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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>mq_notify</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_742"> </a>NAME</h4><blockquote>mq_notify - notify process that a message is available(<b>REALTIME</b>)</blockquote><h4><a name = "tag_000_007_743"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="mqueue.h.html">mqueue.h</a>>int mq_notify(mqd_t <i>mqdes</i>, const struct sigevent *<i>notification</i>);</code></pre></blockquote><h4><a name = "tag_000_007_744"> </a>DESCRIPTION</h4><blockquote>If the argument<i>notification</i>is not NULL,this function registers the calling process to be notifiedof message arrival at an empty message queueassociated with the specified message queue descriptor,<i>mqdes</i>.The notification specified by the<i>notification</i>argument will be sent to the processwhen the message queue transitions from empty to non-empty.At any time,only one process may be registered for notification by a message queue.If the calling process or any other process has already registeredfor notification of message arrival at the specified message queue,subsequent attempts to register for that message queue fail.<p>If<i>notification</i>is NULL and the process is currently registered for notificationby the specified message queue,the existing registration is removed.<p>When the notification is sent to the registered process,its registration will be removed.The message queue will then be available for registration.<p>If a process has registered for notification of message arrivalat a message queue and some thread is blocked in<i><a href="mq_receive.html">mq_receive()</a></i>waiting to receive a message when a message arrives at the queue,the arriving message satisfies the appropriate<i><a href="mq_receive.html">mq_receive()</a></i>.The resultingbehaviour is as if the message queue remains empty,and no notification is sent.</blockquote><h4><a name = "tag_000_007_745"> </a>RETURN VALUE</h4><blockquote>Upon successful completion, the<i>mq_notify()</i>function returns a value of zero;otherwise, the function returns a value of -1 and sets<i>errno</i>to indicate the error.</blockquote><h4><a name = "tag_000_007_746"> </a>ERRORS</h4><blockquote>The <i>mq_notify()</i>function will fail if:<dl compact><dt>[EBADF]<dd>The<i>mqdes</i>argument is not a valid message queue descriptor.<dt>[EBUSY]<dd>A process is already registered for notification by the message queue.<dt>[ENOSYS]<dd>The function<i>mq_notify()</i>is not supported by this implementation.</dl></blockquote><h4><a name = "tag_000_007_747"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_748"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_749"> </a>SEE ALSO</h4><blockquote><i><a href="mq_open.html">mq_open()</a></i>,<i><a href="mq_send.html">mq_send()</a></i>,<i><a href="mqueue.h.html"><mqueue.h></a></i>,<i><a href="msgctl.html">msgctl()</a></i>,<i><a href="msgget.html">msgget()</a></i>,<i><a href="msgrcv.html">msgrcv()</a></i>,<i><a href="msgsnd.html">msgsnd()</a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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