usleep(3) — Linux manual page


usleep(3)               Library Functions Manual               usleep(3)

NAME         top

       usleep - suspend execution for microsecond intervals

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <unistd.h>

       int usleep(useconds_t usec);

   Feature Test Macro Requirements for glibc (see

           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

DESCRIPTION         top

       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.

RETURN VALUE         top

       The usleep() function returns 0 on success.  On error, -1 is
       returned, with errno set to indicate the error.

ERRORS         top

       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.)

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ usleep()                            │ Thread safety │ MT-Safe │

STANDARDS         top


HISTORY         top

       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

CAVEATS         top

       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.

SEE ALSO         top

       alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
       sleep(3), ualarm(3), useconds_t(3type), time(7)

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                      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)