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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | CAVEATS | SEE ALSO | COLOPHON |
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usleep(3) Library Functions Manual usleep(3)
usleep - suspend execution for microsecond intervals
Standard C library (libc, -lc)
#include <unistd.h>
int usleep(useconds_t usec);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
usleep():
Since glibc 2.12:
(_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE
Before glibc 2.12:
_BSD_SOURCE || _XOPEN_SOURCE >= 500
The usleep() function suspends execution of the calling thread for
(at least) usec microseconds. The sleep may be lengthened
slightly by any system activity or by the time spent processing
the call or by the granularity of system timers.
The usleep() function returns 0 on success. On error, -1 is
returned, with errno set to indicate the error.
EINTR Interrupted by a signal; see signal(7).
EINVAL usec is greater than or equal to 1000000. (On systems
where that is considered an error.)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ usleep() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
None.
4.3BSD, POSIX.1-2001. POSIX.1-2001 declares it obsolete,
suggesting nanosleep(2) instead. Removed in POSIX.1-2008.
On the original BSD implementation, and before glibc 2.2.2, the
return type of this function is void. The POSIX version returns
int, and this is also the prototype used since glibc 2.2.2.
Only the EINVAL error return is documented by SUSv2 and
POSIX.1-2001.
The interaction of this function with the SIGALRM signal, and with
other timer functions such as alarm(2), sleep(3), nanosleep(2),
setitimer(2), timer_create(2), timer_delete(2),
timer_getoverrun(2), timer_gettime(2), timer_settime(2), ualarm(3)
is unspecified.
alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
sleep(3), ualarm(3), useconds_t(3type), time(7)
This page is part of the man-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 is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 usleep(3)
Pages that refer to this page: free(1), gawk(1), clock_nanosleep(2), getitimer(2), nanosleep(2), select(2), __ppc_get_timebase(3), time_t(3type), ualarm(3), signal(7), time(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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