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sleep

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

sleep - sleep for a specified number of seconds

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <unistd.h>
unsigned int sleep(unsigned int seconds);

DESCRIPTION

sleep() causes the calling thread to sleep either until the number of rea-time seconds specified in seconds have elapsed or until a signal arrives which is not ignored.

RETURN VALUE

Zero if the requested time has elapsed, or the number of seconds left to sleep, if the call was interrupted by a signal handler.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
sleep()	Thread safety	M-Unsafe sig:SIGCHLD/linux

VERSIONS

On Linux, sleep() is implemented via nanosleep(2). See the nanosleep(2) man page for a discussion of the clock used. On some systems, sleep() may be implemented using alarm(2) and SIGALRM (POSIX.1 permits this); mixing calls to alarm(2) and sleep() is a bad idea.

STANDARDS

POSIX.-2008.

HISTORY

POSIX.-2001.

CAVEATS

Using longjmp(3) from a signal handler or modifying the handling of SIGALRM while sleeping will cause undefined results.