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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
   Multithreading (see pthreads(7))
       The usleep() function is thread-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 3.55 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/.

					    2013-12-10					USLEEP(3)
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