USLEEP(3)                 OpenBSD Programmer's Manual                USLEEP(3)

NAME
     usleep - suspend execution for interval of microseconds



SYNOPSIS
     #include <unistd.h>

     int
     usleep(useconds_t microseconds);

DESCRIPTION
     The usleep() function suspends execution of the calling process for
     microseconds microseconds of time.  System activity or time spent in pro-
     cessing the call may lengthen the sleep slightly.

     This routine is implemented using nanosleep(2);  it requires one system
     call each time it is invoked.  A similar but less compatible function can
     be obtained with a single select(2);  such a function would not restart
     after signals, and also does not interfere with other uses of
     setitimer(2) (not that usleep() interferes with interval timers anymore).

RETURN VALUES
     If the usleep() function returns because the requested time has elapsed,
     the value returned will be zero.

     If the usleep() function returns due to the delivery of a signal, the
     value returned will be the -1, and the global variable errno will be set
     to indicate the interruption.

ERRORS
     If any of the following conditions occur, the usleep() function shall re-
     turn -1 and set errno to the corresponding value.

     [EINTR]       usleep() was interrupted by the delivery of a signal.

     [EINVAL]      useconds specified a value of 1,000,000 or more microsec-
                   onds.

NOTES
     A microsecond is 0.000001 seconds.

SEE ALSO
     getitimer(2),  nanosleep(2),  setitimer(2),  alarm(3),  sigpause(3),
     sleep(3),  ualarm(3)

STANDARDS
     The usleep() function conforms to X/Open Portability Guide Issue 4.2
     (``XPG4.2'').

HISTORY
     The usleep() function appeared in 4.3BSD.

OpenBSD 2.6                    November 4, 1997                              1