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sleep(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ATTRIBUTES \|VERSIONS \|STANDARDS \|HISTORY \|CAVEATS \|SEE ALSO \|COLOPHON

sleep(3)                 Library Functions Manualsleep(3)

NAME top

       sleep - sleep for a specified number of seconds

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

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

DESCRIPTION top

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

RETURN VALUE top

       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 top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────┬───────────────┬─────────────────────────────┐       │Interface│Attribute│Value│       ├──────────────────┼───────────────┼─────────────────────────────┤       │sleep()          │ Thread safety │ MT-Unsafe sig:SIGCHLD/linux │       └──────────────────┴───────────────┴─────────────────────────────┘

VERSIONS top

       On Linux,sleep() is implemented viananosleep(2).  See thenanosleep(2) man page for a discussion of the clock used.       On some systems,sleep() may be implemented usingalarm(2) andSIGALRM(POSIX.1 permits this); mixing calls toalarm(2) andsleep() is a bad idea.

STANDARDS top

       POSIX.1-2008.

HISTORY top

       POSIX.1-2001.

CAVEATS top

       Usinglongjmp(3) from a signal handler or modifying the handling       ofSIGALRMwhile sleeping will cause undefined results.

COLOPHON top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17sleep(3)

Pages that refer to this page:sleep(1), alarm(2), clock_nanosleep(2), getitimer(2), nanosleep(2), ualarm(3), usleep(3), signal(7), signal-safety(7), time(7)