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