usleep

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



NAME
       usleep - suspend execution for microsecond intervals

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 since 2.19: */ _DEFAULT_SOURCE
                   || /* Glibc versions <= 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 cause of 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 │
       └──────────┴───────────────┴─────────┘
CONFORMING TO
       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 POSIX.1-2001.

NOTES
       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;
           ...
               usleep(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
       alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
       sleep(3), ualarm(3), time(7)

COLOPHON
       This page is part of release 5.02 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
       https://www.kernel.org/doc/man-pages/.



                                  2017-09-15                         USLEEP(3)