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(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       The  usleep()  function  suspends  execution  of  the calling process 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
       0 on success, -1 on 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.)

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 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                                           2007-07-26                                                  USLEEP(3)