usleep(3C)                     DG/UX R4.11MU05                    usleep(3C)


NAME
       usleep - suspend execution for interval

SYNOPSIS
       usleep(useconds)
       unsigned useconds;

DESCRIPTION
       The current process is suspended from execution for the number of
       microseconds specified by the argument.  The actual suspension time
       may be an arbitrary amount longer because of other activity in the
       system or because of the time spent in processing the call.

       The routine is implemented by setting an interval timer and pausing
       until it occurs.  The previous state of this timer is saved and
       restored.  If the sleep time exceeds the time to the expiration of
       the previous timer, the process sleeps only until the signal would
       have occurred, and the signal is sent a short time later.

       This routine is implemented using setitimer(2); it requires eight
       system calls each time it is invoked.  A similar but less compatible
       function can be obtained with a single select(2); it would not
       restart after signals, but would not interfere with other uses of
       setitimer.


   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |             point     safe  |
                     +---------+-----------------------------+
                     |usleep   |     Y         Y        N    |
                     +---------+-----------------------------+
       In a threaded application, only the thread issuing the usleep call
       suspends for the specified number of seconds. Other threads in the
       process are not affected. A threaded process does not use SIGALRM as
       do non-threaded processes.



SEE ALSO
       alarm(2), getitimer(2), setitimer(2), sigpause(2), reentrant(3),
       sleep(3C).


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