sleep(5) - phpMan

clock_nanosleep (2)  - high-resolution sleep with specifiable clock
clock_nanosleep (3p) - high resolution sleep with specifiable clock (ADVANCED...
nanosleep (2)        - high-resolution sleep
nanosleep (3p)       - high resolution sleep (REALTIME)
rtcwake (8)          - enter a system sleep state until specified wakeup time
sleep (1)            - delay for a specified amount of time
sleep (1p)           - suspend execution for an interval
sleep (3)            - sleep for the specified number of seconds
sleep (3p)           - suspend execution for an interval of time
sleep.conf.d (5)     - Suspend and hibernation configuration file
systemd-hibernate.service (8) - System sleep state logic
systemd-hybrid-sleep.service (8) - System sleep state logic
systemd-sleep (8)    - System sleep state logic
systemd-sleep.conf (5) - Suspend and hibernation configuration file
systemd-suspend.service (8) - System sleep state logic
Time::HiRes (3pm)    - High resolution alarm, sleep, gettimeofday, interval t...
usleep (1)           - sleep some number of microseconds
usleep (3)           - suspend execution for microsecond intervals
usleep (3p)          - suspend execution for an interval