322 lines
7.4 KiB
HTML
322 lines
7.4 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 TIMER_SETTIME</TITLE>
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</HEAD><BODY>
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<H1>TIMER_SETTIME</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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timer_settime, timer_gettime - arm/disarm and fetch
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state of POSIX per-process timer
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/time.h">time.h</A>></B>
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<B>int timer_settime(timer_t </B><I>timerid</I><B>, int </B><I>flags</I><B>,</B>
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<B> const struct itimerspec *</B><I>new_value</I><B>,</B>
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<B> struct itimerspec *</B><I>old_value</I><B>);</B>
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<B>int timer_gettime(timer_t </B><I>timerid</I><B>, struct itimerspec *</B><I>curr_value</I><B>);</B>
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</PRE>
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<P>
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Link with <I>-lrt</I>.
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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>timer_settime</B>(),
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<B>timer_gettime</B>():
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_POSIX_C_SOURCE >= 199309L
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>timer_settime</B>()
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arms or disarms the timer identified by
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<I>timerid</I>.
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The
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<I>new_value</I>
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argument is pointer to an
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<I>itimerspec</I>
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structure that specifies the new initial value and
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the new interval for the timer.
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The
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<I>itimerspec</I>
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structure is 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 */
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};
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<P>
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struct itimerspec {
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<BR> struct timespec it_interval; /* Timer interval */
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<BR> struct timespec it_value; /* Initial expiration */
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};
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<P>
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Each of the substructures of the
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<I>itimerspec</I>
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structure is a
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<I>timespec</I>
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structure that allows a time value to be specified
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in seconds and nanoseconds.
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These time values are measured according to the clock
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that was specified when the timer was created by
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<B><A HREF="/cgi-bin/man/man2html?2+timer_create">timer_create</A></B>(2).
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<P>
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If
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<I>new_value->it_value</I>
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specifies a nonzero value (i.e., either subfield is nonzero), then
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<B>timer_settime</B>()
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arms (starts) the timer,
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setting it to initially expire at the given time.
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(If the timer was already armed,
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then the previous settings are overwritten.)
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If
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<I>new_value->it_value</I>
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specifies a zero value
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(i.e., both subfields are zero),
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then the timer is disarmed.
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<P>
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The
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<I>new_value->it_interval</I>
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field specifies the period of the timer, in seconds and nanoseconds.
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If this field is nonzero, then each time that an armed timer expires,
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the timer is reloaded from the value specified in
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<I>new_value->it_interval</I>.
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If
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<I>new_value->it_interval</I>
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specifies a zero value,
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then the timer expires just once, at the time specified by
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<I>it_value</I>.
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<P>
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By default, the initial expiration time specified in
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<I>new_value->it_value</I>
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is interpreted relative to the current time on the timer's
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clock at the time of the call.
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This can be modified by specifying
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<B>TIMER_ABSTIME</B>
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in
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<I>flags</I>,
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in which case
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<I>new_value->it_value</I>
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is interpreted as an absolute value as measured on the timer's clock;
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that is, the timer will expire when the clock value reaches the
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value specified by
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<I>new_value->it_value</I>.
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If the specified absolute time has already passed,
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then the timer expires immediately,
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and the overrun count (see
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<B><A HREF="/cgi-bin/man/man2html?2+timer_getoverrun">timer_getoverrun</A></B>(2))
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will be set correctly.
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<P>
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If the value of the
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<B>CLOCK_REALTIME</B>
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clock is adjusted while an absolute timer based on that clock is armed,
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then the expiration of the timer will be appropriately adjusted.
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Adjustments to the
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<B>CLOCK_REALTIME</B>
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clock have no effect on relative timers based on that clock.
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<P>
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If
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<I>old_value</I>
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is not NULL, then it points to a buffer
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that is used to return the previous interval of the timer (in
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<I>old_value->it_interval</I>)
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and the amount of time until the timer
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would previously have next expired (in
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<I>old_value->it_value</I>).
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<P>
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<B>timer_gettime</B>()
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returns the time until next expiration, and the interval,
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for the timer specified by
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<I>timerid</I>,
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in the buffer pointed to by
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<I>curr_value</I>.
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The time remaining until the next timer expiration is returned in
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<I>curr_value->it_value</I>;
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this is always a relative value, regardless of whether the
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<B>TIMER_ABSTIME</B>
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flag was used when arming the timer.
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If the value returned in
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<I>curr_value->it_value</I>
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is zero, then the timer is currently disarmed.
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The timer interval is returned in
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<I>curr_value->it_interval</I>.
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If the value returned in
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<I>curr_value->it_interval</I>
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is zero, then this is a "one-shot" timer.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success,
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<B>timer_settime</B>()
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and
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<B>timer_gettime</B>()
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return 0.
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On error, -1 is returned, and
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<I>errno</I>
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is set to indicate the error.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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These functions may fail with the following errors:
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<DL COMPACT>
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<DT id="1"><B>EFAULT</B>
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<DD>
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<I>new_value</I>,
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<I>old_value</I>,
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or
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<I>curr_value</I>
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is not a valid pointer.
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<DT id="2"><B>EINVAL</B>
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<DD>
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<I>timerid</I>
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is invalid.
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</DL>
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<P>
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<B>timer_settime</B>()
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may fail with the following errors:
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<DL COMPACT>
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<DT id="3"><B>EINVAL</B>
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<DD>
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<I>new_value.it_value</I>
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is negative; or
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<I>new_value.it_value.tv_nsec</I>
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is negative or greater than 999,999,999.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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These system calls are available since Linux 2.6.
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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>EXAMPLE</H2>
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See
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<B><A HREF="/cgi-bin/man/man2html?2+timer_create">timer_create</A></B>(2).
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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+timer_create">timer_create</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+timer_getoverrun">timer_getoverrun</A></B>(2),
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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="4"><A HREF="#lbAB">NAME</A><DD>
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<DT id="5"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="6"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="7"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="8"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="9"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="10"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="11"><A HREF="#lbAI">EXAMPLE</A><DD>
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<DT id="12"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="13"><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: 00:05:35 GMT, March 31, 2021
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</BODY>
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</HTML>
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