SLEEP(S) UNIX System V SLEEP(S)
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 less than that requested for two
reasons: (1) Because scheduled wakeups occur at fixed 1-
second intervals, (on the second, according to an internal
clock) and (2) because any caught signal will terminate the
sleep following execution of that signal's catching routine.
Also, the suspension time may be longer than requested by an
arbitrary amount due to the scheduling of other activity in
the system. The value returned by sleep will be the
``unslept'' amount (the requested time minus the time
actually slept) in case the caller had an alarm set to go
off earlier than the end of the requested sleep time, or
premature arousal due to another caught signal.
The routine is implemented by setting an alarm signal and
pausing until it (or some other signal) occurs. The
previous state of the alarm signal is saved and restored.
The calling program may have set up an alarm signal before
calling sleep. If the sleep time exceeds the time till such
alarm signal, the process sleeps only until the alarm signal
would have occurred. The caller's alarm catch routine is
executed just before the sleep routine returns. But if the
sleep time is less than the time till such alarm, the prior
alarm time is reset to go off at the same time it would have
without the intervening sleep.
See Also
alarm(S), pause(S), signal(S)
Standards Conformance
sleep is conformant with:
AT&T SVID Issue 2, Select Code 307-127;
The X/Open Portability Guide II of January 1987;
IEEE POSIX Std 1003.1-1988 with C Standard Language-
Dependent System Support;
and NIST FIPS 151-1.
(printed 6/20/89)