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:
               _BSD_SOURCE ||
                   (_XOPEN_SOURCE >= 500 ||
                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
                   !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

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 not smaller than 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 4.04 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
       http://www.kernel.org/doc/man-pages/.

                                  2015-03-02                         USLEEP(3)
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