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)

Linux man-pages 6.7               2023-10-31                         usleep(3)