NANOSLEEP(2)

NAME
nanosleep, clock_nanosleep - high resolution sleep

LIBRARY
libc

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 delivered 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 p1003.1b-93. The clock_nanosleep() function conforms to p1003.1-2008.

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 architectures. This means that a request to sleep for less than 10ms (1 / HZ seconds), is rounded up to that.