clock_nanosleep

Synopsis

#include <time.h>

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

Status

Implemented

Conformance

IEEE Std 1003.1-2017

Description

If the flag TIMER_ABSTIME is not set in the flags argument, the clock_nanosleep() function shall cause the current thread to be suspended from execution until either the time interval specified by the rqtp argument has elapsed, or a signal is delivered to the calling thread and its action is to invoke a signal-catching function, or the process is terminated. The clock used to measure the time shall be the clock specified by clock_id.

If the flag TIMER_ABSTIME is set in the flags argument, the clock_nanosleep() function shall cause the current thread to be suspended from execution until either the time value of the clock specified by clock_id reaches the absolute time specified by the rqtp argument, or a signal is delivered to the calling thread and its action is to invoke a signal-catching function, or the process is terminated. 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() shall return immediately, and the calling process shall not be suspended.

The suspension time caused by this function may be longer than requested because the argument value is rounded up to an integer multiple of the sleep resolution, or because of the scheduling of other activity by the system. But, except for the case of being interrupted by a signal, the suspension time for the relative clock_nanosleep() function (that is, with the TIMER_ABSTIME flag not set) shall not be less than the time interval specified by rqtp, as measured by the corresponding clock. The suspension for the absolute clock_nanosleep() function (that is, with the TIMER_ABSTIME flag set) shall be in effect at least until the value of the corresponding clock reaches the absolute time specified by rqtp, except for the case of being interrupted by a signal.

The use of the clock_nanosleep() function shall have no effect on the action or blockage of any signal.

The clock_nanosleep() function shall fail if the clock_id argument refers to the CPU-time clock of the calling thread. It is unspecified whether clock_id values of other CPU-time clocks are allowed.

The supported clocks are CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW. For every CPU-time clock (CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID and the clocks returned by clock_getcpuclockid()) clock_nanosleep() fails with ENOTSUP.

Return value

If the clock_nanosleep() function returns because the requested time has elapsed, its return value shall be zero.

If the clock_nanosleep() function returns because it has been interrupted by a signal, it shall return the corresponding error value. For the relative clock_nanosleep() function, if the rmtp argument is non-NULL, the timespec structure referenced by it shall be updated to contain the amount of time remaining in the interval (the requested time minus the time actually slept). The rqtp and rmtp arguments can point to the same object. If the rmtp argument is NULL, the remaining time is not returned. The absolute clock_nanosleep() function has no effect on the structure referenced by rmtp.

If clock_nanosleep() fails, it shall return the corresponding error value.

Errors

The clock_nanosleep() function shall fail if:

  • EINTR - The clock_nanosleep() function was interrupted by a signal.

  • EINVAL - The rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million; or the TIMER_ABSTIME flag was specified in flags and the rqtp argument is outside the range for the clock specified by clock_id; or the clock_id argument does not specify a known clock, or specifies the CPU-time clock of the calling thread.

  • ENOTSUP - The clock_id argument specifies a clock for which clock_nanosleep() is not supported, such as a CPU-time clock.

POSIX deviations

No POSIX deviations discovered.