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NAME

       usleep - suspend execution for microsecond intervals

SYNOPSIS

       /* BSD version */
       #include <unistd.h>

       void usleep(unsigned long usec);

       /* SUSv2 version */
       #define _XOPEN_SOURCE 500
       #include <unistd.h>

       int usleep(useconds_t usec);

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

       None (BSD). Or: 0 on success, -1 on error (SUSv2).

ERRORS

       EINTR  Interrupted by a signal.

       EINVAL usec is not smaller than 1000000.  (On  systems  where  that  is
              considered an error.)

CONFORMING TO

       4.3BSD.   The SUSv2 version returns int, and this is also the prototype
       used by glibc 2.2.2.  Only the EINVAL error  return  is  documented  by
       SUSv2.

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);

       This  type is defined by <sys/types.h> included by <unistd.h> but glibc
       defines it only when _XOPEN_SOURCE has a value not less  than  500,  or
       both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined.

       The  interaction  of  this  function  with the SIGALRM signal, and with
       other  timer  functions  such   as   alarm(),   sleep(),   nanosleep(),
       setitimer(),    timer_create(),   timer_delete(),   timer_getoverrun(),
       timer_gettime(), timer_settime(), ualarm() is unspecified.

       This function is obsolete. Use nanosleep(2) or setitimer(2) instead.

SEE ALSO

       alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2), sleep(3)

                                  2003-07-23                         USLEEP(3)