usleep(2)                                                         usleep(2)




 NAME    [Toc]    [Back]
      usleep - suspend execution for an interval

 SYNOPSIS    [Toc]    [Back]
      #include <unistd.h>

      int usleep(useconds_t useconds);

 DESCRIPTION    [Toc]    [Back]
      The usleep() function will cause the calling thread to be suspended
      from execution until either the number of real-time microseconds
      specified by the argument useconds has elapsed, or a signal is
      delivered to the calling thread and its action is to invoke a
      signal-catching function or to terminate the process.

      The suspension time may be longer than requested due to the scheduling
      of other activities by the system, or because of the time spent in
      processing the call.

      The useconds argument must be less than 1,000,000.  If the value of
      useconds is 0, then the call has no effect.

      If a SIGALRM signal is generated for the calling process during
      execution of usleep() and if the SIGALRM signal is being ignored or
      blocked from delivery, it is unspecified whether usleep() returns when
      the SIGALRM signal is scheduled; if the signal is being blocked, it is
      also unspecified whether it remains pending after usleep() returns or
      it is discarded.

      If a SIGALRM signal is generated for the calling process during
      execution of usleep(), except as a result of a prior call to alarm(),
      and if the SIGALRM signal is not being ignored or blocked from
      delivery, it is unspecified whether that signal has any effect other
      than causing usleep() to return.

      If a signal-catching function interrupts usleep() and examines or
      changes either the time a SIGALRM is scheduled to be generated, the
      action associated with the SIGALRM signal, or whether the SIGALRM
      signal is blocked from delivery, the results are unspecified.

      If a signal-catching function interrupts usleep() and calls
      siglongjmp() or longjmp() to restore an environment saved prior to the
      usleep() call, the action associated with the SIGALRM signal and the
      time at which a SIGALRM signal is scheduled to be generated are
      unspecified, it is also unspecified whether the SIGALRM signal is
      blocked, unless the process's signal mask is restored as part of the
      environment.

      Implementations may place limitations on the granularity of timer
      values. For each interval timer, if the requested timer value requires
      a finer granularity than the implementation supports, the actual timer



 Hewlett-Packard Company            - 1 -   HP-UX 11i Version 2: August 2003






 usleep(2)                                                         usleep(2)




      value will be rounded up to the next supported value.

      Interactions between usleep() and any of the following are
      unspecified: nanosleep(), setitimer(), timer_create(), timer_delete(),
      timer_getoverrun(), timer_gettime(), timer_settime(), ualarm(),
      sleep().

 RETURN VALUE    [Toc]    [Back]
      On successful completion, usleep() returns 0. Otherwise, it returns -1
      and sets errno to indicate the error.

 ERRORS    [Toc]    [Back]
      The usleep() function may fail if:

           [EINVAL]                 The time interval specified 1,000,000 or
                                    more microseconds.

 APPLICATION USAGE    [Toc]    [Back]
      The usleep() function is included for its historical usage. The
      setitimer() function is preferred over this function. Multi-threaded
      applications are recommended to use nanosleep() instead of usleep().
      usleep() is also a thread canceling point.

 SEE ALSO    [Toc]    [Back]
      alarm(2), getitimer(2), nanosleep(2), sigaction(2), sleep(3C),
      timer_create(2), timer_delete(2), timer_getoverrun(2),
      timer_gettime(2), timer_settime(2), <unistd.h>.

 CHANGE HISTORY    [Toc]    [Back]
      First released in Issue 4, Version 2.


 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003