you sure you want to continue connecting (yes/no)? dialogue.

Usually, at this stage, you would be stuck, as you need a way to tell it yes, but there’s no input!

When your Python code is much faster with PyPy

Tue, 04 Feb 2020 12:37:06 +0000

Python is a very powerful language, there are so many libraries available for it.

However, many developers will complain about its speed by comparison to certain other languages, for example, C or C++. If you’re new to Python, you might want to first check out how to learn Python programming quickly.

This is because Python is an interpreted language by design, as opposed to being compiled. Meaning that each time it executes, the instructions need to be converted right there on the spot, making for slower overall execution times. When working with Python, it’s also important to know how to setup and use the Python virtual environment for better dependency management.

What it takes to be a Platform Engineer in 2020

Mon, 03 Feb 2020 00:44:17 +0000

Platform Engineering is something that grew out of a mix of what software developers and sysadmins had been doing for years.

The only real difference is that most software these days either lives somewhere in some cloud or various services that support it do. Meaning that someone needs to design it, scale it and support it. This is not traditionally within the scope of a software engineer’s day job and requires a range of specialisms oftentimes not found with a developer’s direct focus.

Introduction to PIP – Python Package Manager

Sun, 02 Feb 2020 17:57:34 +0000

Python comes with a fully equipped package manager called PIP – which stands for the Python Package Manager.

PIP gives your python applications access to thousands of popular libraries, packages or modules for free.

What does PIP mean?

PIP is actually a recursive acronym which stands for:

PIP Installs Python
PIP Installs Packages

Before Continuing

As usual, it is recommended to do everything in a Python Virtual Environment. Making sure that you are running Python3 is also important, as Python2 has reached End of Life, and this is a welcome thing!

How to build a website quickly using PHP

Sat, 01 Feb 2020 14:14:00 +0000

PHP is a powerful scripting language created for the web.

It has come a long way since it’s initial inception in 1994.

It was originally created to build websites quickly and easily and has become a lot more than that.

While many developers and companies use PHP along with extensive and oftentimes heavy frameworks, there is no reason that you have to do that; you can build websites quickly and very easily by making use of many standard PHP functions.

How to replace all occurrences of a string in Javascript

Fri, 31 Jan 2020 12:07:00 +0000

I have pretty much resigned myself to the fact that in Javascript, there are really only two ways to do a proper search and replace.

Firstly, we need a base string to start manipulating, so let’s create our test subject:

var ourString = "This is a great string and we love it";

So now the options are as follows, replace, regular expression replace and split/join.

Javascript Replace

ourString.replace(" ", "-")

"This-is a great string and we love it"

As we can see with this method, it only replaces single occurrences in the string, which may be what you are trying to achieve, but it certainly wasn’t for this case!

How to exit Vim

Thu, 30 Jan 2020 11:32:19 +0000

If only I had a dollar for every time I saw someone sitting at their computer, trying for the life of them to exit vim

TLDR;

Vim or sometimes just vi is a command-line (cli) application that lets you edit documents. It’s massively popular and my personal go-to editor when I’m on a Linux box. Particularly if I’m editing remote files on a webserver or other.

How to Setup and Use the Python Virtual Environment

Tue, 28 Jan 2020 09:23:42 +0000

Python is a fantastic language that continues to help so many businesses and individuals. It offers readable syntax to get started, yet extensive amounts of control and flexibility to move into the more advanced areas of software engineering. Python the number one choice for many because it is packed with the power of unparalleled libraries, it recommended to run them through a python virtual environment.

Introducing the Hetzner Cloud

Mon, 27 Jan 2020 15:52:00 +0000

I could honestly not tell you how many hosting providers I’ve tried over the past 15 years. Probably more than 30, 40… Easily!

Today I would like to introduce you to the Hetzner Cloud. No, I do not work for Hetzner, or have any affiliation to them whatsoever, this is purely a sharing exercise as I have noticed that when I speak of them in my professional capacity, most colleagues don’t know about them. Not sure why, as most people know about Digital Ocean and a few others, but with the same token, these people don’t tend to know about Linode, Vultr, OVH, and some others. Most people within my profession only know and care about the big players, such as AWS, GCP and Azure.

Multiprocessing in Python3

Tue, 14 Jan 2020 14:13:04 +0000

import multiprocessing

def runner(k):
  print(k)

processes = []
for i in range(10):
  p = multiprocessing.Process(target=runner, args=(i,))
  processes.append(p)
  p.start()

for j in range(len(processes)):
  processes[j].join()

Now that you have the code; let’s explain:

Import the multiprocessing library

import multiprocessing

Define the function that will run each time a process is executed

def runner(k):
  print(k)

Keep track of all the processes

processes = []

How many processes do you want to run?

for i in range(10):

Send some arguments to the running function

How to Install MongoDB on Mac

Sat, 04 Jan 2020 23:55:58 +0000

You can use Homebrew to install MongoDB on a Mac.

For ages you were able to simply do:

brew install mongodb, but more recently, that has stopped working as it was removed from homebrew-core. Now, you need to do it as follows:

brew services stop mongodb
brew uninstall mongodb

brew tap mongodb/brew
brew install mongodb-community
brew services start mongodb-community

You can read more about it here if you’d like.

The Best Note Taking Apps

Fri, 20 Dec 2019 09:09:50 +0000

We’re all using a Note Taking App these days, they’re incredibly useful and come jam packed with loads of features. But which ones shine out from the rest and which should you use in 2019?

Among the many tens to hundreds of possible candidates, I have chosen the seemingly obvious top 5 to explore in this post. These were initially chosen from my own experience having used many over the past few years to find the ultimate single Note Taking app to conquer all others.

How to Delete large amount of files in directory

Mon, 09 Dec 2019 13:29:51 +0000

So you have clearly got a very large amount of files!

If you issue the conventional rm -rf * within the directory, you will get an error -bash: /bin/rm: Argument list too long.

You can still easily remove these files, just make sure to use the find command instead!

Solution:

find . -type f -delete

How to Merge multiple files, removing duplicate values

Mon, 25 Nov 2019 17:51:56 +0000

If you have multiple files and you want to remove duplicate values from, while creating a single file.

File1 (one.txt):

File2 (two.txt):

As you can see, the two files contain some duplicates. You can easily remove these using the following command:

sort -u one.txt two.txt

This will output:

You can as easily pipe this into a third file as follows:

Unable to delete an AWS Internet Gateway

Fri, 22 Nov 2019 13:16:31 +0000

So you need to delete an AWS Internet Gateway, sounds good.

You navigate to the VPC (Virtual Private Cloud) dashboard and go to Internet Gateways.

At this stage you select “Actions” and choose the “Detach VPC” option.

In a perfect world, this would return a “success” and the IG would be deleted.

But sometimes this isn’t the case and you have to do a little more.

How Distributed Applications Work

Mon, 29 Jul 2019 14:14:56 +0000

Distributed Applications come in a wide range of sizes, usages and resource availabilities.

What is a Distributed Application?

A perfect example of a Distributed Application is a multiple node database application such as Cassandra, HBase or Serengeti. These applications make use of multiple instances of themselves to be able to address vast amounts of data are stored across many networked computer systems.

Why Artificial Intelligence (AI) won’t necessarily take your job

Tue, 09 Jul 2019 08:34:27 +0000

Artificial Intelligence, or simply AI these days, is when computers are able to perform tasks that humans would otherwise do.

While this is incredibly exciting for many, it can be absolutely terrifying for others. Specifically those in roles that AI tends to current target.

After all, losing your bread and butter to a computer just seems wrong, but the reality of it is that some roles are already being swapped out for the lesser emotional, more rapidly replicable being of the twenty first century.

The difference between ‘git fetch’ and ‘git pull’

Mon, 08 Jul 2019 18:30:26 +0000

Git Pull vs Fetch

Many of us take a look at git fetch and git pull and believe them to do the exact same thing! This is just not true.

So what exactly is the difference and when should you use one over the other?

The Difference Between Pull and Fetch

<p class="schema-faq-answer">
  The <code>fetch</code> command goes to the remote repository and gets the latest information about the branch, commits, references (tags) and all the file objects. This is then returned to the local git instance so that it knows what to do when you want to issue a <code>merge</code>.
</p>

<p class="schema-faq-answer">
  The <code>pull</code> command essentially does a <code>git fetch</code> and a <code>git merge</code> on the respective branch.
</p>

Roundup

So when would you ever use git fetch then? Well, it’s for when you want to get all the information about changes without merging those changes into your local branch and overwriting your local working copy. It is also very useful for when you want to get the meta about a tag without pulling that tag’s reference data back over your local branch.

7 Ways to Make Money Online from Home

Mon, 08 Jul 2019 13:39:50 +0000

1. Create a website / blog

There are numerous ways to make money when you create a website or blog. It’s really cheap and easy to do these days as well, with so many available options, some are even free. But how do you monetise your new online presence once you have created something?

There are a few obvious ways, which include:

Sell things on your website
Advertising on your website

These are probably the most common ways to make money online from home for almost free.

Investigation of insider attacks with computer forensics

Sun, 07 Oct 2018 12:22:38 +0000

Cyber-attacks do not always originate from outside of the target organisation. Veritably around twenty-five percent of all data breaches occur from the inside, from employees or trusted individuals within the organisation (TechBeacon, 2018).

Employees that have access to internal records, intellectual property or intramural trade secrets need to be watched as closely as any external party or connection should be.

Why employees are a risk

Employees can trigger internal cyber-attacks, steal intellectual property or even publicly release internal affairs and private information for a number of reasons, which could include:

Squid Proxy behind a Load Balancer on AWS

Thu, 04 Oct 2018 11:39:39 +0000

Squid is a proxy software that allows a computer without internet access to proxy through another computer that does have internet access.

Squid is very easy to get setup and the computer that needs internet just needs to specify environment variables called HTTP_PROXY and HTTPS_PROXY which have the value of http://squid.ip.address:3128/

The complication comes in where you need a Squid instance (sitting on an EC2) to sit behind an AWS load balancer. This is usually done for a number of reasons, such as service redundancy, uptime guarantees or even mitigating against maintenance schedules.

How to install a Ruby Gem without Root on a Mac

Mon, 01 Oct 2018 11:38:11 +0000

Gems are little packaged Ruby applications that allow you to extend the ecosystem and reuse countless online sources.

If you don’t have Root on your Mac (work at a large company?) but you still want to use a Gem or two, then you will usually get the following error when attempting to install:

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

This is incredible annoying, but something you can’t avoid. So better find a workaround and move on!

The dark truth behind Advertising on the internet

Mon, 01 Oct 2018 09:56:13 +0000

The story

Steve has a website which sells carpets in London.

Steve’s carpet business has been doing really well and Peter has recently noticed just how well. Peter decides to get into the same business and decides to build a website too.

Peter’s website is soon complete and he has a little stock to get started.. but nobody visits his website. So he decides to take out some online ads.

International hosting governments and forensic email cases

Sun, 30 Sep 2018 21:59:03 +0000

Cyber forensics is hard, but it is even harder when servers are hosted in different geographical locations and an investigation needs all localities to cooperate and hand over every part of the data consistently.

This is primarily due to privacy laws that each region may apply or carry out in differing ways.

Multiple regions

Even if a compilation can source multiple regions data; dealing with international governments could mean prolonged wait times, unfamiliar processes to follow or even citizens of those regions withholding data due to privacy rights within that region.

When to give up on your startup/product

Fri, 28 Sep 2018 11:46:22 +0000

One of the hardest things you can do after trying to get a startup or product off the ground is to simply give up and call it a day.

After all, you’ve put an awful lot of blood, sweat and tears into it, and you have probably done this for months, if not even years!

As a life-long software developer, I’ve always had side projects going, some from small ideas to others that I have truly invested a lot of time and money into. We all seem to fall down this same path and who doesn’t want their own company, doing exactly what they want to do?

Just SSH to my Jump Box!

Wed, 26 Sep 2018 22:14:23 +0000

I am a professional software engineer and do an absolute ton of devops work as well.

I’ve actually never been hired into devops roles as I always go in as a programmer, but I also always end up doing devops as well for various reasons.

What tasks?

These usually include things like:

I like to get my code running on infrastructure as soon as possible for Proof of Concepts (POCs) and the like.
I’m often one of the first people in the team, or am part of starting the project.
I have a good grasp on the system admin side of things and like to get my hands dirty.
I made the first prototypes of the software so like to get all the other parts up so that new joiners have a good understanding of how things work together.

One of the things I have found about getting this all going each time is that I end up with usually quite a lot of rapidly changing Compute machines (EC2s) and other services. It is perfectly fine for me to login and get the latest IPs to SSH to, or keep a local config, but as soon as I have a team that needs to start using them, connecting to things or getting onto boxes to made changes then this doesn’t really work all that well.

Counting in Python using a list

Tue, 25 Sep 2018 13:24:10 +0000

So before we begin, let me just tell you that this is a pretty useless thing to do.. But I was playing around with it while waiting for a C++ project to finish compiling, so why not!

The code (click here for the Gist):

magic = 0x616f-0x414f

numbers = [
    (magic/0x186A0),
    (magic/0x3E8/8),
    (magic/0x3E8/4),
    (magic/0o1534-7),
    (magic/0x3E8/2),
    (magic/0o2534-1),
    (magic/0o2544),
    (magic/0o075/19),
    (magic/0o064/19),
    (magic/0o1654)
]

i = c = numbers[0]

while True:
    print('%d%d' % (c, round(numbers[int(i)])))
    i += 1
    if i>len(numbers)-1:
        i = 0
        c += 1

If you ran it, it would look like this!

Show the desktop’s image name on a Mac

Sun, 23 Sep 2018 16:50:40 +0000

Sometimes you just need to know where that image shown on your desktop is stored!

For this, there is a simple but effective line of text you can pop into your terminal.

defaults write com.apple.dock desktop-picture-show-debug-text -bool TRUE;killall Dock

This will render the image’s location pathname and image name over the desktop background image.

When you’re complete and you want to disable that over render of the image name, then simply type:

Network Forensics Concerns around GDPR

Sun, 23 Sep 2018 16:39:47 +0000

In Cyber Forensic there are a vast array of tools that are used throughout most investigations, however, not all jurisdictions allow or even agree to the usage of some of them. This is mainly due to each specific geographical region’s view on their citizens right to privacy.

Some of the tools and tactics to collecting evidence are therefore questionable and raise specific concerns in this matter.

During the evidence collection process there are many things to consider when it comes to data being transferred over a network.

A look into Future Developments in Operating Systems from a Cyber Forensics Investigator

Sun, 16 Sep 2018 11:51:55 +0000

Operating systems (OS) really have come a long way since the very first one was created by General Motors in 1956 (WIHT, 2017) to run on an IBM mainframe.

Since then, there have been countless attempts at popularising OS?s and a few companies have truly stood the test of time.

Among these the Windows OS, MacOS and Linux OS are the most notable with the highest market share and global penetration.

Comparing Interface Types in Cyber Forensics

Sun, 02 Sep 2018 19:56:16 +0000

In digital and cyber forensics, there are three main types of categories when it comes to forensic tooling. They can be considered as:

Graphical User Interfaces (GUI?s)
Interactive Text-based Consoles
Command-line interfaces (CLI?s)

Of these, the main competitors are really just GUIs and CLIs as they certainly differentiate most from one another.

They both have their strengths and reasons to be used, of which neither should be discounted.

Many people like to use the GUI version of an application, as it allows them to focus on the task at hand that may extend between a range of activities and doesn?t require them to remember command line arguments and other such distractions. Essentially, getting straight to the point and focusing on retrieving the necessary evidence to place into a report in order to complete the investigation at hand.

Cyber Forensic Investigative Reports

Sun, 26 Aug 2018 11:24:54 +0000

Investigations are not proven in a jurisdiction until a detailed forensic report is created and presented to a judge or jury who can take it to the next level. Presenting digital evidence should be laid out that it is not overly technical in order for all parties to fully understand and interpret in its arrangement, yet still goes into absolute detail to express all the intricacies of an investigation and its extrication.

Altering Computer Evidence

Sun, 19 Aug 2018 16:28:38 +0000

Ever since it has been possible for humans to operate computers, some have used it to perform criminal activities.

Part of a cybercriminal’s gameplay is to cover up or otherwise alter digital evidence in one form or another.

There are many reasons why cybercriminals may try to alter computer evidence; these could be any of the following:

Cover their traces
The most obvious reason is to simply cover up that the fact that an attacker was around and where the attack came from.
Shift the blame
Covering evidence or planting alternative evidence could shift the blame and make it appear as though another attacker, group or country was to blame for the attack.
Cover up a wider plan
Sometimes an attack is simply part of a larger, more coordinated attack. Covering up evidence at this point would be crucial in order to complete the greater plan.

Every time a computer is used, logged into, or attacked locally or remotely, traces of evidence (often called “logs”) are stored which can lead back to identify the operative; potentially showing where they connected from and what group of exact activities they performed (Kassner, 2015).

Connection broken by ‘SSLError(SSLError(1, ‘[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:777)’

Thu, 26 Jul 2018 21:22:25 +0000

This happens when your machine does not have the correct certificate bundle to access the Pypi repository, or you are behind a corporate proxy that just loves to block everything!

An easy way to get around this is to edit (or create) a local pip.conf file under your home directory:

~/.pip/pip.conf

Put the following in:

[global]

index-url = http://mirrors.aliyun.com/pypi/simple/
trusted-host = mirrors.aliyun.com

As you can see, we have changed the download location to a mirror that doesn’t use HTTPS, so there will be no certificate issues.

Can’t pull a Git branch because of merge conflicts?

Wed, 27 Jun 2018 17:42:49 +0000

Sometimes you need to pull a remote branch and want to accept all their commits (and history) and override your own repository.

It’s quite simple if you do a pull, don’t care about unrelated histories and accept all their code when there’s a conflict.

git pull upstream master  --allow-unrelated-histories  -s recursive -X theirs

Then simply push to your own remote and you’re done!

Software development processes

Sun, 13 May 2018 13:36:17 +0000

Introduction to Software Development Processes

Gabry defines the Software Development Methodology to be a set of related activities that lead to the production of the software (2017).

While this is the simplest concept of the processes, there are many formalised industry best practises in operation today; some of these include Rational Unified Process (RUP), OPEN, eXtreme Programming, Scrum, RWSP, DSDM and more.

A****?software development scenario****

Though I have worked under a range of these processes, I have found the Scrum methodology to be the best performing in most workplaces.

Approaches to software reuse

Sun, 13 May 2018 13:31:02 +0000

Introduction to Software Reuse

Software reuse is the process of creating software from antecedent and extant components.

There are a range of approaches that can be taken when following a reuse pattern, these can usually be grouped into one of the following abstractions:

Class Libraries
Reusable Components
Application Frameworks
Patterns / Service Oriented Architecture (SOA)

There are many benefits in taking up software reuse (SelectBS, n.d.). These include increased software productivity, shorter development times, improved interoperability, recuded costs and usually higher output quality to name a few.

Get the output of an application logged in the terminal

Mon, 16 Apr 2018 14:51:26 +0000

Just a quick note:

You are probably looking for a Linux command called `dtrace`.

If you’re on a mac then you are probably looking for `dtruss`.

Agile as a Software Development Process

Sat, 24 Mar 2018 12:33:40 +0000

Waterfall and Agile are by far the most commonly used software development processes, however, within them, there are many different styles of software development used in the management of software development projects.

While each has their own advantages and disadvantages, we will focus on Agile as it has rapidly grown in popularity over the past few years and is widely accepted throughout the software development discipline and across a wide range of industries of all sizes.

Big Data Security and Privacy Issues

Fri, 02 Mar 2018 15:03:56 +0000

Big Data shares what is commonly termed the V properties or characteristics such as Velocity, Volume and Variety which are amongst the most typical or frequently repeated.

Taking into account security issues and privacy implications with such large datasets is a challenging ordeal that needs a repeatable framework to cover all areas.

Volume is with little to no doubt the most highly targeted characteristic as the expression Big Data fundamentally factors a voluminous amount of information or data that needs to be processed (McCafferty, 2013).

How to delete/revert a Git commit

Fri, 02 Mar 2018 12:59:17 +0000

You’ve just pushed something to a Git repository and you immediately regret it!

Run git log to see what the commit id was:

git log

Take the first 7 characters of the commit SHA id and do the following:

git revert <commit_id>
git push --force

But if you’re like me and your problem was because of a merge conflict that you tried to resolve and clearly failed at, but still had the balls to push to the repo before wishing you hadn’t; you can still recover this terrible moment in your life by undoing the merge request itself.

[Solved] Pip: There was a problem confirming the ssl certificate

Mon, 26 Feb 2018 12:52:39 +0000

If you ever get the following error when trying to install a Pip module under Python:

Could not fetch URL https://pypi.python.org/simple/****/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:777) - skipping

Then an easy way to get around it is by adding the trusted-host flag to your commandline argument as follows:

--trusted-host pypi.python.org

So your final command may look something like this:

pip install some_module  --trusted-host pypi.python.org

How to Learn Python Programming Quickly

Thu, 22 Feb 2018 10:56:15 +0000

So you want to learn to program in Python and you don’t have a lot of time?

That’s okay! Once you grasp some of the key concepts and ways of thinking, it will all come to you.

So let’s get going now, shall we?

What is Python?

Python is a high-level, interpreted, object-oriented programming language with dynamic semantics used for general-purpose programming. It was created by Guido van Rossum and first released in 1991.

NoSQL Pandas Dataframes

Fri, 16 Feb 2018 17:35:38 +0000

Pandas Dataframes are simply a table with some rows (McKinney, 2015) and many additional features built right in to make data scientists lives much easier.

What are NoSQL Pandas dataframes?

Pandas is an open source Python library that provides high performance yet easy to use data structures and data analysis tools (Pandas, 2018).

Dataframes are two-dimensional size-mutable, potentially heterogeneous tabular data structure with labeled axes. They can be thought of as dictionary type containers for Series objects (PandasDocs, 2018); they are also the primary data structure used in Pandas.

Relational (SQL) vs NoSQL Database Models

Sun, 04 Feb 2018 11:43:05 +0000

The Relational (SQL) database has been a central piece to businesses since the 1970s when they first had their claim to fame.

Experts say that the world?s data is doubling every two years (Gajani, 2017) and this is simply something that traditional relational databases cannot manage with their architectural inner workings and scalability concerns.

Netflix Hadoop Big Data Marketing Use Case

Sun, 28 Jan 2018 13:33:49 +0000

Netflix is a video streaming service that has a wealth of information about their user base likes, dislikes, general consumer habits, retention lengths and much more.

Netflix uses their big data to commission original programming content that it knows will succeed and be accepted in relevant published markets (O?Neill, 2016).

They perform various A/B tests to determine which variant of similar things perform higher, for example, when showing cover images for series or movies, they will at random show alternative images to determine which proves more reactive from their user base.

Using Hadoop to manage Dark Data

Fri, 19 Jan 2018 17:18:45 +0000

Dark Data is the biggest piece of the pie (Datumize , n.d.) when it comes to Big Data and what lies beneath huge datasets of collected information.

IBM has stated in a report that over 80 percent of all data is dark and unstructured, meaning that it is simply too much data to process, analyse or unlock valuable information from.

This data is termed Dark Data and is mostly unstructured and oftentimes missing or incomplete, which leaves a lot of potential for solutions to be built around high volume analytics and processing.

An Introduction to Client-Server Systems

Sun, 10 Dec 2017 14:27:59 +0000

A client-server architecture/system is one where the server maintains all models of the backend datasets and business logic around taking and providing information to fulfill a service request from a client which in turn shows the representation thereof.

The client/server model has quickly grown in popularity throughout the 1990s and today serves as a favoured choice for most organisations? (Subramanian, Lacity, 1997) operations.

When to use FLUSH PRIVILEGES in MySQL

Wed, 06 Dec 2017 21:09:39 +0000

So if you’ve ever created users and given them specific permissions from with SQL or the commandline, you will be familiar with a statement called FLUSH PRIVILEGES.

It is said that if you create a new user, or alter than user, you should run FLUSH PRIVILEGES in order for the MySQL Engine’s Session to take the change into immediate effect.

But what about if you GRANTed or REVOKEd a permission? Do you still need to use it?

MySQL Community Server MSI Installer Hangs on Windows 10

Wed, 06 Dec 2017 00:30:57 +0000

I was trying to install MySQL Community Server for Windows 10 using the standard .MSI installer provded from the MySQL website and the installer just hung, saying that there was 3 seconds remaining.

About half an hour later, it still said “3 seconds remaining”.

It turned out that you have to run cmd (commandline) as Administrator:

Press Windows Key (Super), type “cmd”, right click on “Command Prompt” and select “Run as administrator”.

Android device supports x86, but APK only supports Arm

Mon, 04 Dec 2017 10:26:50 +0000

I get this error quite a lot when trying to deploy an Android APK to an emulator.

“Device supports x86_64, x86, but APK only support , all, armeabi-v7a”

The good thing is that it is actually a very easy thing to fix.

While doing development you can simply change the Build Variant target.

How do you do that?

Click “View” -> “Tool Window” -> “Build Variants”

Weird Dialog Boxes

Thu, 30 Nov 2017 13:58:25 +0000

Adobe Setup setup?

Got this one while using Chrome, it complains about Safari?

What a load of bullshit!

Really?

Very handy tips screen!

ERROR: NO ERROR!

A bit on SQL Standards

Sun, 12 Nov 2017 14:07:47 +0000

SQL (Structured Query Language) for relational databases was maintained and standardised by the American National Standards Institute (ANSI) and the International Organisation for Standardisation (ISO) which is affiliated with the International Electrotechnical Commission (IEC).

When a new SQL standard is published by these organisations it is outlined on the ISO website and available for everyone to both reference and use as required.

A Brief Talk on Databases

Sun, 29 Oct 2017 00:28:10 +0000

Databases have been around since ancient times, when elaborate database systems were deployed by governments, hospitals and organisations to keep track of vast amounts of information; but only until around the 1960s did computerised databases start to take shape and become cost effective for private organisations to start using (Quickbase, n.d.).

I have used countless databases over my career to reliably store and retrieve many sizes of information, from a small collection of less than ten items of data to terabytes worth of hundred of billions of data points spread across clusters of machines around the world.

Cloud Computing – The Refute

Sun, 24 Sep 2017 18:49:17 +0000

Cloud is great, but when you know what you are doing, think about alternatives (Blippex, 2013).

What is Cloud?

“The cloud” is a term given to pay as you go – or pay monthly – off premises computing services that provide either hosting or storage to it?s user base. These services are created, maintained and wholly operated by a cloud computing provider.

Auditing Organisational Information Systems – Security

Sun, 17 Sep 2017 01:10:28 +0000

Auditing an organisation?s information systems is a vital part of operating a business at any decent scale. Particularly from a security standpoint (Mohamed ElBorno, n.d.).

Information systems have many different facets and each organisation operates slightly differently, so while auditing can be handled the same on general shared traits, more bespoke business units and organisational structures should be taken into account when designing a well thought out auditing system that fully guarantees the security of an organisation?s systems.

Biometric Technology

Sun, 17 Sep 2017 01:09:52 +0000

What is Biometric Technology?

Biometric verification is any means by which a person can be uniquely identified by evaluating one or more distinguishing biological traits (Margaret Rouse, n.d.)

Such recognition usually falls into one of the main categories such as:

The above are the verification patterns which various technologies are built around in order to create working application use cases for larger security concerns.

Copyright Compensation in the Internet Age

Sat, 09 Sep 2017 17:08:09 +0000

The original conception of copyright in 1710 (Craig Joyce, n.d.) was that it usually covers only the expression of a particular idea and not the idea itself, but this was a very long time ago, before the challenges of a digital society.

Since then, copyright has had to encompass a wide variety of extended property far removed from it?s original case studies that were available at the time.

Controlling employee digital access

Sun, 03 Sep 2017 11:55:35 +0000

Organisations of all sizes have taken to controlling what their employees can access in order to conserve computing resources, keep their employees focused 100 percent on the work they were hired to do and to make sure employees performance is high and as productive as possible (Cyberoam, n.d.).

However, keeping employees motivated and productive is not as simple as simply restricting specific access to internet resources and computer controls.

Electronic monitoring in the workplace

Sun, 03 Sep 2017 11:54:37 +0000

Electronic monitoring is not a new thing, nor one that only affects the workplace. From closed circuit television (CCTV) in stores and down many streets, to similar surveillance in offices everywhere, we are constantly being monitored in all aspects of our lives.

Why and how employers are monitoring employees

Many employers and organisations tend to perform similar tactics when it comes to monitoring (Emma Anderson, 2014), but I would like to focus on my current and previous employer in order to draw a common ground and paint a picture as to where and how we as employees are being electronically monitored.

The Therac-25 Case Study – What Actually Happened?

Sun, 27 Aug 2017 11:37:13 +0000

The Therac-25 was a computerised medical technology radiation therapy machine produced by Atomic Energy of Canada Limited (AECL) in 1982.

Between 1985 and 1987, it was involved in at least six patients deaths due to incorrect radiation doses because of computer software related failure.

When the error was first seen, it was thought to be a hardware problem with the microswitches.

Your Responsibilities as an IT Professional

Sun, 27 Aug 2017 11:35:05 +0000

As an IT professional it is extremely important to make sure that you do not take advantage of your position on being able to introduce certain skewed characteristics into a computing system in order to gain unfair advantage to your company or client?s business.

This is seen as unethical and in many cases can also be illegal.

New capabilities with technology

Wed, 23 Aug 2017 20:30:02 +0000

Computing technology has undoubtedly had some very prominent impact on society at large.

Of the almost countless capabilities that it has brought us, the following five core capabilities are without a doubt at the top of any compiled list on the subject:

Being able to store an unlimited amount of data is one of the main capabilities that we will expand upon and explore in a bit more detail as it provides innumerable offsprings into technological advancements and data insights generally for a wide range of applications and technologies in almost all sub-industries.

The Printing Press – Technology’s impact on society

Wed, 23 Aug 2017 20:09:47 +0000

It’s important to first define what the term “technology” means.

Technology is “the application of scientific knowledge for practical purposes, especially in industry.” (Oxford Dictionary, n.d.)

The term is not reserved for computing systems, but for any field of engineering or applied sciences.

The printing press has been one of the most important inventions in history and would definitely classify as being within the top few technological enhancements of all time.

Google Abuses Search Dominance in the European Union

Wed, 23 Aug 2017 20:08:26 +0000

The EU Commission found that Google has been favouring their very own shopping service while demoting those of their rivals as well as the placement of how they are seen in search results online.

This is favoritism or preferential treatment which makes it unethical, regardless of sustainability thereof.

This is a negative thing as a world-wide monopoly of this magnitude should not be allowed to occur at all.

Understanding the Risks of Commercial off-the-shelf software (COTS)

Sat, 08 Jul 2017 22:18:48 +0000

Commercial off-the-shelf (COTS) software can be an attractive buy in for many companies when it comes to:

It can seem very attractive at first to jump into a COTS solution, but there are many things to take into account that can make it a less than ideal option. This is where analysing potential software reuse risks is highly recommended and will make the difference between an overall cost saving as initially expected, compared to a failed attempt where the result ends up costing significantly more and the project runs over all checkpoints as well as completion dates.

Identifying Risks in Software Engineering

Wed, 28 Jun 2017 00:44:21 +0000

In Software Engineering it is absolutely paramount to identify all risks that may arise in a given project or grouping of tasks. Without doing the aforementioned, a project can quickly unravel and become disjointed and inherently fall apart.

It is very important to be able to identify risks and act on them appropriately and in a timely manner (Pressman,1997).

Software engineering challenges in the 21st century

Sun, 04 Jun 2017 18:23:20 +0000

Software Engineering covers not only the technical aspects of building software systems, but also management issues, such as directing programming teams, scheduling, and budgeting. (Webopedia, n.d.)

The world of software has exploded since it’s humble beginnings in the mid 1940’s.

Over the next 30 years the industry focused primarily on cost effective hardware manufacturing and software was undertaken as a second measure, but there were no real methodologies to creating robust, reusable software components. (Computer Hope, 2017)

Computer Memory – The Breakdown

Mon, 26 Dec 2016 19:50:38 +0000

Storage devices have come a long way in an extremely short amount of time; given how much they have changed from just my personal knowledge alone. I still remember using an IBM PC XT 286 with 640KB of RAM and a 64KB ROM to using services provided by companies over the past few years such as Backblaze who are building out 60 Drive 480TB Storage Servers accessible from anywhere.

There are two primary types of storage topologies. Volatile Memory and Non-Volatile Memory.

Current Trends in Computing

Sun, 18 Dec 2016 07:32:36 +0000

Academic integrity in a cultural context

Sun, 11 Dec 2016 12:05:08 +0000

In academia it is vitally important to backup your own thoughts and ideas by using previously written authoritative papers and articles in reference.

This helps provide you more credibility as well as proof of what you’re saying actually makes sense and falls in line with previous extensive research that has been done on the subject. It also helps to build upon others so as to not have to “reinvent the wheel” each and every time. “Standing on the shoulders of giants” could potentially be the greatest lesson learned in progressing an industry and the concept of intellectual property is often not widely known and dealt with correctly.

How to get more traffic to your blog

Thu, 03 Sep 2015 16:44:26 +0000

If there’s only one thing that keeps website owners up at night, it’s thinking about the next wave of traffic that they aren’t yet getting.

Without decent amounts of traffic your website isn’t really doing all that much – regardless of what fantastic theme or design you may think you have.

and gain a more popular website bustling with loads of daily visitors**
**

The obvious method to get more visitors is to go to where everyone else on the internet is most of the time. That would probably be one of the many social networks, such as Facebook, Twitter, Pinterest etc.

How big is Amazon S3 really?

Tue, 01 Sep 2015 14:03:39 +0000

Amazon’s Simple Storage Service, or simply S3 for short, is a product designed for storing objects (or files are most people know them) in their proprietary cloud hosting (AWS).

Since S3 was first released on March 14th of 2006, it has gained amazing amounts of popularity online, particularly from web and software developers.

It’s quite interesting to know what S3 really is under the hood and how large it has become.

3 Things you should be tracking with your analytics software

Fri, 28 Aug 2015 10:06:20 +0000

What should we be tracking?

This is a question we get asked quite a often – mainly by new customers as well as people who aren’t certain if what they’re looking at adds any value to their daily business time usage.

If you’ve ever used an analytics tool, you will identify with how addictive it can be to watch the traffic coming in, see where everyone visitor is from and what they are looking at as it happens in realtime.

11 of the Best Google Analytics Alternatives

Wed, 29 Jul 2015 08:59:55 +0000

So most webmasters know about Google Analytics and have probably used it to some degree, but did you know that there are some pretty good alternatives out there, some even better than the all-famous Google Analytics.

We have decided to do a roundup and show off some of our favourites – obviously, we favour Statvoo as we created it, so it’s clearly better ;).

Clicky

Clicky focuses on keeping things simple and lets you see the stats that matter as they come in.
Setup is simple and involves a snippet of custom code that you add to your website.

503 Service Unavailable: Back-end server is at capacity

Tue, 28 Jul 2015 08:58:42 +0000

The Web server (running the Web site) is currently unable to handle the HTTP request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. Some servers in this state may also simply refuse the socket connection, in which case a different error may be generated because the socket creation timed out.

Fixing 503 errors

User Testing and Feedback?

Thu, 07 May 2015 14:52:37 +0000

So now you have a website, you use it and love it, but does everybody else?

There are many tools out there that allow you to do User Acceptance Testing and provide Feedback from real users, but what are the options?

Here are some options we have found that may be of interest.

UserTesting.com UserTesting.com provides on-demand usability testing.
Uxeria.com Your solution for rapid user testing. Users recording in 48 hours.

Date ranges are the key to a better index

Wed, 14 Jan 2015 16:09:15 +0000

Since AO Analytics originally went live in February 2013, we have been doing focused around individual time based reporting, it worked well and we were able to sort through indexes without doing full table scans.

After much feedback from our users as well as data usage patterns we made the decision to move to date ranges.

This replaced our entire retrieval algorithm and therefore copious amounts of work had to go into regression of backward compatibility while introducing the new way of moving forward with the overall system.

Track your Alexa Rank History

Wed, 14 Jan 2015 16:03:10 +0000

The Alexa Rank is a way of determining a website’s popularity. ?Alexa.com are in the game of Internet popularity ranking and for quite a long time now have been doing a very good job of it.

They have a system where the most visited website on the planet is rated as #1 and the second is #2 and so on.

If your site is within the top 100,000 alexa rank it is watched more closely and general usage statistics are calculated about it.

SSL Encryption – Update

Wed, 14 Jan 2015 16:00:53 +0000

We have just rolled out SSL encrytion on Statvoo which means:

Event data is saved over a secure channel
Authentication is done automatically
All our user’s login information can not be cached over proxies
Https sites can now use the service as well

Why Website Analytics Is So Important These Days

Wed, 14 Jan 2015 15:59:12 +0000

The web has come a long way since Tim Berners-Lee, a British scientist at CERN, “invented” the World Wide Web (WWW) in 1989.

Above is the very first Web Server with the classic label on the front “This machine is a server, DO NOT POWER DOWN!!”. Which has become an object of many nerds interests as with it being the very first web server, it is quite an interesting machine to study – not that it is available to play around with, but just because of the nerd value it adds.
Since these days the web has become a lot more intricate and we have found ourselves using the internet for many things and on many types of devices.

Create daterange array of missing dates

Thu, 20 Feb 2014 09:33:45 +0000

<?php

//fromDate
2014 - 01 - 22
//toDate
2014 - 02 - 20
//$arr
Array(
    [0] = & gt;
    Array(
        [ISO_DATE] = & gt;
        2014 - 02 - 18[DAY_SUM_AMOUNT] = & gt;
        3000[DAY_SUM_VOLUME] = & gt;
        2[CONVERSION_PCT] = & gt;
        100
    )

    [1] = & gt;
    Array(
        [ISO_DATE] = & gt;
        2014 - 02 - 19[DAY_SUM_AMOUNT] = & gt;
        4000[DAY_SUM_VOLUME] = & gt;
        1[CONVERSION_PCT] = & gt;
        100
    )

)

//codetime
function createDateRangeArray($strDateFrom, $strDateTo)
{
    $aryRange = array();
    $iDateFrom = mktime(1, 0, 0, substr($strDateFrom, 5, 2) , substr($strDateFrom, 8, 2) , substr($strDateFrom, 0, 4));
    $iDateTo = mktime(1, 0, 0, substr($strDateTo, 5, 2) , substr($strDateTo, 8, 2) , substr($strDateTo, 0, 4));
    if ($iDateTo & gt; = $iDateFrom)
    {
        array_push($aryRange, date('Y-m-d', $iDateFrom)); // first entry
        while ($iDateFrom & lt;
        $iDateTo)
        {
            $iDateFrom += 86400; // add 24 hours array_push($aryRange,date('Y-m-d',$iDateFrom)); } } return $aryRange; } function recursive_array_search($needle,$haystack) { foreach($haystack as $key=>$value) {
            $current_key = $key;
            if ($needle === $value or (is_array($value) & amp; & amp;
            recursive_array_search($needle, $value) !== false))
            {
                return $current_key;
            }
        }
        return false;
    }

    $dates = createDateRangeArray($fromDate, $toDate);
    $arr2 = array();
    foreach ($dates as $date)
    {
        $inArr = recursive_array_search($date, $arr);
        if ($inArr !== false)
        {
            array_push($arr2, $arr[$inArr]);
        }
        else
        {
            array_push($arr2, array(
                "ISO_DATE" = & gt;
                $date,
                "DAY_SUM_AMOUNT" = & gt;
                0,
                "DAY_SUM_VOLUME" = & gt;
                0,
                "CONVERSION_PCT" = & gt;
                0
            ));
        }
    }
    $arr = $arr2;

Speedtest on Ubuntu Server (commandline)

Wed, 19 Feb 2014 09:42:39 +0000

Using the speedtest-cli is easy and very useful. You run it as follows:

wget -O speedtest-cli https://raw.github.com/sivel/speedtest-cli/master/speedtest_cli.py
chmod +x speedtest-cli
./speedtest-cli

URL GET vars to PHP Array

Tue, 14 May 2013 10:52:33 +0000

Sometimes you will need to retrieve the GET variables passed into the current page URI or you will have a URL string to work from which contains certain GET variables, the below method helps a lot to convert them into an array which you can easily manipulate later.

$url = $_SERVER["REQUEST_URI"];
parse_str(parse_url($url, PHP_URL_QUERY), $array);

$array is now an array of all the GET variables in the URL.

Alternatively you can pass a URI string in place of the $_SERVER[“REQUEST_URI”] by replacing the $url variable with something else.

python "AttributeError: ZipFile instance has no attribute ‘exit"

Wed, 08 May 2013 10:28:57 +0000

This is actually a very easy error to fix, eventhough off the bat it seems a lot more involved.

You probably have syntax something like this:

with zipfile.ZipFile(wr_zip) as zipfd:
  extract(zipfd, wr_csv, wr_csv)

So instead we will change it to this:

zipfd = zipfile.ZipFile(wr_zip)
extract(zipfd, wr_csv, wr_csv)

The reason this fixes it is because at the moment (Python 2.6/2.7 I believe) the zipfile.ZipFile class has no __exit__ attribute, so it does not work with a `with statement` as other file objects do.

Remove specific HTML tags using PHP

Thu, 21 Mar 2013 16:28:44 +0000

There are times when you want to remove a specific HTML tag from an HTML block of text.

This could be an anchor(<a/>) or an image(<img/>) perhaps.

You can use preg_replace to do this quite quickly and efficiently.

Remove an anchor:

$content = "Sample text <a href="#">Our anchor</a>. Etc etc";
$content = preg_replace('/<\/?a[^>]*>/','',$content);
//$content is now -> "Sample text. Etc etc";

Remove an image:

Keep Google Map v3 centered when browser is resized

Fri, 08 Mar 2013 00:05:21 +0000

Using Google Maps V3 Javascript API you can keep the map centered to the browser’s window by using the following trick when resizing the window.

var mapOptions = {
zoom: 2,
center: new google.maps.LatLng(0,0), mapTypeId: google.maps.MapTypeId.ROADMAP
};

var map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);

// this is our gem
google.maps.event.addDomListener(window, "resize", function() {
var center = map.getCenter();
google.maps.event.trigger(map, "resize");
map.setCenter(center);
});

Buy a Google Nexus 10 in the UK!

Sat, 29 Dec 2012 21:43:26 +0000

If you are looking to get a Google Nexus 10 inch tablet and are based in the UK you are in for a shocker!

The only place to buy it is at the Google Play store and since about the middle of November 2012 they have been sold out.
Some people say it’s due to delayed deliveries and orders and some say it’s just bad management on Google’s behalf. I think the latter is probably the thing that actually happened as no other tablet providers seem to ever have this problem.

Let Joomla and MySQL interact!

Fri, 21 Dec 2012 15:32:47 +0000

I often need a quick and easy few lines to retrieve some data from MySQL using Joomla without all the MVC nonsense that usually goes about this topic.

So here is how I do it!

$dbSEL = JFactory::getDbo();
$dbSEL->setQuery("SELECT MAX(`start_price`) FROM #__some_table");
$dbSEL->query();
echo $dbSEL->fetchRow();

As you can see above, we get the current database object and then run a query on it.
You may notice the hash (#) in the SQL statement of this example, Joomla replaces that (as well as the underscores (__) with the database prefix which is configured, so on shared nodes you don’t have to type all that extra stuff that will need to be changed later.

Perform a Mysql Query using Joomla!

Fri, 23 Nov 2012 00:41:58 +0000

This is really actually meant for future reference for myself as lately I’ve been doing quite a lot of Joomla! mysql coding and have used the following code just short of 3million times.

$db = JFactory::getDbo();
$querySelectId = "SELECT `id` FROM #__some_table WHERE `user_id`='$user_id'";
$db->setQuery($querySelectId);
$db->query();
$data = $db->loadAssoc();

What we do in the above code snippet is select a user_id from some_table (#__) is short for whatever your database table’s prefix is (Joomla! replaces this itself) and then we perform the query and return the row’s `id` into the $data variable.

Refresh User Data in Joomla

Sun, 21 Oct 2012 15:51:15 +0000

I was busy with a custom component in Joomla, and it stored it’s own user_details based off of the main users table, but if the details were changed then I needed the system to update the session to reflect the changes.

This is what I did:

$user = JFactory::getUser();
$session = JFactory::getSession();
$session->set("user", new JUser($user->id));
$user = JFactory::getUser();

Extract email addresses from a string – PHP

Tue, 09 Oct 2012 09:17:56 +0000

Sometimes you need to extract multiple email addresses from a string and the following function will make all your dreams come true.

function extract_emails_from($string){
    preg_match_all("/[\._a-zA-Z0-9-]+@[\._a-zA-Z0-9-]+/i", $string, $matches);
    return $matches[0];
}

..and this is how you use it:

$text = "this is some text and here is an email address xxx@example.com, here's another xxx2@example.com, etc..";
$emails = extract_emails_from($text);

Now let’s use the data:

// as string
print(implode("\n", $emails));

// loop as array
foreach($emails as $email) {
    echo $email .",";
}

How to drive traffic to your website!

Fri, 28 Sep 2012 13:44:25 +0000

This is a very hot topic indeed.

Definitely one that everyone with a website should know all about.

To begin our journey we will look directly at the Traffic Generator Sites out there who – to be honest – are complete scams because all they really do is one of two things…

1.) Load your site into those annoying pop-under ad windows that users close immediately as they appear(not having opened them themselves)

jQuery limit fields to alphanumeric characters only

Wed, 26 Sep 2012 17:23:46 +0000

I was trying to restrict a form’s field from only allowing the user to enter alphanumeric characters into it. I looked all around and couldn’t find a nice way to do it without a plugin, so I wrote my own bind function that you can attach straight to an element.

$("#yourFieldsElementId").bind("keypress", function (event) {
	if (event.charCode!=0) {
		var regex = new RegExp("^[a-zA-Z0-9]+$");
		var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
		if (!regex.test(key)) {
			event.preventDefault();
			return false;
		}
	}
});

If you would like to restrict the input to only be numeric then do this:

Make a dynamic year dropdown using PHP

Tue, 18 Sep 2012 22:06:29 +0000

Ever wanted to have a dropdown that automatically showed the current year and the few years before it?

This is a quick and easy way to do exactly that!

<select name="year">
    <?php
    for($i=date("Y")-5;$i<=date("Y");$i++) {
        $sel = ($i == date('Y')) ? 'selected' : '';
        echo "<option value=".$i." ".$sel."-->".date("Y", mktime(0,0,0,0,1,$i))."";
    }
    ?>
</select>

Pad a string with zeros using PHP

Mon, 17 Sep 2012 14:07:33 +0000

Recently I had to create a code/username maker to fit into a certain type of pattern so that all “broker codes” (as they were called) followed the same path.
An example one looked like so:

HJTH0001

The number needed to increment and I wanted to use the auto-increment feature in the mysql database table that was driving this data to make it.

This was easy but I ended up with a code that looked like this:

ImportError: No module named MySQLdb (Python)

Mon, 23 Jul 2012 11:47:13 +0000

Trying to use MySQL with Python and getting an ImportError?

This is likely because you have not installed it to the system. You can do this on Ubuntu Linux by running the following code:

Also, remember that there is no MySQLdb for python3.x and above. There is however, a fork of it on GitHub at: https://github.com/PyMySQL/mysqlclient-python

Search for “arabic” is url request and change codepage – ASP

Thu, 12 Jul 2012 07:40:42 +0000

If you are using Classic ASP (yuck) to create an arabic section of a website you can search for the arabic string in your Request URI and then change the session’s codepage as follows:

if instr(1, request.ServerVariables("PATH_INFO"), "arabic") then
	session.codepage = 1252
end if

Windows 7 is better than Ubuntu 12.04 on desktop!

Thu, 28 Jun 2012 16:01:53 +0000

Today we have finalised for ourselves that Windows 7 is definitely a “better” operating system than Ubuntu 12.04 when it comes to desktop environments.

Now, I say “better” in quotes because the word is quite hard to use as is and “convince” everybody while doing so.

We started our journey on Windows 7 and after desperately needing a reinstall we decided to go for the latest version (at the time) of Ubuntu, which happened to be the brand spanking new Ubuntu 12.04.

Function split() is deprecated in PHP

Tue, 12 Jun 2012 16:57:11 +0000

You heard it right! split() is officially a deprecated function. That means that you can still use it if you are really brave and it will work correctly, but don’t expect to see it in later versions of PHP when they come out. Somewhere along the line it WILL not work at all.

It has been marked as “deprecated” due to the fact that the explode() function has the exact same output!

Disable Cache in jQuery

Thu, 24 May 2012 16:32:32 +0000

I usually run into this problem when dealing with good ol’ Internet Explorer (..any version of IE actually).

The problem is that IE tries to be smart and not tell you the new output of a file it fetches more than one time with the same filename, instead it shows you what it saw the first time it loaded that file.

You can imagine this would be insanely dumb if you were using a realtime application data source where a script output a different resultset each time, e.g. most database ajax requests.

Where is Technology heading, perhaps we should focus more on Software?

Mon, 21 May 2012 13:32:26 +0000

I often wonder to myself where the technology industry is heading as I see new things come out almost daily.

You look around and something you just bought is all of a sudden outdated. This can be quite irritating for the techno-geeks out there that always want the latest release of every gadget, as it makes it somewhat impossible to keep up with what’s in stores.

The really nice thing about software over hardware is that one can just perform a localised update instead of having to purchase new hardware everytime something changes or is improved. This all lead me to believe that perhaps things would be better if we could somehow come up with a device that is so well thought out with such good hardware that one could just perform regular software updates every once in a while and you would essentially have the “latest gadget around”.

How to break out of an iframe

Wed, 09 May 2012 13:53:25 +0000

So someone’s trying to make their site better by opening a page on your site inside of their site using an iframe?

They’re doing something like this:

<iframe src="http://www.example.com/your_page.html" width="100%" height="100%"></iframe>

Well how about you stop that from happening by pasting the following line in your website’s header!

<script type="text/javascript">
if (top.location != self.location) {
  top.location = self.location.href;
}
</script>

The above code basically does a check to see if the site is the same as what is said in the address bar, if not then it sets the parent’s frame (the other site) to change to your site’s location!

Edit hosts file on Windows 7

Wed, 09 May 2012 11:34:53 +0000

The hosts file is used to manually alter the hostname or IP address in place of it being served by a Nameserver, also known as via DNS.

The hosts file is located here:

C:\windows\system32\drivers\etc\

Or an easiler way to get to it incase of whatever is like this:

%systemroot%\system32\drivers\etc\

This file cannot be editted by “normal users” and requires all changes to be done via an Administrator.

This is really easy if you do it in the following way:

(EAI 2)Name or service not known: Could not resolve host name *.80 — ignoring!

Tue, 08 May 2012 15:14:10 +0000

You are no doubt trying to add a vhost and you get the following error when attempting to affect changes by restarting the http daemon (httpd):

(EAI 2)Name or service not known: Could not resolve host name *.80 — ignoring!

Not to worry!

Add the following text to httpd.conf at the bottom (That’s at /etc/httpd/conf/httpd.conf):

NameVirtualHost 12.34.56.78:80

ServerAdmin yourename@yourserver.com
DocumentRoot /var/www/html/the_path/
ServerName the_path.example.com
ErrorLog /logs/the_path.example.com-error_log
CustomLog /logs/the_path.example.com-access_log common

Now just restart the http daemon:

Virgin Media blocks torrent sites!

Thu, 03 May 2012 12:08:42 +0000

Virgin Media have done it again! They have gone and started a “downloaders war”, I’m sure of it.

Basically what happened is that Virgin Media are claiming that they have had an order from the Courts to prevent access to a whole bunch of sites which lead to illegal downloading or copyright infringement downloading.

Not only is it Virgin Media but all 5 major ISP’s in the UK that have received this Court order, that’s Sky, Everything Everywhere, TalkTalk, O2 and Virgin Media. The initial case was against the Swedish file-sharing website The Piratebay. The Court order sets in as of the 1st of May 2012 and originated in July 2011 when The British Phonographic Industry asked The Piratebay to remove selected torrents and The Piratebay refused, so they took them to court in December. In February Justice Arnold ruled that the The Piratebay incite their users to commit copyright infringement.

How to Comment out a line in a Crontab on Linux

Thu, 03 May 2012 10:31:53 +0000

Firstly let’s just note that crontabs are read in the following way:

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)

Your current crontabs can be viewed on your linux setup by typing in the following command:

DateTime conversion function using PHP

Tue, 01 May 2012 16:10:26 +0000

It’s really very simple to convert times in different timezones using the following function.

function dateTimeConversion($datetime, 
$timezone="Europe/London") {
  $date = new DateTime($datetime, new DateTimeZone("UTC"));
  $date->setTimezone($timezone);
  return $date->format("Y-m-d H:i:s");
}

As you can see, it takes 2 arguments, $datetime which is a time string and a $timezone which is a timezone to convert to.

A usage example would be:

echo dateTimeConversion("2012-05-01 17:09:58");

Convert seconds to days, hours, minutes, seconds in PHP

Tue, 01 May 2012 12:54:37 +0000

With the following function you can easily convert an integer containing seconds to a nice days, hours, minutes, seconds string or array.

function secondsToTime($seconds, $return_type="string") {
// extract days
$days = floor($seconds / 3600 / 24);

// extract hours
$hours = floor($seconds / 3600) - $days*24;

// extract minutes
$divisor_for_minutes = $seconds % 3600;
$minutes = floor($divisor_for_minutes / 60);

// extract the remaining seconds
$divisor_for_seconds = $divisor_for_minutes % 60;
$seconds = ceil($divisor_for_seconds);

// return the final array
$obj = array(
"d" => (int) $days,
"h" => (int) $hours,
"m" => (int) $minutes,
"s" => (int) $seconds
);

$str = "";
if ($obj["d"]!=0) $str .= $obj["d"]."d ";
$str .= $obj["h"]."h ";
$str .= $obj["m"]."m ";

if ($return_type=="string") return $obj["d"]." days, ".$obj["m"]." minutes, ".$obj["h"]." hours, ".$obj["s"]." seconds";
else return $obj;
}

To use the above function you can either use the default return type and call it like so:

Remove dotted outline around anchors

Mon, 30 Apr 2012 08:16:41 +0000

This has become quite a common question asked by many website owners.

“How do I remove that dotted outline around an anchor?”

Lucky for you all, it’s a really easy one to resolve as well. You just have to take a look at CSS for a second and add one line as follows:

a { outline:0; }

This will disable the outlines around clicked links all around your site.

Now that you know how to do it you may want to read about why you shouldn’t do this!
Click here to read the petition to not do this.

Get amount of hours between 2 hours

Fri, 27 Apr 2012 14:02:21 +0000

If you would like to get the amount of hours between 10:00 and 12:00 then use this!

function timeDiff($firstTime,$lastTime) {
  $firstTime=strtotime($firstTime);
  $lastTime=strtotime($lastTime);
  $timeDiff=$lastTime-$firstTime;
  return $timeDiff;
}

echo (timeDiff("10:00","12:00")/60)/60;

How to embed HTML5 video with fallback

Fri, 27 Apr 2012 10:33:28 +0000

A common question with the rise of HTML5 becoming more and more common and the whole iGeneration (iPhones/iPads/iEtc) is “how can I embed a video on my site without using a flash player?”. If you’re working with HTML, you might also be interested in how to correctly form HTML and how to place HTML div on top of Flash.

An option that really does work quite well is to use the JWPlayer and set it up to use HTML5.

How to backup all mysql databases

Thu, 26 Apr 2012 11:08:59 +0000

In order to backup all mysql databases, you can run the following command in your linux command line:

The example below is configured with username “theuser” and password “thepass”.

mysqldump -utheuser -pthepass ?all-databases > all_dbs.sql

Invalid command 'RewriteEngine'

Thu, 26 Apr 2012 11:06:02 +0000

If you receive the following error message if means that mod_rewrite is not enabled in Apache:

Invalid command ‘RewriteEngine’, perhaps misspelled or defined by a module not included in the server configuration.

a2enmod rewrite

Bear in mind this is done like this on Linux Ubuntu, not entirely sure if this works for other flavours too.

How to get the Hours Difference (in HH:MM format) in PHP

Thu, 12 Apr 2012 12:08:10 +0000

It’s very simple to get the difference in hours using PHP

function timeDiff($firstTime,$lastTime) {
    $firstTime=strtotime($firstTime);
    $lastTime=strtotime($lastTime);
    $timeDiff=$lastTime-$firstTime;
    return $timeDiff;
}

echo (timeDiff("10:00","12:00")/60)/60;

Warning: Invalid argument supplied for foreach()

Tue, 28 Feb 2012 11:04:22 +0000

A common error which occurs with foreach loops is the standard “Invalid argument supplied for foreach()” whch gets thrown up as a warning.

This can easily be overcome by wrapping the foreach loop in a conditional if statement which checks to see if the argument supplied to the loop is an array or not.

Below is an example of how to correct the problem:

if (in_array($arrItem)) {
  foreach($arrItem as $arrItemi) {
    // use $arrItemi;
  }
}

Unable to connect to any of the specified MySQL hosts.

Sun, 19 Feb 2012 14:59:04 +0000

If you get the following error while trying to connect to a MySQL database using a third party client such as TOAD or SQL Workbench, then you need to edit your mysql server’s my.cnf file.

Error Message: Unable to connect to any of the specified MySQL hosts.

PHP nl2br on one line

Sat, 18 Feb 2012 15:35:10 +0000

I usually store data from a textarea directly to the database as is, then once I retrieve it back into HTML I use that lovely PHP function nl2br() to convert it to HTML
tags.

This works well for most cases until you are passing this data back into javascript where everything has to be on one line!

nl2br() outputs as follows:

Line one
Line two

And I want it to be as follows:

LEN in MySQL

Wed, 01 Feb 2012 12:10:18 +0000

In MySQL 5.1 LEN is called LENGTH, you use it exactly the same and pass in the link, so: LENGTH(link).

Remove all linebreaks in PHP

Mon, 30 Jan 2012 09:22:57 +0000

If you are having problems with a string that keeps adding a line break when output from PHP to HTML then the following code will work wonders for you!

$string_with_line_break = "blabla\nbla\r";
$string_without_line_break = trim(preg_replace( "/\s+/","",$string_with_line_break));

IE9 adding empty table cells in large table

Tue, 24 Jan 2012 11:37:14 +0000

Well as usual, we are once again fighting the woes of the beloved Internet Explorer, and it appears that Microsoft’s latest greatest new and improved browser rival to the market IE9 still has a whole bunch of irritations and retardation to worry about (saw that one coming).

Today I was busy loading a massive amount of data into the body of a table using ajax and in Firefox and even Internet Explorer 8 it worked quite well, but Internet Explorer 9 decided that it would like to add some empty table cells randomly around my “massive table”, now of course I began by kicking something and cried a few times….. but then I thought about whitespacing and the usual problems I had found with it before while using “the best browser ever known to human-kind”(…not) and I thought of removing the whitespaces between the ’s and ’s.

SELECT Duplicate Items Using SQL

Tue, 20 Dec 2011 15:52:04 +0000

If you have a table which has duplicate items in then you can use the below statement to select them.

SELECT * FROM tableName
GROUP BY columnName
HAVING ( COUNT( columnName) >1 )

MySQL Error: Can’t get hostname for your address

Wed, 14 Dec 2011 15:15:41 +0000

This error is thrown by MySQL because it tries to do a DNS lookup on the address connecting to the server and it fails due to the IP not being able to be resolved back to a name or some-other deeper DNS bust problem.

The easiest way to fix this is to edit your my.ini or my.cnf (/etc/my.cnf) and in the
[mysqld] section add the “skip-name-resolve” option.

Near the top of the file this will look similar to the below:

Adobe drops flash for mobiles!

Wed, 09 Nov 2011 17:54:54 +0000

..and it’s official – so says Adobe’s blog (read it here). Adobe will be dropping support for Flash on future devices due to performance and a few other things, pushing the future more towards the HTML5 route, which isn’t neccessarily a bad thing, I just find it quite ironic and somewhat comical that they waited for Steve Jobs (Apple) to die before giving up their long time fight with Apple about Flash being or not being supported on mobile devices, namely the iPhone.

jQuery Colorbox not showing but background shows

Tue, 08 Nov 2011 11:30:06 +0000

I was using Colorbox for some lightbox type effects to show larger images when clicking on thumbnails, but for some reason the background was showing up but the pretty little box in the middle where the larger image is supposed to show never showed up, so this is how I made it finally appear after many failed attempts!

$("document").ready(function(){
$(".theCssClass a[rel='forGroupingRelCodeGoesHere']").colorbox({ onLoad: function () { $("#colorbox").show(); } });
});

So the “real” code that fixed it was the:

Get Value of Checkbox using jQuery

Tue, 25 Oct 2011 08:49:11 +0000

This one is quite an easy one, but a good one to mention non-the-less as it does definitely come in really handy.

If you would like to get a checkbox’s value to send to the backend using jQuery you can always do the following:

Firstly let’s draw some HTML to illustrate our example.

<input id="chkOurCheckbox" type="checkbox" />

Now we need some jQuery to do the real work.

var ourCheckboxValue = ($("#chkOurCheckbox:checked").val()=="undefined") ? 0 : 1

In our above example we draw an HTML checkbox to the screen and then use jQuery to return the value of it.

Everybody’s a web host

Wed, 28 Sep 2011 09:39:00 +0000

To cut straight to the point, “we’re living in the age where everybody’s a web host”. Whether it be small and quite pathetic or just another reseller of a larger service trying to get their cut of things, everybody truly is spamming the world with more and more web hosting packages.

Just a few short years ago this problem didn’t exist and getting web hosting was quite expensive, unless you went with free services such as the good ol’ “geocities” and co, but then larger companies started up their shared hosting and reseller hosting packages which immediately led to everybody thinking all it took to become a web host was to get themselves a reseller account and start trading. For the most part that isn’t so far off, as 95% of the websites out there sit mostly idle while almost nobody visits them and therefore it’s perfectly fine to share a single machine between multiple clients and call it “excellent web hosting”, but these small guys also try and compete with the larger players in the industry and end up creating quite a mess of things, all while flooding search engines and web development and hosting forums with “hosting deals and specials”.

CSS Background Default

Thu, 15 Sep 2011 17:10:46 +0000

If you would like to override an already attached class containing a background then you can use the following:

background:transparent none 0 repeat !important;

Restrict PHPMyAdmin to IP Address

Mon, 22 Aug 2011 18:27:21 +0000

Would you like to restrict PHPMyAdmin from being accessible to the whole world?

Firstly you need to SSH into your box if you are not on the local machine where PHPMyAdmin is installed along with Apache.

cd /etc/phpmyadmin/
vi apache.conf

You will need to look for the following text “<Directory /usr/share/phpmyadmin>” and add in the below code:

Remember that you need to press “i” in order to start editting text if using VI.

2014 – Commands out of sync; you can’t run this command now

Thu, 04 Aug 2011 14:06:02 +0000

#2014 – Commands out of sync; you can’t run this command now

Now that can be a really annoying error!

It happens when querying stored procedures in phpMyAdmin as mysqli seems to return 2 sets of results opposed to the usual 1 that mysql returns.

You cannot call anything else until you have “flushed” or “cleared” the second result.

You can try using COMMIT to resolve this.

Image corrupt or truncated: “unknown”

Wed, 13 Jul 2011 15:09:27 +0000

What is “Image corrupt or truncated: ” and what does it mean?

This can often be seen while using Firebug in Firefox, but it actually has nothing to do with either and is just the error being reprinted in in firebug in most cases.

It comes from an image that has had it’s extension changed from say .gif to .png or .png to .ico. Eventhough .png and .ico file types are very similar, they are not the same, so an error occurs.

WordPress wp-admin use different language for user

Thu, 07 Jul 2011 11:59:55 +0000

I needed to do some work on a WordPress site a little while ago and all the admins were French – and I cannot speak French other than the popular swear words – so had no idea what was going on in the /wp-admin/ so needed some way of enabling my newly created user account to be in english while letting everybody else use french as they had been up til that point.

Replace all spaces in HTML with except in HTML tags using PHP

Sun, 29 May 2011 17:56:13 +0000

If you would like to replace all the spaces in an HTML string with so that you can render it out to the browser but you also want to retain current spaces in HTML tags you can use the below method:

$inputString = '<span class="color:red">1</span> 2 3';
$outputString = preg_replace_callback("#>[^<]+<#","relSpaces",$inputString);

function relSpaces($match){return str_replace(" ","'",$match[0]);}

This will replace:
1 2        3

..to look like this:

Using PHP to validate an IP address

Wed, 18 May 2011 09:47:13 +0000

You can use the PHP code below to check if an IP address is valid or not.

$ip = ""; //enter a valid or invalid ip address here
if(filter_var($ip, FILTER_VALIDATE_IP)) {
  // The IP Address is valid
} else {
  // The IP Address is not valid
}

Wasn’t that easy!?!

What is the difference between is_home() and is_front_page()

Fri, 13 May 2011 19:47:49 +0000

Call me ignorant, or call me an ignorant geek, but I used to think is_home() and is_front_page() was the same thing, until I experimented with them the other day and noticed they did quite different things. Let me break them down:

is_home()

This actually is the page where all your recent posts are shown. Which means if your “home” page is set to “static” then it will be false, otherwise it will be true.

..near 'option o ON (po.option_id = o.option_id) LEFT JOIN option_description od ON (o.o' at line 1

Mon, 09 May 2011 15:59:02 +0000

So you’ve just installed Opencart 1.5.0 and when attempting to edit a product or category or etc you get the following error:

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘option o ON (po.option_id = o.option_id) LEFT JOIN option_description od ON (o.o’ at line 1
Error No: 1064
SELECT * FROM product_option po LEFT JOIN option o ON (po.option_id = o.option_id) LEFT JOIN option_description od ON (o.option_id = od.option_id) WHERE po.product_id = ‘42’ AND od.language_id = ‘1’

What is 1e100.net?

Thu, 05 May 2011 14:33:20 +0000

So you are probably reading this because you are not sure what 1e100.net is or why you are being redirected via it when performing Google searches or using products such as youtube etc.

Perform a SiteWhois lookup

1e100.net is owned by Google and has been in use since October 2009, if you perform a whois on the domain you can see it’s registration details linked back to Google.

Perform an SiteInfo lookup

Hide all error messages PHP

Thu, 28 Apr 2011 10:03:20 +0000

PHP Error messages showing up in your web applications are a dangerous thing. Not only does it look unprofessional, but it is also a serious security concern!

Once you have completed debugging your website or web application you can place the following one liner at the beginning of your code, this will turn off error reporting and therefore make sure that no application details are spilled to your users.

error_reporting(0);

If a single line of code is causing the problems it is safer to use the at symbol (@) to suppress any errors it may cause.
You can also use “or die()” to stop the execution of your code after the suppressed error in case the remainder of your code relies on that function to return a value.
In the example below we will use the “@” and “or die” to handle everything:

What is xmlrpc.php?

Tue, 22 Feb 2011 12:02:59 +0000

It is a script which allows clients to make procedural calls over the net.
As it says in the name, the encoding is XML and because it is used on websites we can make the fair assessment that it uses the HTTP protocol.

If we break the name down we get: XML transmition via Remote Procedure Calls.

So you are still not sure what this is all about? Read on..

Windows Genuine Advantage Notifications in a VM

Fri, 11 Feb 2011 14:14:51 +0000

Windows Genuine Advantage Notifications

I am running a Windows XP SP3 VM used for testing multiple versions of InternetExplorer through Virtualbox.

Running this wizard should be avoided if Windows is in a VirtualMachine.

Force HTTP using htaccess

Sat, 04 Dec 2010 23:23:33 +0000

RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://www.example.com/$1 [R,L]

Stop That Referrer in PHP!

Mon, 01 Nov 2010 13:34:50 +0000

Today I will show you a method to stop the traffic that a referrer site is sending your way, you may wonder why you would want to ignore traffic, after all, isn’t inbound traffic to your site fantastic no matter what?

The simple answer is “NO!”

Let me explain it in a real life situation so that you can better understand where to use this.

Understanding where to use it

Viva la 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0!

Tue, 26 Oct 2010 09:49:38 +0000

You may see this around and not have a clue what the heck it is, weirdly enough, I did..
Why “weirdly” you ask, well, because, who would be looking for something like “09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0”.
Let me elaborate..

The Urban Dictionary says it like this:
“An alphanumeric string denoting a hack and insecurites in the HD-DVD coding.”

Ternary Operation

Tue, 12 Oct 2010 11:46:56 +0000

If you do not know what the Ternary operator is, or do not use it while you are coding, let me be the first to tell you how much you are missing out!

The Ternary operator looks like this: “?”, that’s right, it’s a question mark!

My favourite way of using it is to shorten Conditional If Statements, so let me show you what I’m on about.

Oops the system encountered a problem (#104)

Mon, 11 Oct 2010 19:10:22 +0000

If you get the following error while using Google’s Gmail Service (gmail.com):

Oops? the system encountered a problem (#104)

..then you should try deleting your browser’s cache and everything will be resolved.

This appears to be a local problem and not on the Google servers as data is pushed via cookies to the local machine using the web service.

How to Write Unmaintainable Code

Wed, 22 Sep 2010 14:56:09 +0000

I have come across the following article before and again came across it today, after a revised browse through, I thought I may as well add another link to it on the web for whoever ends up clicking on it!

It really is a worthwhile (in a humor sort of way) read:

http://www.freevbcode.com/ShowCode.Asp?ID=2547

Captcha Fail!

Thu, 16 Sep 2010 15:34:56 +0000

Hey, thought I’d just post this one incase anybody else sees it and thinks it’s funny.

This is not really a very helpful post like most of the others on this site, but HEY! TOUGH!

So feel free to smile if you like..

What do you know, a snippet of helpful-ness is about to appear-> This issue is usually caused by an invalid referrer! HA!

Test IE versions on any machine!

Thu, 16 Sep 2010 11:20:21 +0000

Do you do web development and are unable to test your software in old shitty versions of Internet Explorer?
If so then you may want to read on a little bit.

Microsoft has got a whole bunch of virtual images you can download for FREE(not a usual Microsoft word) over here:

http://www.microsoft.com/downloads/en/details.aspx?FamilyId=21EABB90-958F-4B64-B5F1-73D0A413C8EF&displaylang=en

They contain an operating system and an install of your favourite IE version! Hooray!

Error 500 php_value .htaccess

Tue, 14 Sep 2010 13:00:23 +0000

I noticed on some server setups I could not do the following inside a .htacess file:

 php_value upload_max_filesize 250M php_value post_max_size 250M 

I was getting an error 500 Internal Server Error with the above code in the .htaccess file.

What to do to correct this is create a file called php.ini and save it in the same location as your .htaccess file and enter the following code instead:

 upload_max_filesize = "250M" post_max_size = "250M" 

Windows Directory Tree Never Finishes Loading?

Tue, 14 Sep 2010 11:06:03 +0000

I am running Windows 7 64-bit and since yesterday whenever I open “My Computer”/“Windows Explorer” (-Windows+E) the initial “showing drives” screen is frozen, so I have to use the address bar to navigate to the path I need to go.

As you can see in the picture to the left even after you have gotten to and are viewing the folder you want, the directory tree in the sidebar continues to “check” for “who knows what”!

CSS background image data: base64?

Thu, 09 Sep 2010 16:22:53 +0000

What the heck is all that Gobbledygook in the CSS?

So you have noticed that bit of css that says something like this in the CSS source-code and you have no idea what it could be?
url(“data:image/gif;base64,R0lGODlfMAMEAIABAKysrObm5iH5BAEAAAEALAAAAAAwAwQAAAJOhI+py30Bo5y02ouz3rz7D4biSJbmiabqyrbuC8fyTKPOjedHzff+DwwKh8Si8YhMKku6pvOxjEqn1Kr1is1qt7ynV8cNi8fksvmMTiMLAD4=”) no-repeat scroll 50% 0 transparent

It is a technique called Data URLs and using PHP – or your favourite server-side script – you can generate these nifty little things.

WordPress remove Subscribe to my RSS feed after posts

Wed, 08 Sep 2010 23:37:41 +0000

If you are running WordPress and have noticed a line under all your posts that says:

If you enjoyed this post, make sure you subscribe to my RSS feed!

..and if this irritates you as much as it did me, you can remove it by deactivating a plugin called Subscribe Remind.

Done!

P.S. Sorry Trevor, not trying to piss you off 😛

And then there was Google Instant!

Wed, 08 Sep 2010 23:00:14 +0000

If you have visited the Google.co.uk homepage (Yes, that’s Google UK) recently – since about the 8th of September 2010 then you would have noticed a new search feature Google is pushing called Google Instant.

Now what is so nice about Google Instant?

It is an ajax type search application that now searches using keyword ghosting and searches and returns results as you type to populate the normal search results page that has been used up until now.

[Solved] PHP’s typeof – gettype()

Mon, 06 Sep 2010 08:47:30 +0000

Quite often you may need the ability to check what type of data type a variable is.

In most programming languages this is possible to do and is usually called something like typeof().

So what is typeof in php, or typeof php you ask? In PHP there is a simple function called gettype() and it’s so easy to use.

All you have to do is pass the variable in question to gettype() as the first argument and the type will be returned.

When to use SSL?

Fri, 03 Sep 2010 14:23:01 +0000

There has always been quite a lot of heated discussion around the question of when to use SSL and when to avoid it while building websites.

I have been asked this question a few times myself and finally thought that it would be good for everybody if I just wrote an article on it explaining what the big huff was all about.
Obviously if anyone has anything to add or if you disagree with me for whatever reason, then feel free to do so below at the end of this article.

IE6 PngFix in Javascript

Thu, 02 Sep 2010 11:36:02 +0000

As a web developer you will know just how much we all love hate Internet Explorer 6 – one of the most dreaded browsers and browser versions that still exists in the deep dark corners of the interwebs – and you will probably have figured out that it doesn’t play well with PNG images.

MSSQL Select Not Null

Thu, 02 Sep 2010 10:46:59 +0000

I mainly use MySQL these days, so get screwed over for a few minutes when I have to do something in MSSQL that is slightly different when it comes to it’s custom syntax.

If you want to show all entries in a specific column and where it is not Null then you can do the following:

SELECT [columnNameHere]
FROM [databaseNameHere].[dbo].[databaseTableNameHere]
WHERE [columnNameHere] IS NOT NULL

What is utma, utmb, utmc, utmz ?

Wed, 01 Sep 2010 17:29:58 +0000

__utma, __utmb, __utmc and __utmz are 4 cookies created by Google Analytics, for a detailed and very informative read, go here and here.

How to Close Bandmix Account

Tue, 31 Aug 2010 08:12:37 +0000

If you want to close a Bandmix account, then:

Login to bandmix.co.uk
Go to Options – http://www.bandmix.co.uk/account/options/
Click Decline Service
Then click the button called Decline Service at the bottom.
Click “OK” to the verification popup.

Account closed!

Google Redirect Virus Fix!

Fri, 27 Aug 2010 13:23:26 +0000

Now this is an annoying one.
You go to any of google’s sites including any site that has google-analytics.com javascript included in it’s body and BOOM! ..either you get redirected to a bullshit search page you didn’t ask to go to or the browser shows a blank white screen while apparently analytics loads..

It turns out this is actually a virus that infects routers!

Chromium Operating System

Mon, 23 Aug 2010 16:46:37 +0000

As many of you may know, Chromium is an opensource project that is basically an Operating System built on Linux and is just like working in Google’s Chrome web browser.

I decided to take a look at it today and went and downloaded the developer sneak release.

It came all boxed up in a 764,994KB (764MB) VMDK Virtual Machine Harddisk file.
When it finished downloading I was sadly quite excited as I love trying out new Operating Systems and goodies – being a geeky kind of guy like most guys out there – and after hardly any setup at all it started up.

Super Easy Email Validation AS2

Fri, 20 Aug 2010 10:45:21 +0000

I needed a quick and easy way to check for the basics of an email address.

Does it contain “@” and “.” symbols.

This is by no meals a foolproof method, so don’t use it for anything big, but if you want to just do a quick test then here you go:

var email:String = "name@server.com";

if (email.indexOf("@")!=-1 &amp;&amp; email.indexOf(".")!=-1) trace("false");
else trace ("true");

VLC Cache Rant

Tue, 17 Aug 2010 11:51:07 +0000

The first time this ran it took for freakin’ ages!

This should take less than a few minutes

What the hell is that supposed to mean? Less than a few? 73 minutes perhaps?

Rant over..

ODBC SQL Server Memory General Network Error

Mon, 09 Aug 2010 12:15:38 +0000

Microsoft OLE DB Provider for ODBC Drivers error ‘80004005’[Microsoft][ODBC SQL Server Driver][Shared Memory]General network error. Check your network documentation./site/path/to/script/aspfile.asp, line #

..and that’s what it throws you!

At about this point you may want to scream, or just be a tad annoyed by that damn machine running your site.
Basically your server is either one of two things, and those are:

XML cannot be the whole program

Mon, 26 Jul 2010 10:09:03 +0000

What the hell does that mean?

You can get this error thrown up in your good old trusty Firebug console.
It expects a script to be returned as an ajax type datatype.

So all you have to do is change your datatype to output as XML.

Mocha Java Decompiler Download

Fri, 25 Jun 2010 15:07:04 +0000

Mocha is a Java Decompiler and is 100% FREE to use.

The readme.txt file in the Mocha distribution offers the free usage license:
The distribution archive (file “mocha-b1.zip”) may be distributed freely, provided its contents (“mocha.zip” and this file, “readme.txt”) are not tampered with in any way.

I am pleased to be able to make the Mocha distribution available under those terms:

mocha-b1.zip (121K)

You can visit the alternative download location here.

EAI_NODATA

Thu, 24 Jun 2010 13:12:29 +0000

Error message: Connection attempt failed with “EAI_NODATA – No address associated with nodename”.

The above error occured while using Filezilla (Ftp Client), it either means that you do not have an active internet connection, OR it means that you need to clear the private data because the connection to the server was lost while an active FTP connection was still present. Upon reconnection to the server (which is sometimes automatic) you will receive the EAI_NODATA error.

1180 Call to a possibly undefined method navigateToURL

Fri, 18 Jun 2010 10:50:58 +0000

1180 Call to a possibly undefined method navigateToURL

If you get the above error when trying to run your flash actionscript 3 file, you are obviously trying to use the navigateToURL() function but have not imported the flash.net library code.

The following code before everything will correct the problem.

import flash.net.*;

..or a more of a direct unbloated method is as follows:

import flash.net.navigateToURL;

Test Your Password Strength

Thu, 10 Jun 2010 13:46:59 +0000

I came across this site today and it’s quite an interesting one as it works out the approximate time it would take a desktop pc to crack the password.

Check it out here.

How to use a Timer in Actionscript 3

Thu, 10 Jun 2010 10:16:47 +0000

It is really easy to create a Timer in Actionscript 3.

Instantiate the Timer Class and pass a time in millions of 1000 to it to work in seconds.

var myTimer:Timer = new Timer(1000);

Setup an event listener to call a function.

myTimer.addEventListener("timer", myTimerEventHandler);

Start the Timer.

myTimer.start();

Start the Timer.

function myTimerEventHandler(event:TimerEvent):void {
  trace(myTimer.currentCount+" seconds have passed.");
}

So altogether we have this.

var myTimer:Timer = new Timer(1000);
myTimer.addEventListener("timer", myTimerEventHandler);
myTimer.start();
function myTimerEventHandler(event:TimerEvent):void {
  trace(myTimer.currentCount+" seconds have passed.");
}

Now you know how to use a Timer in Actionscript 3.

Google Background Image

Wed, 09 Jun 2010 17:37:57 +0000

Google now allows you to add a background image to the google homepage to apparently make it more, like, home.. hmmmm

Just by clicking the button at the bottom left hand corner it allows you to either upload an image or select an image from google.

For indepth instructions as per Google, check this page out: http://www.google.com/support/websearch/bin/answer.py?answer=180720&hl=en

How to Hire a Hacker

Wed, 09 Jun 2010 14:00:06 +0000

I came across a very interesting and quite funny read, take a look here for How to Hire a Hacker: http://www.setec.org/hirehacker.html

If the program is already running, close it before attempting to run.

Tue, 08 Jun 2010 11:03:41 +0000

Launch Failed!

If the program is already running, close it before attempting to run.

I don’t know how many times I have gotten this error message while trying to Run a project in Adobe Flash Builder.

For all of you stuck with this message and unable to ever get your projects going, there is quite a simple fix to this.

All you need to do is open up Task Manager (Ctrl+Shift+Esc) and click on Processes, then “End Process” on any instances of “adl.exe” you find. Only one adl.exe instance can run at any given time.

Random Number In ASP for no Flash Caching

Fri, 04 Jun 2010 09:12:37 +0000

This is an example of how to create a random number in Classic ASP in order to append to a swf file so that the browser does not cache the swf file.

<% Dim SwfRndNum Randomize SwfRndNum = Rnd %>

You can then add it to your swf embed code as follow, bear in mind that I am only showing the snippet around the swf file name and not the entire embed code.

Why we don’t choose MSSQL!

Wed, 26 May 2010 12:45:36 +0000

Everybody always raves how great Microsoft SQL Server is, and how much data it can hold, and how much bigger it’s “package” is than your own.

But the truth is that I hate it with a passion!

I use RDBMS‘ on a daily basis and never used to hate MSSQL so much until recently when I had to modify a very large site that was built in Classic ASP(yuck) and MSSQL.

How Do You Fire A Client?

Thu, 20 May 2010 13:05:04 +0000

How do you fire a client?

Let’s face it, some clients can be a real nightmare.

There are a whole bunch of tell-tail signs that a client is going to be a major problem for you shortly after or sometimes during your first interaction with them. This can be a phone call, a few emails or worst of all, a face to face meeting.

Remember that you need to be selective when it comes to work you take on, as a bad client can cause more trouble than they’re worth. They can even bankrupt you if you’re not careful.

How to get ‘how many days in February’ using Javascript?

Wed, 19 May 2010 12:41:20 +0000

It is quite handy to have a function that can tell you how many days there are in February due to the leap year shift of either 28 or 29 days.
Below is a function created in Javascript to return the exact amount of days according to the year given:

function daysInFebruary (year){
    return (((year%4==0)&&((!(year%100==0))||(year%400==0)))?29:28);
}

Weird Pagination on a Google Page

Mon, 17 May 2010 13:32:55 +0000

Not sure how long this one will last, but for now:
Go to: http://www.google.co.za/search?q=MFI/06/ASA-778658&hl=en&start=0&sa=N

If you scroll to the bottom, there are 4 pages (pagination), press Next, now there are only 2, WEIRD HUH!

Actionscript 2 – PHP Data Transfer

Mon, 17 May 2010 12:09:32 +0000

In the below example we will use Actionscript 2 to call a remote PHP file that will return data to it.
It is a simple way of transferring data between the server and client.

Actionscript 2 Code:

callRemoteFile = function(ourVariable:String) {
var result_lv:LoadVars = new LoadVars();
result_lv.onLoad = function(success:Boolean) {
if (success) {
if (result_lv.message=="success")
trace("done! "+result_lv.returnValue);
else
trace(result_lv.message);
} else {
trace("Error connecting to server");
return false;
}
};
var send_lv:LoadVars = new LoadVars();
send_lv.ourVariable = ourVariable;
send_lv.sendAndLoad("/example/file.php", result_lv, "POST");
}
callRemoteFile("some text here");

PHP Code:

<?php
	if (isset($_POST)) echo "a=1&message=success&returnValue=".$_POST["ourVariable"]."&b=2";
	else echo "a=0&message=failed&returnValue=nothing&b=1";

Unique Random Numbers in PHP

Thu, 13 May 2010 13:55:15 +0000

If you would like to show random numbers using PHP you can do this:

<?php
	$min = 1;
	$max = 100;
	$total = 100;
	$arrItems = array();
	while ( count($arrItems) < $total ) {
		$item = mt_rand($min,$max);
		if (!in_array($item,$arrItems)) {
			$arrItems[] = $item;
			echo $item."<br />";
		}
	}

HTML mail() Sending as Plain Text

Tue, 11 May 2010 14:25:14 +0000

$to = "email@address.com";
$subject = "SUBJECT";
$message = "<b>MESSAGE</b>";
$headers = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
$headers .= 'From: Mailer ' . "\r\n";
mail($to, $subject, $message, $headers);

The above code does not always send emails in HTML as it should, it turns out there is a PHP Bug (http://bugs.php.net/15841) that comes into play with QMAIL and carriage returns.
If this is the case you should replace “\r\n” with a “\n” only.

Turbo C++ in DosBox for Windows 64bit

Fri, 07 May 2010 17:31:35 +0000

I had to compile a C++ application under a DOS environment and was running Windows 7 64bit.

Firstly, Turbo C++ is a 32 bit x86 application and therefore will not run when initialised from an x64 environment.

This can easily be solved by installing the DOS Emulator called DosBox. One can then mount the Turbo C++ folder as a drive and install it under a subdirectory.

e.g. mount c c:\PathToMyTurboCppDirectory\

Once in there it’s quite easy to open and compile the source code, but good luck to anyone that tries to write anything from scratch, it’s really painful and half the keys are not mapped in the DosBox, eventhough you can press Ctrl+F1 to open the Keymapper.

Case Insensitivity with .htaccess files

Wed, 05 May 2010 17:28:06 +0000

If you have an .htaccess file to control the flow of URI’s on your site you may want to look at adding a nice little “case insensitive” feature to each line/item.

So an example of a line of .htaccess without any case insensitive bells and whistles looks like this:

RewriteRule ^AndrewOdendaal$ index.php?go=2964

We add our Case Insensitive feature by just adding a [NC] to the end of the line, like this:

Actionscript2: Split string by line length with & without word-wrap

Wed, 05 May 2010 11:04:25 +0000

Split string into sentences by max line length.
This uses a character array but doesn’t use word-wrapping.

var personalMessage: String = "You got this far so we reckon that you could be curious enough to learn a little more, we?ll contact you shortly to answer any questions you may have.";
_root.myArray = new Array();
_root.myArray = personalMessage.split("");
_root.mySentences = new Array();
var currentCharCount: Number = 0;
var currentCharItem: Number = 0;
var currentCharString: String = "";
var maxLength: Number = 65;

for (var i = 0; i & lt; _root.myArray.length; i++) {
    if (currentCharCount & lt; maxlength) currentcharstring = "" += "_root.myArray[i];"
    if = ""(currentcharcount = "=maxLength" || = ""
        currentcharitem = "=(_root.myArray.length-1))" {
            = ""
            _root.mysentences.push(currentcharstring); = ""
            currentcharcount = "0;"; = ""
        } = ""
        currentcharcount++; = ""
        currentcharitem++; = ""
        trace(_root.mysentences.length); = ""
        trace(_root.mysentences[0]); = ""
        trace(_root.mysentences[1]); = ""
        trace(_root.mysentences[2]); = "" [ = ""
            code
        ] = ""
        this = ""
        outputs = ""
        the = ""
        following: = "" [code = ""
            lang = "c"
        ] = ""
        3 = ""
        you = ""
        got = ""
        far = ""
        so = ""
        we = ""
        reckon = ""
        that = ""
        could = ""
        be = ""
        curious = ""
        enough = ""
        to = ""
        learn = ""
        a = ""
        little = ""
        more, = ""
        we? ll = ""
        contact = ""
        shortly = ""
        answer = ""
        any = ""
        que = ""
        tions = ""
        may = ""
        have. = ""
        split = ""
        string = ""
        into = ""
        sentences = ""
        by = ""
        max = ""
        line = ""
        length = ""
        and = ""
        use = ""
        word - wrapping. = ""
        var = ""
        personalmessage: string = "You got this far so we reckon that you could be curious enough to learn a little more, we?ll contact you shortly to answer any questions you may have."
        _root.myarray = "new"
        array(); = ""
        ");="
        " _root.mysentences="
        new " currentcharstring:string="
        " maxlength:number="
        60;
        " for="
        " (var="
        " i="
        0;
        " i<_root.myarray.length;="
        " i++="
        " )="
        " (currentcharstring.length<maxlength)="
        " " = ""
        ";="
        " ((currentcharstring.length="
        ">= (maxLength-1)) || (i==(_root.myArray.length-1))) {
        _root.mySentences.push(currentCharString); currentCharString = "";
    }
    else currentCharCount++;
} & lt;
/maxlength)>

trace(_root.mySentences.length);
trace(_root.mySentences[0]);
trace(_root.mySentences[1]);
trace(_root.mySentences[2]);

This outputs the following:

Search and Replace Anchor Href using Javascript

Thu, 29 Apr 2010 10:04:50 +0000

I have a site that is under development and it was made really badly so I needed a quick way to replace all anchors on page to the relevant path.

The problem is because it was a testsite that lived away from the public facing domain, the anchors had to be changed because they were all coded in as absolute paths.

I included a JavascriptDebug file and put the following in there:

Error 29506 while installing SQL Server Management Studio Express

Wed, 28 Apr 2010 16:39:03 +0000

I was trying to install Microsoft SQL Server Management Studio Express (what a long name) on a machine and kept getting error 29506 right near the end with a Rollback action thereafter.

To get this program installed you will need to run Command Prompt as Administrator and then run the MSI (installer) from there.

Navigate to C:\Windows\System32\ then right click on cmd.exe and select Run as Administrator. Once the console has loaded, you can “cd” to the directory and then run the installer from there.

Swap HTML Elements Using Javascript

Mon, 26 Apr 2010 12:06:00 +0000

It is quite easy to use javascript to swap between divs or any other html dom elements.
Using the function below you can pass the id of the element to show and to hide.

function swapDivs(show, hide){
    document.getElementById(show).style.display = "block";
    document.getElementById(hide).style.display = "none";
}

A PHP Mail Class

Mon, 26 Apr 2010 11:59:42 +0000

Below is a Mail class I created in PHP, it requires 4 arguments on initiation of the class via the constructor and uses the method ->send() to send the created mail once complete.

class Mail {
var $to;
var $subject;
var $content;
var $headers;

function Mail($to, $subject, $content, $from){

$this->to = $to;
$this->subject = $subject;
$this->content = $content;
$this->headers = "Content-type: text/html; charset=iso-8859-1\r\nFrom: $from";

$this->content = "".$content."";
}

function send(){
return mail($this->to, $this->subject, stripslashes($this->content), $this->headers);
}
}

iTunes keeps maximizing!

Mon, 26 Apr 2010 10:58:48 +0000

Oh my goodness, this can be an annoying issue with iTunes.

The problem is: iTunes will restore itself or maximize itself all the time every 20 or so seconds without being clicked on, it will also get main focus and whatever you were doing will have to wait!

I solved this by right clicking on the iTunes program icon where I launch it from and selecting Properties, then selecting “Compatibility” then making sure “Run this program as an administrator” was checked.

Replace newline break in Excel

Fri, 23 Apr 2010 17:32:31 +0000

Ever needed to find & replace the newline character in a large excel document?

In the Replace Dialog (Ctrl+F)
Find: Hold down [alt] and type 010 on the numeric keypad.
Replace: Replace with a space " " (without quotes)

PHPExcel Class Usage

Fri, 23 Apr 2010 16:03:05 +0000

I just finished adding an export xls (excel) export feature to a web application.

I used the PHPExcel Class from CodePlex, its really great to work with – as far as the world of exporters go that is.

In the example below the “exportCheckpoints” function requires an imploded string seperated as “|||||”. Hopefully it gives an example of how easy it “could” be to export something from mysql to excel using php.

unexpected T_IF

Thu, 22 Apr 2010 14:48:41 +0000

Getting “Parse error: syntax error, unexpected T_IF” ?
Check if the preceeding line ends with a ;

Worst Websites of All Time

Mon, 19 Apr 2010 10:03:29 +0000

http://www.arngren.net/

http://www.lingscars.com/

http://www.theworstwebsite.com/ – beware, alert boxes coming!

http://havenworks.com/

http://www.msy.com.au/

http://www.5safepoints.com/

http://www.pixyland.org/peterpan/

http://www.aiseikai.or.jp/

Set line leading / line spacing in flash actionscript 2

Fri, 16 Apr 2010 16:14:40 +0000

This is how to add text leading using Actionscript 2 for Flash.

var txtFormat:TextFormat = new TextFormat();
txtFormat.leading = 5; // change this to whatever you need it to be
ttt.setTextFormat(txtFormat);
ttt2.setTextFormat(txtFormat);

There is also a GUI way of doing this:

Select your textfield and and under the paragraph section, set the top/right hand icon (Line Spacing) to whatever you like.

MySQL Main Query Types used in PHP to select, insert, update and delete data

Fri, 16 Apr 2010 11:25:03 +0000

MySQL Main Query Types

SELECT

SELECT * FROM tablename

INSERT

INSERT INTO tablename (col1, col2, col3,..) VALUES (val1, val2, val3,...)

UPDATE

UPDATE tablename SET `col1`=`val1`, `col2`=`val2`, `col3`=`val3`,...

DELETE

DELETE FROM tablename WHERE `col4`=`val6`

Note

You will use a lot of WHERE clauses as well along with the above.

e.g.

SELECT * FROM tablename WHERE `id`='15'

In PHP

Calling to MySQL is really easy in PHP, just use the mysql_query() function.

e.g.

mysql_query("SELECT * FROM tablename")
$query = mysql_query("SELECT * FROM tablename");
while ($result = mysql_fetch_object($query)) {
  echo $result->aColumnNameInMysql;
}

Connect to mysql database from php

Fri, 16 Apr 2010 11:05:03 +0000

If you need to connect to a mysql database from php you can do it like this:

<?php

$DBH = 'localhost';
$DBU = 'root';
$DBPWD = 'password';
$DBN = 'petstore';
$conn = mysql_connect($DBH, $DBU, $DBPWD) or die ("Error: Could not connect to database.");
mysql_select_db($dbname);

This allows you to make a connection to the mysql database and gets it ready for you to make queries and manipulate the data.

htaccess file and error 500 internal server error

Wed, 14 Apr 2010 13:17:50 +0000

I have a question for anyone that can answer it:

I create an .htaccess file in the root of a subdomain, but if I enter either of these two lines I get an erro 500 Internal Server Error:

php_flag magic_quotes_gpc off
php_flag register_globals off

Any suggestions anyone?

Quake 4 – Fatal Error: could not create destination file

Fri, 09 Apr 2010 14:33:37 +0000

If you get an error message similar to this one when trying to run Quake 4…

Fatal Error: could not create destination file C:/Program Files (x86)/id Software/Quake 4 Multiplayer Demo/q4mp/gamex86.dll

…then you should run the exe as Administrator.

So Right-click, “Run as Administrator” and all will be sorted.

phpMyAdmin – Invalid field count in csv input on line 1

Fri, 09 Apr 2010 10:59:45 +0000

I was trying to import a massive csv dataset into phpMyAdmin and it kept throwing error:
Invalid field count in csv input on line 1

This is quite annoying as I followed all the usual steps as per normal.

To solve this I had to do the following:

Import
Browse for your CSV file.
Select CSV using LOAD DATA (rather than just CSV)
Change “Fields terminated by” from “;” to “,”
Make sure “Use LOCAL keyword” is selected.
Click “Go”

Done!

Choosing a programming IDE

Wed, 07 Apr 2010 11:40:57 +0000

This is somewhat of a debatable topic, but it has come up a lot of times without any real final clarity, so I will try and cover it all.

Lets begin by explaining exactly what an IDE is and then we can move onto the more debated areas of choosing the right one for you.

An IDE stands for “Integrated Development Environment” and is often used by programmers when creating their applications. It can be quite a different thing according to lots of factors including language, preference and perhaps a biased opinion.

Double border in CSS

Tue, 30 Mar 2010 09:27:51 +0000

CSS allows you to add a border to almost all html elements. This is one of many CSS techniques you can use to enhance your web pages, along with using CSS background image data for more advanced styling.

If you would like a double border you can use CSS like this: style="border:double"

For more CSS styling options and techniques, you might also be interested in exploring how Google uses background images on their pages.

[Exception… “Could not convert JavaScript” nsresult: “0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)”

Tue, 30 Mar 2010 08:38:14 +0000

What the heck is..

uncaught exception: [Exception… “Could not convert JavaScript argument arg 0 [nsIDOMHTMLDivElement.appendChild]” nsresult: “0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)” location: “JS frame :: PATH_TO_MY_JAVASCRIPT_FILE :: THE_METHOD_NAME :: line #” data: no]

For me it was just an appendChild() that was causing the problems. You can always try the innerHTML+= way if all else fails 😉

Error 1046: Type was not found or was not a compile-time constant: Event.

Mon, 29 Mar 2010 20:10:48 +0000

Error 1046: Type was not found or was not a compile-time constant: Event.

You need to import the Event class!

import flash.events.Event

Add a date to a date in Actionscript 2

Fri, 26 Mar 2010 20:19:42 +0000

I needed to work out a date range according to the date 3weeks away from the current date.
After a bit of thinking, I found that it’s actually quite easy to achieve.

var theDate:Date = new Date();
dateDay = theDate.getDate();
dateMonth = theDate.getMonth();
dateYear = theDate.getFullYear();

var theDate2:Date = new Date(dateYear,dateMonth,dateDay);
theDate2.setDate(theDate2.getDate() + 21);
dateDay2 = theDate2.getDate();
dateMonth2 = theDate2.getMonth();
dateYear2 = theDate2.getFullYear();

The above code gets the current date and adds 21days/3weeks to it.
Remember that if you use getMonth to output the final month number, you will want to add 1 to it as it starts at 0;
Example:
dateMonth2 = theDate2.getMonth()+1;
So you would do it like this:
theDate2.getDate() +"/"+ (theDate2.getMonth()+1) +"/"+ theDate2.getFullYear();

Add a month to selectable date range – Date Chooser – Actionscript 2

Mon, 22 Mar 2010 12:40:20 +0000

I have been working on a project where I need to select a date range starting today and ending a month from now, so the user cannot select anything in the past or over a month from now.

This is how I did it:

There is an instance of DateChooser on the stage with Instance Name “calDate”.

var todayDate:Date = new Date();
dateBeginDay = todayDate.getDate();
dateBeginMonth = todayDate.getMonth();
dateBeginYear = todayDate.getFullYear();

if ((todayDate.getMonth()+1)==12) {
  dateEndDay = todayDate.getDate();
  dateEndMonth = 1;
  dateEndYear = todayDate.getFullYear()+1;
} else {
  dateEndDay = todayDate.getDate();
  dateEndMonth = todayDate.getMonth()+1;
  dateEndYear = todayDate.getFullYear();
}
calDate.selectableRange = {rangeStart: new Date(dateBeginYear, dateBeginMonth, dateBeginDay), rangeEnd: new Date(dateEndYear, dateEndMonth, dateEndDay)}

hitTest and Actionscript2

Fri, 19 Mar 2010 11:42:31 +0000

if (mc.hitTest(_root._xmouse, _root._ymouse, true))) {
  trace("hitTest Run");
}

127.0.0.1:4664 and Google Desktop Search

Wed, 17 Mar 2010 15:09:08 +0000

Recently I checked my website stats and saw I had a few hits from “127.0.0.1:4664” and wondered to myself, what the heck is that? Am I looking at my own site from a localhost? Why am I getting backlinks from my local computer to my site.

After searching around a bit I found out that port 4664 is used by Google Desktop Search and when I typed in certain queries into Google it also returned items from my desktop search.

Limited numeric input in flash actionscript 2 textfield

Tue, 16 Mar 2010 12:42:46 +0000

If you want to only show numeric characters in a textfield in flash actionscript you can use the following code:

myTextField.restrict = "0-9";

Embed pound symbol (£) in flash textfield

Wed, 10 Mar 2010 13:55:36 +0000

If you use a dynamic textbox in Flash and you want to embed the British Pound symbol (£) then you will want to also embed the “Latin I” glyphs with your textfield.

Enable / Disable Cursor Hand in Actionscript 2

Mon, 01 Mar 2010 14:40:40 +0000

If you have a movieclip that by default has the hand cursor showing on RollOver and you don’t really want this, you can disable it by doing the following:

myMC.onRollOver = function() {
    this.useHandCursor=false;
}

So the main code here is: this.useHandCursor=false;

False disables it and true shows it.

USB Device Not Recognized! in Windows

Thu, 25 Feb 2010 09:23:59 +0000

Believe it or not, this one is super easy to fix!

It’s actually a temporary problem with your motherboard, all you need to do is:

turn off your computer
if it’s a desktop then unplug it from the wall/powersupply
if it’s a laptop then remove the battery
let it sit for a minute
plug it all in again
reboot
VOILA!

No need to uninstall/reinstall drivers or anything!

Calling event functions from movieclips in actionscript 2

Wed, 24 Feb 2010 17:41:03 +0000

In a flash movie I usually have a frame of actionscript that controls all elements in the file to keep everything in one place.

Sometimes I have an onPress(etc) function that refers to something happening in the scene when something is pressed, but what happens if we want another element to refer to that event for some reason?

Here’s an example of that code without anything “flashy”:

_root.myMC.onPress = function() {
  //code goes here
}

..and here’s our slightly more intersting flashy version:

Sudo install OpenGL & SDL on Ubuntu

Mon, 22 Feb 2010 11:57:00 +0000

A quick and easy way would be to type the following in one line with single spaces in the Terminal.
This way of installing OpenGL and SDL libraries only applies to Ubuntu.

sudo apt-get install
nvidia-glx-new-dev
libglew1.4-dev
libsdl1.2-dev
libsdl-ttf2.0-dev
libsdl-image1.2-dev
libsdl-mixer1.2-dev

How To Modify Hosts File On Windows

Fri, 19 Feb 2010 09:15:41 +0000

The hosts file is located at the following address:

C:\windows\system32\drivers\etc

%systemroot%\system32\drivers\etc
But you will need to open Notepad with “Run as Administrator” first and then open it through there otherwise it will give a permissions problem

Get all directories in PHP

Wed, 17 Feb 2010 13:54:23 +0000

I think this may be the fastest way to get a list of all the directories in a given folder/directory using PHP.

$directories = array_filter(glob('*'), 'is_dir');

..and of course, you can also add a path to it if you need to:

$directories = array_filter(glob($myPath.'*'), 'is_dir');

Security error: securitySandboxError with Flash

Wed, 17 Feb 2010 13:12:21 +0000

You have a flash uploader and you get this error:

security error: securitySandboxError

This means that the flash is not trusted by the domain and you have to place an xml file in the root of the domain.

The file is called “crossdomain.xml” and this is what should be inside it:

Component Inspector in Flash has ISSUES!

Thu, 11 Feb 2010 13:14:32 +0000

I discovered a very annoying bug in the Flash IDE a little while ago, and it has happened to me quite a few times.

Today it happened again and so I write this post..

While in the Flash IDE you select a component on the stage, then you click “Component Inspector”.This opens up into a modal window which is nice and everything BUT….
…..if you then give focus to another program and then try click back into flash, it hides the “Component Inspector” modal window but still keeps focus on it, so basically, you can’t use the program(Flash IDE) / save your file / or even close the program!

Close/Delete Google Checkout Account

Mon, 08 Feb 2010 12:46:20 +0000

I have used Google Checkout to receive payments in the past and have had problems with some clients not paying and blaming it on Google Checkout that the money did not go through (like the guys over at Peartree DMS).

I decided that this account was not worth the trouble anymore and wanted to close my account.

Warning: mysql_affected_rows(): supplied argument is not a valid MySQL-Link resource

Tue, 02 Feb 2010 10:54:35 +0000

Warning: mysql_affected_rows(): supplied argument is not a valid MySQL-Link resource

You have just gotten a warning when trying to check if an inserted row was successful but when calling mysql_affected_rows(mysql_query(“INSERT INTO……”)) you get a warning telling you that the supplied argument is not a valid MySQL-Link resource.

This is because mysql_query INSERT actually returns true or false and not a resource id.

Capitalize First Letter in Word – Actionscript 2

Mon, 01 Feb 2010 15:06:09 +0000

You have a string and you want to capitalize the first character but have the rest of the word in lowercase.

DO THIS!

myStringVar = myStringVar.substring(0, 1).toUpperCase()+myStringVar.substring(1);

HP Pavilion Laptop Madness

Thu, 28 Jan 2010 17:12:48 +0000

I have got an HP laptop and have started experiencing problems with it starting up for the past few months, it is only about 1.5years old and is supposed to be a decent one.

It is an HP Pavilion dv9700 by the way..

Today the damn thing just didnt want to startup and eventually after trying every trick in the book I got it to boot into Degugging Mode in Windows Vista.. What a nightmare!!!!

Why you should use OpenGL and not DirectX

Wed, 27 Jan 2010 12:58:10 +0000

Below is a very interesting article I found that proves all the myths about DirectX being better than OpenGL, a very well written paper describing it best.

Thanks for that guys at Wolfire.com!

http://blog.wolfire.com/2010/01/Why-you-should-use-OpenGL-and-not-DirectX

What does FILE in php mean?

Tue, 26 Jan 2010 17:04:06 +0000

In php there are a few magic constants and I find FILE to be a very useful one.

It returns the full path and filename of the file in question.

Take a look at the PHP Manual – Magic Constants for more information on the others.

Woopra Failed to Connect?

Tue, 26 Jan 2010 13:33:22 +0000

I have used Woopra for a few months now and have started seeing this warning/error almost everyday now:

Could not enable live functionality at this time. Click to reconnect.

If you click the text/warning/error it seems to go away… Anybody konw what’s really going on under the cover?

What happened:

Change PHP Session Time

Mon, 25 Jan 2010 14:28:47 +0000

The default time for a php session is 1440 seconds.

You can change it by doing the following:

ini_set("session.gc_maxlifetime",1440);

You can obviously adjust the second parameter (1440) to anything you like to change the timeout limit.

Stop mouse click in browsers

Fri, 08 Jan 2010 17:22:01 +0000

There have been multiple ways to stop your user/s from right clicking on your site, but many of them now fail due to the way firefox’s contextual menu loads.

Below is an example of how to do it:

function _c(e) {if (document.all) {if (event.button==2||event.button==3) {return false;}} else {if (e.button==2||e.button==3) {e.preventDefault();e.stopPropagation();return false;}}if (e.which) {}}if (document.all){document.onmousedown=_c;}else{document.onclick=_c;document.ondblclick=_c;}

..and here is the full working example in a webpage:

<script><br />
function _c(e) {if (document.all) {if (event.button==2||event.button==3) {return false;}} else {if (e.button==2||e.button==3) {e.preventDefault();e.stopPropagation();return false;}}if (e.which) {}}if (document.all){document.onmousedown=_c;}else{document.onclick=_c;document.ondblclick=_c;}<br />
</script>

tester

Microsoft apps never care!

Fri, 08 Jan 2010 15:57:22 +0000

I often seem to have this issue when dealing with Microsoft software.
You click “Cancel” and it just carrys on going, so you click it again a few more times and instead of it just stopping in it’s tracks, decides to rather tell you it’s cancelling and then shows a cancelling dialog box for the next 10 minutes!

Cummon guys, that’s not very professional!

Place HTML Div on top of Flash

Fri, 08 Jan 2010 14:23:23 +0000

If you have ever tried to place a div or similar HTML element on top of a swf flash object you will know that it always tries to take precedence.

You will need to do the following:

In the code for the flash in the embed area add:

wmode="transparent"

If you are using SWFObject to insert swf files you can do the following:

<script type="text/javascript">
  var so = new SWFObject("movie.swf", "mymovie", "400", "100%", "8", "#336699");
  so.addParam("wmode", "transparent");
  so.write("flashcontent");
</script>

Get current working directory of php script/application

Fri, 08 Jan 2010 14:13:59 +0000

$myPath = realpath(dirname(__FILE__));

$myPath = getcwd();

Stage align and Stage scale in actionscript 3

Fri, 08 Jan 2010 12:09:18 +0000

If you want to position the flash top/left and not have it scale when you resize it’s bounding box window, you can set the following code.

stage.align = StageAlign.TOP_LEFT;
stage.scaleMode = StageScaleMode.NO_SCALE;

For full documentation from Adobe take a look here.

Error 406?

Wed, 06 Jan 2010 17:53:41 +0000

So you received an error 406 while trying to upload a file and you have no idea to fix it!

Create an .htaccess file in the root of your local website and add the following into it:

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

Firefox error in FeedProcessor.js

Wed, 06 Jan 2010 12:30:18 +0000

[Exception… “Component returned failure code: 0x80040111 (NS_ERROR_NOT_AVAILABLE) [nsIChannel.contentType]” nsresult: “0x80040111 (NS_ERROR_NOT_AVAILABLE)” location: “JS frame :: file:///C:/Program%20Files/Mozilla%20Firefox/components/FeedProcessor.js :: FP_onStartRequest :: line 1440” data: no]file:///C:/Program%20Files/Mozilla%20Firefox/components/FeedProcessor.jsLine 1440

So what the heck does that all mean?
Basically, there is an exception error on like 1440 of the local Firefox javascript file “FeedProcessor.js”.

The line in question is as follows:
channel.contentType = “application/vnd.mozilla.maybe.feed”;
The whole section of code reads as follows:
// nsIStreamListener

mySQL select multiple ids

Fri, 18 Dec 2009 12:44:51 +0000

SELECT * FROM tablename WHERE `active`='1' AND `id` IN ('107' , '125' ) ORDER BY `id` DESC LIMIT 12`

Force Download in PHP

Wed, 16 Dec 2009 18:00:30 +0000

This script works in all browsers, including Internet Explorer! 🙂

if (strstr($_SERVER['HTTP_USER_AGENT'],"MSIE")) {
  header("Pragma: public");
  header("Expires: 0");
  header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
  header("Cache-Control: private",false);
  header("Content-Type: application-download");
  header("Content-Disposition: attachment; filename=\"".basename($filename)."\";");
  header("Content-Transfer-Encoding: binary");
  header("Content-Length: ".@filesize($ab_file));
  set_time_limit(0);
} else {
  header("Content-type: application-download");
  header("Content-Length: ".filesize($ab_file));
  header("Content-Disposition attachment; filename=".$filename);
}
readfile($ab_file);

Remove an onRelease Handler

Wed, 16 Dec 2009 13:07:05 +0000

After creating a onRelease handler in Actionscript 2 as follows:

myMovieClip.onRelease = function() { doWhatever(); }

..you then want to remove the handler for whatever reason, you can remove it like this:

delete myMovieClip.onRelease;

shortText function toggler in php

Tue, 15 Dec 2009 13:49:33 +0000

I often have to show a shortened version of a news item and then a link to show the entire news article or whatever.

Here’s a way to get that short text!

function shortText($text, $length) {
  if( strlen($text) > $length ) return substr(preg_replace("/(<\/?)(\w+)([^>]*>)/", "", $text), 0, $length)."?";
  return preg_replace("/(<\/?)(\w+)([^>]*>)/", "", $text);
}

PHP – file() lines

Tue, 15 Dec 2009 11:22:24 +0000

$lines = file('all-words.txt');
foreach ($lines as $line_num => $line) {
  echo "Line number ".$line_num;
}

Windows Live Writer – Beta2

Mon, 14 Dec 2009 12:56:17 +0000

Start writing content to your blogs from your Windows Desktop now.

No need to login to your wordpress backend to post items anymore, there is now a decent desktop application that allows you to do exactly that!

I have looked at it before but not until recently when Beta2 came out did I gain more interest for it.

The WordPress functionality added is what got me going and now I am able to post directly! Excellent 🙂

Reported Attack Site!

Fri, 11 Dec 2009 10:35:28 +0000

What the heck is that?

So you’ve just visited a website using Mozilla Firefox and this message has popped up telling you that the site looks suspicious.

Usually the site has been marked as a possible virus containing website and Firefox will show you this message attempting to protect itself against Malware, Spyware or other forms of Viruses.

There are occasions when this is mearly a warning and not to be taken as concrete evidence of viruses or impending browser/computer doom!

Simple HEX Colour Values

Thu, 10 Dec 2009 17:25:54 +0000

Actual Display Colour	HEX Colour
	#000000
	#FF0000
	#00FF00
	#0000FF
	#FFFF00
	#00FFFF
	#FF00FF
	#C0C0C0
	#FFFFFF

Send Email PHP Function

Thu, 10 Dec 2009 17:07:37 +0000

Ever find yourself typing the headers into the php mail() function over and over again?

Try using a standard function and calling it when you need to send mail.

function sendEmail($subject,$content,$from,$to){
  $header = "Content-Type: text/html; charset=iso-8859-1\nFrom:$from";
  if( mail($to, $subject, $content, $header) );
}

mySQL Development Tools

Wed, 09 Dec 2009 11:40:55 +0000

I came across a very interesting article about mySQL Development Tools.

http://www.smashingmagazine.com/2009/03/25/mysql-admin-and-development-tools-round-up/

1180: Call to a possibly undefined method getURL. Actionscript 3

Mon, 07 Dec 2009 12:05:02 +0000

Hello all actionscripters, you can’t use getURL anymore in Actionscript 3.

Below is how you should now start doing it:

var request:URLRequest = new URLRequest("/");
try { navigateToURL(request, '_blank');}
catch (e:Error) { trace("Error occurred!");}

Online Flash IDE Anybody?

Thu, 03 Dec 2009 17:44:38 +0000

Anyone up for an online Flash IDE?

Take a look at this:
http://antimatter15.com/ajaxanimator/build/

Nice work!

Papervision Event Listener Idea

Thu, 03 Dec 2009 10:12:11 +0000

The problem:
While working on a Papervision3D Flash Project I had a problem where a back button that sits above the 3d canvas and acts as a main navigational item was required to change Events according to where the site was in 3d space at the time.

The solution:
Everytime I’m about to add a new EventListener to the back button movieclip I call the function “delBB()” and then add my event listener using addBB(with the event here).

Don’t cache my swf files!

Wed, 02 Dec 2009 16:38:37 +0000

I often have issues where ‘dumb browsers’ cache my published swf files and when they dynamically populate they don’t always update.

This is SUPER annoying and I have found a solution.

I will demonstrate the technique with a LoadsVars example

var nc = Math.floor(random(1000000) / random(1000));
var send_lv:LoadVars = new LoadVars();
send_lv.sendAndLoad(_root.siteURL+"profile.php?action=showallimages&amp;nc="+nc, result_lv, "POST");

So let me describe what is happening here.

The really ‘dumb browsers’ like IE7 in this case decide that seeing as the URL in question has the exact same name, it will be clever and just use the last version it saw and be totally lazy and not attempt to get the data again. But the really stupid part about this is that most of the time the results are DYNAMIC and will always return a different result.

Clear an array in Actionscript 3

Wed, 02 Dec 2009 11:12:07 +0000

I personally really like this way of clearing an array’s elements:

Declare your array to use:

var myArray:Array=new Array();

Add elements:

for (var i:Number;i<10;i++) {
  myArray[i] = "an item";
}

Clear the array:

Change combobox font size in Flash Actionscript

Mon, 30 Nov 2009 11:05:54 +0000

Ever needed to change the font size of a standard flash combobox component?

You will need to give it an instance name e.g. “myCombobox” and then add the following code:

myCombobox.setStyle("fontSize", 10);

Wordwrap that PRE!

Mon, 23 Nov 2009 16:00:00 +0000

Ever used a <PRE> in a limited width div container? You will notice that the line gets cut off almost as if word-wrap was not enabled.

To correct this you can add the following code into your CSS file.

pre{
  white-space: pre-wrap; /* CSS2.1 compliant */
  white-space: -moz-pre-wrap; /* Mozilla-based browsers */
  white-space: o-pre-wrap; /* Opera 7+ */
}

This code was originally found somewhere else online but I found it really useful so reposted it!
If you’re the original author then comment and let us know 🙂

Barclays ePDQ Payment Gateway

Mon, 23 Nov 2009 15:32:25 +0000

Hello all!

Today we will be talking about Barclays online payment gateway valled ePDQ.
You can take a look at what they have got to say by clicking here to view Barclays’ site or you could keep reading 🙂
Well, for all you php guys out there, this post if for you!

Barclays ePDQ encrypts your data string of products in your basket and returns a result that is sent with your HTML form on your site.

BrainWHAT? programming language

Mon, 23 Nov 2009 15:05:45 +0000

I came across a programming language today that I have never heard of. Go take a look over here:

http://en.wikipedia.org/wiki/Brainfuck

Transparent swf in html

Mon, 23 Nov 2009 14:10:59 +0000

So you have now placed a swf file into your html page and you want to be able to see through it.

Lucky for you, this is a very easy thing to do!

The following code does the trick:

<object data="flash/home_side_left.swf" type="application/x-shockwave-flash" width="40px" height="550px"><param name="movie" value="flash/home_side_left.swf" /><param name="bgcolor" value="#ffffff" /><param name="wmode" value="transparent" /><param name="allowScriptAccess" value="always" /></object>

Notice that by just adding the wmode and setting it as ‘transparent’ does everything for you!

Constant updates?

Fri, 13 Nov 2009 10:29:19 +0000

I just hate it how everything always wants to update… and then restart all the damn time!

First things first:

This pops up telling me it’s doing a 309.6MB Adobe Reader Update! Which to me is just crazy… Surely the constant updates shouldn’t be a million times larger than the actual initial install file for the application?

I just click Cancel and then do this..

Not a minute later and this little guy pops up!
Will it ever end????

Share the mouse and keyboard!

Fri, 13 Nov 2009 10:23:42 +0000

A very interesting project I found this morning, take a look at this one!
http://synergy2.sourceforge.net/

What is CWS>+?

Thu, 12 Nov 2009 17:25:37 +0000

So what the heck kind of file starts with the characters “CWS>+” ?

That would be a flash swf file!

Papervision error 1046

Thu, 05 Nov 2009 10:51:32 +0000

Error: “1046: Type was not found or was not a compile-time constant: InteractiveScene3DEvent.”

I got this this morning when I opened up a project I have been working on. I was using the Flash IDE to compile and FlashDevelop to code in as I am not the biggest fan of the Flash IDE for coding in….. Who is? Right?

Anyways… I tried to publish my swf and I got loads of errors like the one above. So after looking into what was going on I discovered that half of my papervision classes were missing! How the heck that happened I have no idea, as I store them per project basis and not as one standard import.

How to Save a Dreamweaver document as UTF8!

Wed, 04 Nov 2009 10:48:12 +0000

Today I tried to save arabic text inside a javascript file and on saving encountered a dialog box asking me to first convert the document to UTF8.

Why it didnt just do it for me I’ll never know, so I had to do it myself.

If you encounter this then do the following to convert the document:

Click on the Modify main menu item and select Page Properties.
Change the Encoding/Document Encoding dropdown to say “Unicode (UTF-8)” or “Unicode 4.0 (UTF-8)”
Click OK
Save the document

16000 Limit!

Tue, 03 Nov 2009 12:20:15 +0000

Today I discovered that Flash truly has a limit!

Take a look at the adobe knowledge base for more information…

http://kb2.adobe.com/cps/144/tn_14437.html

htaccess ErrorDocument

Mon, 02 Nov 2009 16:53:37 +0000

Create a file called .htaccess in the root of your public_html/htdocs of your domain.

Inside add the following text:

Options +FollowSymLinks
AddDefaultCharset UTF-8
RewriteEngine on
Options +FollowSymLinks
AddDefaultCharset UTF-8
RewriteEngine on

ErrorDocument 404 /index.php
ErrorDocument 301 /index.php

With the index.php files being the pages that get redirected to.

How to correctly form HTML

Mon, 02 Nov 2009 16:49:57 +0000

<!DOCTYPE html PUBLIC ?-//W3C//DTD XHTML 1.0 Strict//EN? ?http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd?>
<html xmlns=?http://www.w3.org/1999/xhtml?>
 <head>
 <meta http-equiv=?Content-Type? content=?text/html; charset=UTF-8? />
 <script type=?text/javascript? src=?javascript/javascriptfilename.js?></script>
 <title>Title goes here</title>
 <link href=?stylesheetname.css? rel=?stylesheet? type=?text/css? />
 </head>
 <body>
 Page content goes here
 </body>
</html>

Trying to get variables into flash from the browser!

Mon, 02 Nov 2009 16:40:21 +0000

Ever wondered how to get variables from an html page to a flash element?

Well, it’s quite easy using the following actionscript 2 example:

I use javascript to embed my flash elements:
_
<embed src="somefilename.swf?varname=varvalue&vartwo=var2value" width="550" height="400"></embed>_

Now in Flash I can just call:

_root.varname and it will give us `varvalue`
_root.vartwo will give us `var2value`

Wasn’t that easy?

Flash Tweening

Tue, 20 Oct 2009 21:37:58 +0000

tween is an actionscript class and can be used after importing the core files.

import mx.transitions.Tween;
import mx.transitions.easing.*;
//Tween( obj:Object, prop:String, func:Function, begin:Number, finish:Number, duration:Number, useSeconds:Boolean);

e.g.

var myRot:Tween = new Tween(myText, "_rotation", Elastic.easeOut, 0, 360, 3, true);

Cube Desktop on Ubuntu

Tue, 20 Oct 2009 21:37:33 +0000

Alright, so I run Ubuntu 7.10 and use the Desktop Effects via compviz, anyhow, I could get the 2d workspace but really wanted the 3d cube, even if I set up 4 desktops, it would still only show 2 sides of the cube(aka not a cube).

The solution is: In Terminal do: gconftool-2 --type int --set /apps/compiz/general/screen0/options/hsize 4

😉

Animate with Actionscript [part1]

Tue, 20 Oct 2009 21:37:03 +0000

// Created by Andrew Odendaal
//
// :: DESCRIPTION ::
// Animate a ball moving to the top
// of the screen/stage and back again
//
// :: HOW TO USE ::
// create a circle shape, convert to a movieclip(mc) and
// place the registration point at the bottom center.
// give the circle mc an stage instance name of 'ball'.

var ball:MovieClip;
var initBallY:Number = _root.ball._y;

onEnterFrame = function() {
  if (_root.ball._y < 2.31) {
    _root.ball._y = initBallY;
  } else {
    _root.ball._y=_root.ball._y-10;
  }
}

Kill Adobe Updater

Tue, 20 Oct 2009 21:35:42 +0000

So adobe updater keeps doing updates eventhough you’ve said ‘NEVER DO IT AGAIN!!!’.
The fix is to physically remove the dir with the info in.
On a windows system go to ‘c:\program files\common files\adobe', there is a nasty little folder called UPDATER5 in there that you can DELETE!
PROBLEM SOLVED 😉

Apache Cannot be Run. Another web server is using the web port or port is blocked by firewall.

Tue, 20 Oct 2009 21:35:04 +0000

Tried to start EasyPHP: “Apache Cannot be Run. Another web server is using the web port or port is blocked by firewall.”

I was running Skype! And it was blocking the using the port.
Check in options->advanced->connection for the setting on port 80.

Another way to stop this from happening and solve the problem quicker is to go into the “Configuration->EasyPHP” [Ctrl+E] and make sure that the “Check server’s TCP port before starting” checkbox is not checked. This forces apache to just start and seems to work just as well!

How to load xml into flash using actionscript 2

Tue, 20 Oct 2009 21:33:38 +0000

Create an xml object:

var myXmlObject = new XML();

Perform action when xml file has been loaded:

myXmlObject.onLoad = function(success) {
  if (success) trace("XML File has been read.");
}

Load the xml file into the object:

myXmlObject.load("myXmlFile.xml");

TypeError: node is null message=node is null

Tue, 20 Oct 2009 21:33:01 +0000

The following error message occurs in Firefox 3 when using Firebug.
TypeError: node is null message=node is null
The error can be tracked back to script tags being in the head of the document instead of where they’re needed, an example would be with the ShareThis control/component that is often added to blogs and etc.

Cant start your browser?

Tue, 20 Oct 2009 21:32:24 +0000

Cant start your browser?
Try checking if any torrent apps are running.. Close them and retry.

How to Temporarily Edit the Text of Any Website

Tue, 20 Oct 2009 21:31:38 +0000

Have you ever wanted to temporarily edit a webpage displayed in Chrome or another browser?

How it works

Let’s take a look at the Google homepage quickly.

Now, after we apply our little “page hack”, let’s look at it again!

How to temporarily edit a webpage

Go to a website of your choice that you would like to edit.
Enter the following javascript into the address bar:

javascript:document.body.contentEditable="true"; document.designMode="on"; void 0

PHP __autoload function

Tue, 20 Oct 2009 21:30:51 +0000

When PHP encounters a class that hasn’t been defined yet, you can use __autoload to automatically add them instead of including masses of included at the top of your files.

e.g.

function __autoload($class_name) {
  require_once $class_name . '.php';
}

IE6 on Vista?

Tue, 20 Oct 2009 21:30:02 +0000

I find myself constantly fighting the microsoft battle of making things work in their browsers (thanks guys).

On one of my machines I have Vista installed and needed to test a newly created site that apparently had some issues under Internet Explorer 6.

HOWEVER, to my horror IE6 was unable to run on Vista. Once again, thanks Microsoft for making life difficult for everyone out there!

After much grief, pain and agony with a million attempts to get it to run I stumbled upon a really great tool called IETester made by DebugBar.

Guillotine-Bug? Bug

Tue, 20 Oct 2009 21:28:59 +0000

Yes, it’s called a Guillotine-Bug and it’s yet another bug IE users get to look forward too 😛

So how does it work?
Basically, the hasLayout messes around and elements become invisible and visible according to random things. Rather silly, but a bit of a bitch to initially figure out.

So how do you fix it?

Try this:

in your css file add:

* html .container {height: 1%;}
.container:after {
  content: '.';
  display: block;
  height: 0;
  clear: both;
  visibility: hidden;
}

then apply to all elements that have nested floats.

Sending data from javascript to php

Tue, 20 Oct 2009 21:27:47 +0000

If you ever find yourself needing to do some ajax and in turn sending strings of characters via javascript then you should really try encodeURIComponent() to wrap your strings in. The function escape() can also be used, but I would not recommend it as encodeURIComponent() is better, it also escapes your usual ampersand ajax limiters which solved me quite a bit of pain.

What is Eb in firebug?

Tue, 20 Oct 2009 21:25:55 +0000

Gmail produces the following error/warning in firebug.

Eb is not defined

function Bb(a){if(a[sb]&&a[sb](daa)){var'ents)};f.x2b=c;f.B2b=b;f.y2b=a;return f}

I initially started seeing this while while on clients’ websites, but can now say it’s a gmail thing. So don’t stress.. 😉

Add TinyMCE code button

Tue, 20 Oct 2009 21:24:27 +0000

I had quite a few problems adding the htmlCode button to a fairly old copy of TinyMCE (I think around version 2.x).

All is resolved now and this is what I had to change:

Both changes are made in “editor_template.js” file, I also swopped the 2 files so that I could include and edit editor_template.js instead of the compressed “editor_template_src.js.

Using the advanced theme I added the following line near the top of the file:

Runtime Error! (abnormal program termination) maya.exe

Tue, 20 Oct 2009 21:21:22 +0000

The Problem

When starting Maya 8.5 an immediate error message and program termination.

Runtime Error!

Program C:\Program Filesz\Autodesk\Maya8.5\bin\maya.exe

abnormal program termination

Solution

…

Need more than hover?

Tue, 20 Oct 2009 21:20:48 +0000

I had a hover effect on an html input element but also needed to have an active state.
The css was like this for the inputs in mention:

.contactformdiv input:hover, .contactformdiv textarea:hover {
  background-color:#fff;
}

It was simple, I just added a focus…

.contactformdiv input:hover, .contactformdiv textarea:hover, .contactformdiv input:focus, .contactformdiv textarea:focus {
  background-color:#fff;
}

Getting an internet connection under VirtualPC running Windows XP and Internet Explorer 7

Tue, 20 Oct 2009 21:20:21 +0000

Getting an internet connection under VirtualPC running Windows XP and Internet Explorer 7

Open the ‘settings’ of the virtual machine and select Networking -> then change Adapter1 to “Shared networking (NAT)” and it will use your local machine’s network settings.

Uppercase text in Actionscript

Tue, 20 Oct 2009 21:19:09 +0000

var lowerCase:String = "sample text";
var upperCase:String = lowerCase.toUpperCase();

Firefox too slow?

Tue, 20 Oct 2009 21:18:28 +0000

Is your Firefox starting to get realllllllly slow?

Every few months my Firefox starts dragging, so all I do is create a new profile and reimport all my bookmarks and reinstall needed addons.

For a rundown on how to create a new profile, click the following link..
http://kb.mozillazine.org/Profile_Manager

Uppercase the first character of each word in a string using PHP

Tue, 20 Oct 2009 21:13:40 +0000

You can use “ucwords()” to uppercase the first character of each word in a string.

e.g.

$myVar = 'this is a test!';
$myVar = ucwords($myVar);
// This Is A Test!

Actionscript 3 equivalent of PHP’s print_r

Tue, 20 Oct 2009 21:12:55 +0000

A brilliant version of print_r for actionscript:

http://dev.base86.com/solo/47/actionscript_3_equivalent_of_phps_printr.html

Global variables and functions in Actionscript 2

Tue, 20 Oct 2009 21:12:22 +0000

In order to reuse a variable from a different timeline within the same fla file you will need to register the inital variable or function as a _global.

Todo this as a variable:

_global.myString:String = "My String";

Todo this as a function:

_global.myFunction = function() {}

Actionscript conflicting class name

Tue, 20 Oct 2009 21:11:13 +0000

I had a problem today where I got a flash source file from one of my developers’ and I couldnt compile it because it said that there was a conflicting class name, however, it turned out to just be a timestamp issue.

Read here for more information

http://www.epresenterplus.com/blog/archives/000030.html

expecting T_PAAMAYIM_NEKUDOTAYIM

Tue, 20 Oct 2009 21:08:39 +0000

What the hey? What does this mean?

You may one day end up seeing the following error message produced by PHP and wonder to yourself:

PHP Parse error: syntax error, unexpected ‘)’, expecting T_PAAMAYIM_NEKUDOTAYIM in ///File.php on line 160

You guessed it, “T_PAAMAYIM_NEKUDOTAYIM” is not english.

It’s actually a Hebrew word meaning “unexpected” or “Twice Colon”.

It happens when PHP tries to call the “::” (double colon) which is used when identifying an uninstantiated class’ method.