NAME

     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 time interval specified by the rqtp
     argument has elapsed, 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 clock used to measure
     the time is specified by the clock_id argument.

     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 by the
     clock_id argument reaches the absolute time specified by the rqtp argument, or a signal is
     delivered to the calling process and its action is to invoke a signal-catching function or
     to terminate the process.  If, at the time of the call, the time value specified by rqtp is
     less than or equal to the time value of the specified clock, then clock_nanosleep() returns
     immediately and the calling thread is not suspended.

     The suspension time may be longer than requested due to the scheduling of other activity by
     the system.  An unmasked signal will terminate the sleep early, regardless of the SA_RESTART
     value on the interrupting signal.  The rqtp and rmtp arguments can point to the same object.

     The following clock_id values are supported:

           CLOCK_MONOTONIC
           CLOCK_MONOTONIC_FAST
           CLOCK_MONOTONIC_PRECISE
           CLOCK_REALTIME
           CLOCK_REALTIME_FAST
           CLOCK_REALTIME_PRECISE
           CLOCK_SECOND
           CLOCK_UPTIME
           CLOCK_UPTIME_FAST
           CLOCK_UPTIME_PRECISE

     The nanosleep() function behaves like clock_nanosleep() with a clock_id argument of
     CLOCK_REALTIME and without the TIMER_ABSTIME flag in the flags argument.

RETURN VALUES

     These functions return zero when the requested time has elapsed.

     If these functions return for any other reason, then clock_nanosleep() will directly return
     the error number, and nanosleep() will return -1 with the global variable errno set to
     indicate the error.  If a relative sleep is interrupted by a signal and rmtp is non-NULL,
     the timespec structure it references is updated to contain the unslept amount (the request
     time minus the time actually slept).

ERRORS

     These functions can fail with the following errors.

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

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

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

     [EINVAL]           The flags argument contained an invalid flag.

     [EINVAL]           The clock_id argument was CLOCK_THREAD_CPUTIME_ID or an unrecognized
                        value.

     [ENOTSUP]          The clock_id argument was valid but not supported by this implementation
                        of clock_nanosleep().

SEE ALSO

     clock_gettime(2), sigaction(2), sleep(3)

STANDARDS

     These functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).