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

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defaults read com.apple.screensaver

Step 2 – Set the idleTime

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defaults -currentHost write com.apple.screensaver idleTime 0

Step 3 – (Optional) – Undo the change

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defaults -currentHost delete com.apple.screensaver idleTime