NAME
sleep —
suspend process execution for interval
of seconds
SYNOPSIS
#include
<unistd.h>
unsigned int
sleep(unsigned
int seconds);
DESCRIPTION
The
sleep()
function suspends execution of the calling process until either the number
of seconds specified by seconds have elapsed or a
signal is delivered to the calling process and its action is to invoke a
signal-catching function or to terminate the process. The suspension time
may be longer than requested due to the scheduling of other activity by the
system.
This function is implemented using
nanosleep(2); it requires one system call each time it is invoked. A
similar but less compatible function can be obtained with a single
select(2); such a function would not restart after signals, and also
does not interfere with other uses of
setitimer(2) (not that
sleep()
interferes with interval timers anymore).
RETURN VALUES
If the sleep() function returns because
the requested time has elapsed, the value returned will be zero. If the
sleep() function returns due to the delivery of a
signal, the value returned will be the unslept amount (the request time
minus the time actually slept) in seconds.
SEE ALSO
sleep(1), nanosleep(2), select(2), setitimer(2), sigaction(2), sigsuspend(2), alarm(3), pause(3), usleep(3)
STANDARDS
The sleep() function conforms to
IEEE Std 1003.1-1990 (“POSIX.1”).
HISTORY
A sleep() function appeared in
Version 7 AT&T UNIX.