usleep(3) — Linux manual page


USLEEP(3)               Linux Programmer's Manual              USLEEP(3)

NAME         top

       usleep - suspend execution for microsecond intervals

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 since 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 │

CONFORMING TO         top

       4.3BSD, POSIX.1-2001.  POSIX.1-2001 declares this function
       obsolete; use nanosleep(2) instead.  POSIX.1-2008 removes the
       specification of usleep().

       On the original BSD implementation, and in glibc before version
       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

NOTES         top

       The type useconds_t is an unsigned integer type capable of
       holding integers in the range [0,1000000].  Programs will be more
       portable if they never mention this type explicitly.  Use

           #include <unistd.h>
               unsigned int usecs;

       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), time(7)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

                               2021-03-22                      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)ualarm(3)signal(7)time(7)