SLEEP(3) BSD Library Functions Manual SLEEP(3)
NAME
sleep — suspend thread execution for an interval measured in seconds
LIBRARY
Standard C Library (libc, −lc)
SYNOPSIS
#include <unistd.h>
unsigned int
sleep(unsigned int seconds);
DESCRIPTION
The sleep() function suspends execution of the calling thread until either seconds seconds have elapsed or a signal is delivered to the thread and its action is to invoke a signal-catching function or to terminate the thread or process. System activity may lengthen the sleep by an indeterminate amount.
This function is implemented using nanosleep(2) by pausing for seconds seconds or until a signal occurs. Consequently, in this implementation, sleeping has no effect on the state of process timers, and there is no special handling for SIGALRM.
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 requested time minus the time actually slept) in seconds.
SEE ALSO
nanosleep(2), usleep(3)
STANDARDS
The sleep() function conforms to ISO/IEC 9945-1:1990 (‘‘POSIX.1’’).
HISTORY
A sleep() function appeared in Version 7 AT&T UNIX.
BSD February 13, 1998 BSD