ultrix man page for sleep

sleep(3)						     Library Functions Manual							  sleep(3)

Name
       sleep - suspend execution for interval

Syntax
       unsigned
       sleep(seconds)
       unsigned seconds;

Description
       The  current process is suspended from execution for the number of seconds specified by the argument.  The actual suspension time may be up
       to 1 second less than that requested, because scheduled wakeups occur at fixed 1-second intervals, and an arbitrary amount  longer  because
       of other activity in the system.

       The  routine  is  implemented  by  setting  an  interval  timer and pausing until it occurs.  The previous state of this timer is saved and
       restored.  If the sleep time exceeds the time to the expiration of the previous timer, the process sleeps only until the signal would  have
       occurred, and the signal is sent 1 second later.

Return Values
       The  value  returned by is the unslept amount(the requested time minus the time actually slept). This return value may be non-zero in cases
       where the caller had an alarm set to go off earlier than the end of the requested time, or where was interrupted due to a caught signal(see
       ENVIRONMENT below).

Environment
       POSIX
       SYSTEM_FIVE
       When  your  program  is compiled in POSIX or System V mode, the will be terminated by any caught signal. The function will return following
       execution of the signal's catching routine.

See Also
       setitimer(2), sigpause(2)

																	  sleep(3)