$ [sudo] pip install mac-screensaver
$ [sudo] npm i -g mac-screensaver
$ screensaver start
$ screensaver pid
1488
$ screensaver stop
$ screensaver name
iLifeSlideshows
$ screensaver names
Random
Flurry
Arabesque
Word of the Day
iTunes Artwork
Computer Name
Shell
FloatingMessage
iLifeSlideshows
wait while screensaver is active
$ screensaver start
$ screensaver wait