394 lines
8.7 KiB
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394 lines
8.7 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of CLOCK_NANOSLEEP</TITLE>
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</HEAD><BODY>
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<H1>CLOCK_NANOSLEEP</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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clock_nanosleep - high-resolution sleep with specifiable clock
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/time.h">time.h</A>></B>
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<PRE>
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<B>int clock_nanosleep(clockid_t </B><I>clock_id</I><B>, int </B><I>flags</I><B>,</B>
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<B> const struct timespec *</B><I>request</I><B>,</B>
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<B> struct timespec *</B><I>remain</I><B>);</B>
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</PRE>
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<P>
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Link with <I>-lrt</I> (only for glibc versions before 2.17).
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>clock_nanosleep</B>():
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<DL COMPACT><DT id="1"><DD>
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_POSIX_C_SOURCE >= 200112L
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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Like
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<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2),
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<B>clock_nanosleep</B>()
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allows the calling thread to sleep for an interval specified
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with nanosecond precision.
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It differs in allowing the caller to select the clock against
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which the sleep interval is to be measured,
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and in allowing the sleep interval to be specified as
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either an absolute or a relative value.
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<P>
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The time values passed to and returned by this call are specified using
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<I>timespec</I>
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structures, defined as follows:
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<P>
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struct timespec {
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<BR> time_t tv_sec; /* seconds */
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<BR> long tv_nsec; /* nanoseconds [0 .. 999999999] */
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};
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<P>
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The
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<I>clock_id</I>
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argument specifies the clock against which the sleep interval
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is to be measured.
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This argument can have one of the following values:
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<DL COMPACT>
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<DT id="2"><B>CLOCK_REALTIME</B>
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<DD>
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A settable system-wide real-time clock.
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<DT id="3"><B>CLOCK_MONOTONIC</B>
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<DD>
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A nonsettable, monotonically increasing clock that measures time
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since some unspecified point in the past that does not change after
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system startup.
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<DT id="4"><B>CLOCK_PROCESS_CPUTIME_ID</B>
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<DD>
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A settable per-process clock that measures CPU time consumed
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by all threads in the process.
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</DL>
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<P>
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See
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<B><A HREF="/cgi-bin/man/man2html?2+clock_getres">clock_getres</A></B>(2)
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for further details on these clocks.
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In addition, the CPU clock IDs returned by
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<B><A HREF="/cgi-bin/man/man2html?3+clock_getcpuclockid">clock_getcpuclockid</A></B>(3)
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and
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<B><A HREF="/cgi-bin/man/man2html?3+pthread_getcpuclockid">pthread_getcpuclockid</A></B>(3)
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can also be passed in
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<I>clock_id</I>.
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<P>
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If
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<I>flags</I>
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is 0, then the value specified in
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<I>request</I>
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is interpreted as an interval relative to the current
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value of the clock specified by
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<I>clock_id</I>.
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<P>
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If
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<I>flags</I>
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is
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<B>TIMER_ABSTIME</B>,
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then
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<I>request</I>
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is interpreted as an absolute time as measured by the clock,
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<I>clock_id</I>.
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If
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<I>request</I>
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is less than or equal to the current value of the clock,
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then
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<B>clock_nanosleep</B>()
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returns immediately without suspending the calling thread.
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<P>
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<B>clock_nanosleep</B>()
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suspends the execution of the calling thread
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until either at least the time specified by
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<I>request</I>
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has elapsed,
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or a signal is delivered that causes a signal handler to be called or
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that terminates the process.
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<P>
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If the call is interrupted by a signal handler,
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<B>clock_nanosleep</B>()
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fails with the error
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<B>EINTR</B>.
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In addition, if
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<I>remain</I>
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is not NULL, and
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<I>flags</I>
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was not
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<B>TIMER_ABSTIME</B>,
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it returns the remaining unslept time in
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<I>remain</I>.
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This value can then be used to call
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<B>clock_nanosleep</B>()
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again and complete a (relative) sleep.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On successfully sleeping for the requested interval,
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<B>clock_nanosleep</B>()
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returns 0.
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If the call is interrupted by a signal handler or encounters an error,
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then it returns one of the positive error number listed in ERRORS.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="5"><B>EFAULT</B>
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<DD>
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<I>request</I>
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or
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<I>remain</I>
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specified an invalid address.
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<DT id="6"><B>EINTR</B>
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<DD>
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The sleep was interrupted by a signal handler; see
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<B><A HREF="/cgi-bin/man/man2html?7+signal">signal</A></B>(7).
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<DT id="7"><B>EINVAL</B>
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<DD>
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The value in the
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<I>tv_nsec</I>
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field was not in the range 0 to 999999999 or
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<I>tv_sec</I>
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was negative.
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<DT id="8"><B>EINVAL</B>
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<DD>
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<I>clock_id</I>
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was invalid.
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(<B>CLOCK_THREAD_CPUTIME_ID</B>
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is not a permitted value for
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<I>clock_id</I>.)
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</DL>
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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The
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<B>clock_nanosleep</B>()
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system call first appeared in Linux 2.6.
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Support is available in glibc since version 2.1.
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008.
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<A NAME="lbAI"> </A>
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<H2>NOTES</H2>
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If the interval specified in
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<I>request</I>
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is not an exact multiple of the granularity underlying clock (see
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<B><A HREF="/cgi-bin/man/man2html?7+time">time</A></B>(7)),
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then the interval will be rounded up to the next multiple.
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Furthermore, after the sleep completes, there may still be a delay before
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the CPU becomes free to once again execute the calling thread.
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<P>
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Using an absolute timer is useful for preventing
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timer drift problems of the type described in
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<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2).
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(Such problems are exacerbated in programs that try to restart
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a relative sleep that is repeatedly interrupted by signals.)
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To perform a relative sleep that avoids these problems, call
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<B><A HREF="/cgi-bin/man/man2html?2+clock_gettime">clock_gettime</A></B>(2)
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for the desired clock,
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add the desired interval to the returned time value,
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and then call
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<B>clock_nanosleep</B>()
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with the
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<B>TIMER_ABSTIME</B>
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flag.
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<P>
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<B>clock_nanosleep</B>()
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is never restarted after being interrupted by a signal handler,
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regardless of the use of the
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<B><A HREF="/cgi-bin/man/man2html?2+sigaction">sigaction</A></B>(2)
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<B>SA_RESTART</B>
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flag.
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<P>
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The
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<I>remain</I>
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argument is unused, and unnecessary, when
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<I>flags</I>
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is
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<B>TIMER_ABSTIME</B>.
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(An absolute sleep can be restarted using the same
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<I>request</I>
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argument.)
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<P>
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POSIX.1 specifies that
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<B>clock_nanosleep</B>()
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has no effect on signals dispositions or the signal mask.
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<P>
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POSIX.1 specifies that after changing the value of the
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<B>CLOCK_REALTIME</B>
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clock via
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<B><A HREF="/cgi-bin/man/man2html?2+clock_settime">clock_settime</A></B>(2),
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the new clock value shall be used to determine the time
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at which a thread blocked on an absolute
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<B>clock_nanosleep</B>()
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will wake up;
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if the new clock value falls past the end of the sleep interval, then the
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<B>clock_nanosleep</B>()
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call will return immediately.
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<P>
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POSIX.1 specifies that
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changing the value of the
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<B>CLOCK_REALTIME</B>
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clock via
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<B><A HREF="/cgi-bin/man/man2html?2+clock_settime">clock_settime</A></B>(2)
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shall have no effect on a thread that is blocked on a relative
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<B>clock_nanosleep</B>().
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<A NAME="lbAJ"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+clock_getres">clock_getres</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+restart_syscall">restart_syscall</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+timer_create">timer_create</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+sleep">sleep</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+usleep">usleep</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?7+time">time</A></B>(7)
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<A NAME="lbAK"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="9"><A HREF="#lbAB">NAME</A><DD>
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<DT id="10"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="11"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="12"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="13"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="14"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="15"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="16"><A HREF="#lbAI">NOTES</A><DD>
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<DT id="17"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="18"><A HREF="#lbAK">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:32 GMT, March 31, 2021
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