usleep(3) — Linux manual page

usleep(3)               Library Functions Manual               usleep(3)

NAME

       usleep - suspend execution for microsecond intervals

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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

DESCRIPTION

       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

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

ERRORS

       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

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ usleep()                            │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       None.

HISTORY

       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.

CAVEATS

       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

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

COLOPHON

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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)

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