clock_getres.3: Re-create as link to new location of clock_getres page

[thirdparty/man-pages.git] / man2 / clock_nanosleep.2

.\" Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH CLOCK_NANOSLEEP 2 2008-07-09 "Linux" "Linux Programmer's Manual"
.SH NAME
clock_nanosleep \- high-resolution sleep with specifiable clock
.SH SYNOPSIS
.B #include <time.h>
.nf
.sp
.BI "int clock_nanosleep(clockid_t " clock_id ", int " flags ,
.BI "                    const struct timespec *" request ,
.BI "                    struct timespec *" remain );
.fi
.sp
Link with \fI\-lrt\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR clock_nanosleep ():
_XOPEN_SOURCE\ >=\ 600
.SH DESCRIPTION
Like
.BR nanosleep (2),
.BR clock_nanosleep ()
allows the caller 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
.I timespec
structures, defined as follows:
.sp
.in +4n
.nf
struct timespec {
    time_t tv_sec;        /* seconds */
    long   tv_nsec;       /* nanoseconds [0 .. 999999999] */
};
.fi
.in

The
.I clock_id
argument specifies the clock against which the sleep interval
is to be measured.
This argument can have one of the following values:
.TP 17
.BR CLOCK_REALTIME
A settable system-wide real-time clock.
.TP
.BR CLOCK_MONOTONIC
A non-settable, monotonically increasing clock that measures time
since some unspecified point in the past that does not change after
system startup.
.\" On Linux this clock measures time since boot.
.TP
.BR CLOCK_PROCESS_CPUTIME_ID
A settable per-process clock that measures CPU time consumed
by all threads in the process.
.\" There is some trickery between glibc and the kernel
.\" to deal with the CLOCK_PROCESS_CPUTIME_ID case.
.PP
See
.BR clock_getres (3)
for further details on these clocks.

If
.I flags
is 0, then the value specified in
.I request
is interpreted as an interval relative to the current
value of the clock specified by
.IR clock_id .

If
.I flags
is
.BR TIMER_ABSTIME ,
then
.I request
is interpreted as an absolute time as measured by the clock,
.IR clock_id .
If
.I request
is less than or equal to the current value of the clock,
then
.BR clock_nanosleep ()
returns immediately without suspending the calling thread.

.BR clock_nanosleep ()
suspends the execution of the calling thread
until either at least the time specified by
.IR request
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,
.BR clock_nanosleep ()
returns \-1, and sets
.I errno
to
.BR EINTR .
In addition, if
.I remain
is not NULL, and
.I flags
was not
.BR TIMER_ABSTIME ,
it returns the remaining unslept time in
.IR remain .
This value can then be used to call
.BR clock_nanosleep ()
again and complete a (relative) sleep.
.SH "RETURN VALUE"
On successfully sleeping for the requested interval,
.BR clock_nanosleep ()
returns 0.
If the call is interrupted by a signal handler or encounters an error,
then it returns a positive error number.
.SH ERRORS