153 lines
5.7 KiB
HTML
153 lines
5.7 KiB
HTML
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<title>mq_notify</title>
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<basefont size="3"> <a name="mq_notify"></a> <a name="tag_03_384"></a><!-- mq_notify -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_384_01"></a>NAME</h4>
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<blockquote>mq_notify - notify process that a message is available (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_03_384_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('MSG')">MSG</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/mqueue.h.html">mqueue.h</a>><br>
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<br>
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int mq_notify(mqd_t</tt> <i>mqdes</i><tt>, const struct sigevent *</tt><i>notification</i><tt>); <img src="../images/opt-end.gif"
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alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_384_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>If the argument <i>notification</i> is not NULL, this function shall register the calling process to be notified of message
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arrival at an empty message queue associated with the specified message queue descriptor, <i>mqdes</i>. The notification specified
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by the <i>notification</i> argument shall be sent to the process when the message queue transitions from empty to non-empty. At any
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time, only one process may be registered for notification by a message queue. If the calling process or any other process has
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already registered for notification of message arrival at the specified message queue, subsequent attempts to register for that
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message queue shall fail.</p>
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<p>If <i>notification</i> is NULL and the process is currently registered for notification by the specified message queue, the
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existing registration shall be removed.</p>
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<p>When the notification is sent to the registered process, its registration shall be removed. The message queue shall then be
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available for registration.</p>
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<p>If a process has registered for notification of message arrival at a message queue and some thread is blocked in <a href=
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"../functions/mq_receive.html"><i>mq_receive</i>()</a> waiting to receive a message when a message arrives at the queue, the
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arriving message shall satisfy the appropriate <a href="../functions/mq_receive.html"><i>mq_receive</i>()</a>. The resulting
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behavior is as if the message queue remains empty, and no notification shall be sent.</p>
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</blockquote>
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<h4><a name="tag_03_384_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, the <i>mq_notify</i>() function shall return a value of zero; otherwise, the function shall return a
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value of -1 and set <i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_384_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>mq_notify</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EBADF]</dt>
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<dd>The <i>mqdes</i> argument is not a valid message queue descriptor.</dd>
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<dt>[EBUSY]</dt>
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<dd>A process is already registered for notification by the message queue.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_384_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_384_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_384_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_384_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_384_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="mq_open.html"><i>mq_open</i>()</a> , <a href="mq_send.html"><i>mq_send</i>()</a> , <a href=
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"mq_timedsend.html"><i>mq_timedsend</i>()</a> , <a href="msgctl.html"><i>msgctl</i>()</a> , <a href=
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"msgget.html"><i>msgget</i>()</a> , <a href="msgrcv.html"><i>msgrcv</i>()</a> , <a href="msgsnd.html"><i>msgsnd</i>()</a> , the
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Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/mqueue.h.html"><i><mqueue.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_384_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
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</blockquote>
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<h4><a name="tag_03_384_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>mq_notify</i>() function is marked as part of the Message Passing option.</p>
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<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Message
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Passing option.</p>
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<p>The <a href="../functions/mq_timedsend.html"><i>mq_timedsend</i>()</a> function is added to the SEE ALSO section for alignment
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with IEEE Std 1003.1d-1999.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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