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.)

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 3.54 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/.

                                                   2013-04-19                                          USLEEP(3)