clock_nanosleep(2) - Linux manual page (original) (raw)
clocknanosleep(2) System Calls Manual clocknanosleep(2)
NAME top
clock_nanosleep - high-resolution sleep with specifiable clockLIBRARY top
Standard C library (_libc_, _-lc_), since glibc 2.17
Before glibc 2.17, Real-time library (_librt_, _-lrt_)SYNOPSIS top
**#include <time.h>**
**int clock_nanosleep(clockid_t** _clockid_**, int** _flags_**,**
**const struct timespec ***_t_**,**
**struct timespec *_Nullable** _remain_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**clock_nanosleep**():
_POSIX_C_SOURCE >= 200112LDESCRIPTION top
Like [nanosleep(2)](../man2/nanosleep.2.html), **clock_nanosleep**() allows the calling thread to
sleep for an interval specified with nanosecond precision. It
differs in allowing the caller to select the clock against which
the sleep interval is to be measured, and in allowing the sleep
interval to be specified as either an absolute or a relative
value.
The time values passed to and returned by this call are specified
using **timespec**(3) structures.
The _clockid_ argument specifies the clock against which the sleep
interval is to be measured. This argument can have one of the
following values:
**CLOCK_REALTIME**
A settable system-wide real-time clock.
**CLOCK_TAI** (since Linux 3.10)
A system-wide clock derived from wall-clock time but
counting leap seconds.
**CLOCK_MONOTONIC**
A nonsettable, monotonically increasing clock that
measures time since some unspecified point in the past
that does not change after system startup.
**CLOCK_BOOTTIME** (since Linux 2.6.39)
Identical to **CLOCK_MONOTONIC**, except that it also includes
any time that the system is suspended.
**CLOCK_PROCESS_CPUTIME_ID**
A settable per-process clock that measures CPU time
consumed by all threads in the process.
See [clock_getres(2)](../man2/clock%5Fgetres.2.html) for further details on these clocks. In
addition, the CPU clock IDs returned by [clock_getcpuclockid(3)](../man3/clock%5Fgetcpuclockid.3.html)
and [pthread_getcpuclockid(3)](../man3/pthread%5Fgetcpuclockid.3.html) can also be passed in _clockid_.
If _flags_ is 0, then the value specified in _t_ is interpreted as an
interval relative to the current value of the clock specified by
_clockid_.
If _flags_ is **TIMER_ABSTIME**, then _t_ is interpreted as an absolute
time as measured by the clock, _clockid_. If _t_ is less than or
equal to the current value of the clock, then **clock_nanosleep**()
returns immediately without suspending the calling thread.
**clock_nanosleep**() suspends the execution of the calling thread
until either at least the time specified by _t_ has elapsed, or a
signal is delivered that causes a signal handler to be called or
that terminates the process.
If the call is interrupted by a signal handler, **clock_nanosleep**()
fails with the error **EINTR**. In addition, if _remain_ is not NULL,
and _flags_ was not **TIMER_ABSTIME**, it returns the remaining unslept
time in _remain_. This value can then be used to call
**clock_nanosleep**() again and complete a (relative) sleep.RETURN VALUE top
On successfully sleeping for the requested interval,
**clock_nanosleep**() returns 0. If the call is interrupted by a
signal handler or encounters an error, then it returns one of the
positive error number listed in ERRORS.ERRORS top
**EFAULT** _t_ or _remain_ specified an invalid address.
**EINTR** The sleep was interrupted by a signal handler; see
[signal(7)](../man7/signal.7.html).
**EINVAL** The value in the _tvnsec_ field was not in the range [0,
999999999] or _tvsec_ was negative.
**EINVAL** _clockid_ was invalid. (**CLOCK_THREAD_CPUTIME_ID** is not a
permitted value for _clockid_.)
**ENOTSUP**
The kernel does not support sleeping against this _clockid_.STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001. Linux 2.6, glibc 2.1.NOTES top
If the interval specified in _t_ is not an exact multiple of the
granularity underlying clock (see [time(7)](../man7/time.7.html)), then the interval
will be rounded up to the next multiple. Furthermore, after the
sleep completes, there may still be a delay before the CPU
becomes free to once again execute the calling thread.
Using an absolute timer is useful for preventing timer drift
problems of the type described in [nanosleep(2)](../man2/nanosleep.2.html). (Such problems
are exacerbated in programs that try to restart a relative sleep
that is repeatedly interrupted by signals.) To perform a
relative sleep that avoids these problems, call [clock_gettime(2)](../man2/clock%5Fgettime.2.html)
for the desired clock, add the desired interval to the returned
time value, and then call **clock_nanosleep**() with the
**TIMER_ABSTIME** flag.
**clock_nanosleep**() is never restarted after being interrupted by a
signal handler, regardless of the use of the [sigaction(2)](../man2/sigaction.2.html)
**SA_RESTART** flag.
The _remain_ argument is unused, and unnecessary, when _flags_ is
**TIMER_ABSTIME**. (An absolute sleep can be restarted using the
same _t_ argument.)
POSIX.1 specifies that **clock_nanosleep**() has no effect on signals
dispositions or the signal mask.
POSIX.1 specifies that after changing the value of the
**CLOCK_REALTIME** clock via [clock_settime(2)](../man2/clock%5Fsettime.2.html), the new clock value
shall be used to determine the time at which a thread blocked on
an absolute **clock_nanosleep**() will wake up; if the new clock
value falls past the end of the sleep interval, then the
**clock_nanosleep**() call will return immediately.
POSIX.1 specifies that changing the value of the **CLOCK_REALTIME**
clock via [clock_settime(2)](../man2/clock%5Fsettime.2.html) shall have no effect on a thread that
is blocked on a relative **clock_nanosleep**().SEE ALSO top
[clock_getres(2)](../man2/clock%5Fgetres.2.html), [nanosleep(2)](../man2/nanosleep.2.html), [restart_syscall(2)](../man2/restart%5Fsyscall.2.html),
[timer_create(2)](../man2/timer%5Fcreate.2.html), [sleep(3)](../man3/sleep.3.html), **timespec**(3), [usleep(3)](../man3/usleep.3.html), [time(7)](../man7/time.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.9.1 2024-05-02 clocknanosleep(2)
Pages that refer to this page:nanosleep(2), PR_SET_TIMERSLACK(2const), restart_syscall(2), syscalls(2), clockid_t(3type), timespec(3type), signal(7), time(7), time_namespaces(7)