288 lines
6.7 KiB
HTML
288 lines
6.7 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 MQ_SEND</TITLE>
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</HEAD><BODY>
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<H1>MQ_SEND</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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mq_send, mq_timedsend - send a message to a message queue
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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/mqueue.h">mqueue.h</A>></B>
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<B>int mq_send(mqd_t </B><I>mqdes</I><B>, const char *</B><I>msg_ptr</I><B>,</B>
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<B> size_t </B><I>msg_len</I><B>, unsigned int </B><I>msg_prio</I><B>);</B>
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<B>#include <<A HREF="file:///usr/include/time.h">time.h</A>></B>
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<B>#include <<A HREF="file:///usr/include/mqueue.h">mqueue.h</A>></B>
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<B>int mq_timedsend(mqd_t </B><I>mqdes</I><B>, const char *</B><I>msg_ptr</I><B>,</B>
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<B> size_t </B><I>msg_len</I><B>, unsigned int </B><I>msg_prio</I><B>,</B>
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<B> const struct timespec *</B><I>abs_timeout</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>mq_timedsend</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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<B>mq_send</B>()
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adds the message pointed to by
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<I>msg_ptr</I>
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to the message queue referred to by the message queue descriptor
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<I>mqdes</I>.
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The
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<I>msg_len</I>
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argument specifies the length of the message pointed to by
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<I>msg_ptr</I>;
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this length must be less than or equal to the queue's
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<I>mq_msgsize</I>
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attribute.
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Zero-length messages are allowed.
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<P>
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The
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<I>msg_prio</I>
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argument is a nonnegative integer that specifies the priority
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of this message.
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Messages are placed on the queue in decreasing order of priority,
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with newer messages of the same priority being placed after
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older messages with the same priority.
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See
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<B><A HREF="/cgi-bin/man/man2html?7+mq_overview">mq_overview</A></B>(7)
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for details on the range for the message priority.
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<P>
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If the message queue is already full
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(i.e., the number of messages on the queue equals the queue's
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<I>mq_maxmsg</I>
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attribute), then, by default,
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<B>mq_send</B>()
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blocks until sufficient space becomes available to allow the message
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to be queued, or until the call is interrupted by a signal handler.
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If the
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<B>O_NONBLOCK</B>
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flag is enabled for the message queue description,
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then the call instead fails immediately with the error
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<B>EAGAIN</B>.
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<P>
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<B>mq_timedsend</B>()
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behaves just like
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<B>mq_send</B>(),
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except that if the queue is full and the
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<B>O_NONBLOCK</B>
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flag is not enabled for the message queue description, then
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<I>abs_timeout</I>
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points to a structure which specifies how long the call will block.
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This value is an absolute timeout in seconds and nanoseconds
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since the Epoch, 1970-01-01 00:00:00 +0000 (UTC),
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specified in the following structure:
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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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If the message queue is full,
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and the timeout has already expired by the time of the call,
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<B>mq_timedsend</B>()
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returns immediately.
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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>mq_send</B>()
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and
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<B>mq_timedsend</B>()
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return zero; on error, -1 is returned, with
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<I>errno</I>
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set to indicate the error.
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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="2"><B>EAGAIN</B>
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<DD>
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The queue was full, and the
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<B>O_NONBLOCK</B>
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flag was set for the message queue description referred to by
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<I>mqdes</I>.
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<DT id="3"><B>EBADF</B>
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<DD>
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The descriptor specified in
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<I>mqdes</I>
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was invalid or not opened for writing.
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<DT id="4"><B>EINTR</B>
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<DD>
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The call 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="5"><B>EINVAL</B>
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<DD>
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The call would have blocked, and
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<I>abs_timeout</I>
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was invalid, either because
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<I>tv_sec</I>
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was less than zero, or because
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<I>tv_nsec</I>
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was less than zero or greater than 1000 million.
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<DT id="6"><B>EMSGSIZE</B>
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<DD>
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<I>msg_len</I>
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was greater than the
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<I>mq_msgsize</I>
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attribute of the message queue.
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<DT id="7"><B>ETIMEDOUT</B>
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<DD>
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The call timed out before a message could be transferred.
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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>mq_send</B>(),
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<B>mq_timedsend</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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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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On Linux,
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<B>mq_timedsend</B>()
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is a system call, and
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<B>mq_send</B>()
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is a library function layered on top of that system call.
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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?3+mq_close">mq_close</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mq_getattr">mq_getattr</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mq_notify">mq_notify</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mq_open">mq_open</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mq_receive">mq_receive</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mq_unlink">mq_unlink</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?7+mq_overview">mq_overview</A></B>(7),
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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="8"><A HREF="#lbAB">NAME</A><DD>
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<DT id="9"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="10"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="11"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="12"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="13"><A HREF="#lbAG">ATTRIBUTES</A><DD>
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<DT id="14"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="15"><A HREF="#lbAI">NOTES</A><DD>
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<DT id="16"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="17"><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: 00:05:48 GMT, March 31, 2021
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