250 lines
5.8 KiB
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250 lines
5.8 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 UALARM</TITLE>
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</HEAD><BODY>
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<H1>UALARM</H1>
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Section: Linux Programmer's Manual (3)<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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ualarm - schedule signal after given number of microseconds
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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/unistd.h">unistd.h</A>></B>
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<B>useconds_t ualarm(useconds_t </B><I>usecs</I><B>, useconds_t </B><I>interval</I><B>);</B>
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</PRE>
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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>ualarm</B>():
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<DL COMPACT><DT id="1"><DD>
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<DL COMPACT>
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<DT id="2">Since glibc 2.12:<DD>
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<PRE>
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(_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
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|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
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|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
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<DT id="3"></PRE>
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<DD>
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Before glibc 2.12:
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_BSD_SOURCE || _XOPEN_SOURCE >= 500
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</DL>
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The
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<B>ualarm</B>()
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function causes the signal
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<B>SIGALRM</B>
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to be sent to the invoking process after (not less than)
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<I>usecs</I>
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microseconds.
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The delay may be lengthened slightly by any system activity
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or by the time spent processing the call or by the
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granularity of system timers.
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<P>
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Unless caught or ignored, the
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<B>SIGALRM</B>
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signal will terminate the process.
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<P>
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If the
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<I>interval</I>
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argument is nonzero, further
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<B>SIGALRM</B>
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signals will be sent every
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<I>interval</I>
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microseconds after the first.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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This function returns the number of microseconds remaining for
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any alarm that was previously set, or 0 if no alarm was pending.
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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="4"><B>EINTR</B>
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<DD>
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Interrupted by a signal; see
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<B><A HREF="/cgi-bin/man/man2html?7+signal">signal</A></B>(7).
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<DT id="5"><B>EINVAL</B>
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<DD>
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<I>usecs</I> or <I>interval</I> is not smaller than 1000000.
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(On systems where that is considered an error.)
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</DL>
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<A NAME="lbAG"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>ualarm</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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4.3BSD, POSIX.1-2001.
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POSIX.1-2001 marks
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<B>ualarm</B>()
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as obsolete.
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POSIX.1-2008 removes the specification of
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<B>ualarm</B>().
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4.3BSD, SUSv2, and POSIX do not define any errors.
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<A NAME="lbAI"> </A>
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<H2>NOTES</H2>
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POSIX.1-2001 does not specify what happens if the
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<I>usecs</I>
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argument is 0.
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On Linux (and probably most other systems),
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the effect is to cancel any pending alarm.
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<P>
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The type
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<I>useconds_t</I>
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is an unsigned integer type capable of holding integers
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in the range [0,1000000].
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On the original BSD implementation, and in glibc before version 2.1,
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the arguments to
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<B>ualarm</B>()
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were instead typed as
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<I>unsigned int</I>.
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Programs will be more portable if they never mention
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<I>useconds_t</I>
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explicitly.
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<P>
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The interaction of this function with
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other timer functions such as
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<B><A HREF="/cgi-bin/man/man2html?2+alarm">alarm</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?2+nanosleep">nanosleep</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setitimer">setitimer</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?2+timer_delete">timer_delete</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?2+timer_gettime">timer_gettime</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+timer_settime">timer_settime</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+usleep">usleep</A></B>(3)
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is unspecified.
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<P>
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This function is obsolete.
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Use
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<B><A HREF="/cgi-bin/man/man2html?2+setitimer">setitimer</A></B>(2)
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or POSIX interval timers
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(<B><A HREF="/cgi-bin/man/man2html?2+timer_create">timer_create</A></B>(2),
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etc.)
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instead.
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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+alarm">alarm</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+getitimer">getitimer</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+select">select</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setitimer">setitimer</A></B>(2),
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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="6"><A HREF="#lbAB">NAME</A><DD>
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<DT id="7"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="8"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="9"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="10"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="11"><A HREF="#lbAG">ATTRIBUTES</A><DD>
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<DT id="12"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="13"><A HREF="#lbAI">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="15"><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: 00:05:59 GMT, March 31, 2021
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</BODY>
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