nanosleep(2) - NetBSD Manual Pages

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NANOSLEEP(2)              NetBSD System Calls Manual              NANOSLEEP(2)


NAME

     nanosleep, clock_nanosleep -- high resolution sleep


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <time.h>

     int
     clock_nanosleep(clockid_t clock_id, int flags,
         const struct timespec *rqtp, struct timespec *rmtp);

     int
     nanosleep(const struct timespec *rqtp, struct timespec *rmtp);


DESCRIPTION

     If the TIMER_ABSTIME flag is not set in the flags argument, then
     clock_nanosleep() suspends execution of the calling thread until either
     the number of seconds and nanoseconds specified in the rqtp argument have
     elapsed using the clock in the clock_id argument, or a signal is deliv-
     ered to the calling process and its action is to invoke a signal catching
     function or to terminate the process.

     If the TIMER_ABSTIME flag is set in the flags argument, then
     clock_nanosleep() suspends execution of the calling thread until either
     the value of the clock specified in the clock_id argument reaches the
     value of the rqtp argument in seconds and nanoseconds, or a signal is
     delivered to the calling process 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 activity by the system.

     The nanosleep() function behaves like clock_nanosleep() with the clock_id
     argument equal to CLOCK_MONOTONIC and the flags argument having
     TIMER_ABSTIME not set.

     The struct timespec is described in timespec(3).  The clock_id specified
     is the time source, which is described in clock_gettime(2).


RETURN VALUES

     If the clock_nanosleep() or the nanosleep() functions return because the
     requested time has elapsed, the value returned will be zero.

     If the clock_nanosleep() or the nanosleep() functions return due to the
     delivery of a signal, then clock_nanosleep() will return directly the
     error number, and nanosleep() will return -1, and the global variable
     errno will be set to indicate the interruption.  If rmtp is non-NULL, the
     timespec structure it references is updated to contain the unslept amount
     (the request time minus the time actually slept), unless it is called
     from clock_nanosleep() with a flags argument of TIMER_ABSTIME.  In that
     case, the rmtp argument is left unmodified.


ERRORS

     If any of the following conditions occur, the nanosleep() function shall
     return -1 and set errno to the corresponding value, and the
     clock_nanosleep() function shall return the error number directly.

     [EFAULT]           Either rqtp or rmtp points to memory that is not a
                        valid part of the process address space.

     [EINTR]            nanosleep was interrupted by the delivery of a signal.

     [EINVAL]           rqtp specified a nanosecond value less than zero or
                        greater than 1000 million.

     [ENOSYS]           nanosleep is not supported by this implementation.

     [ENOTSUP]          for clock_nanosleep(), the clock specified in the
                        clock_id argument is not supported.


SEE ALSO

     clock_gettime(2), sleep(3), timespec(3)


STANDARDS

     The nanosleep() function conforms to IEEE Std 1003.1b-1993 (``POSIX.1'').
     The clock_nanosleep() function conforms to IEEE Std 1003.1-2008
     (``POSIX.1'').


BUGS

     The NetBSD kernel is not tickless, so the maximum sleep resolution is
     determined by the value of HZ which is by default 100 in most architec-
     tures.  This means that a request to sleep for less than 10ms (1 / HZ
     seconds), is rounded up to that.

NetBSD 9.4                     November 11, 2016                    NetBSD 9.4