Is 'sleep' based on the system clock or on time elapsed? Is 'sleep' based on the system clock or on time elapsed? For example, if you execute: sleep 1200 And immediately suspend your system for 10 minutes, will it end in another 10 minutes, or will it continue to wait for the full 20 minutes?

Well I guess it was easy enough to test. After initiating a 5 minute sleep, I suspended the system for about 2 minutes. The answer?

Sleep is calculated using elapsed time of the process, not clock time.


date; sleep 300; date
Tue Jul 2 20:58:41 EDT 2019
Tue Jul 2 21:05:28 EDT 2019


This may have been predictable since man sleep(3) says:

> System activity may lengthen the sleep by an indeterminate amount.

Which kind of implies the amount of time is internal to the sleep process.