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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_setattr</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_774"> </a>NAME</h4><blockquote>mq_setattr - set message queue attributes(<b>REALTIME</b>)</blockquote><h4><a name = "tag_000_007_775"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="mqueue.h.html">mqueue.h</a>>int mq_setattr(mqd_t <i>mqdes</i>, const struct mq_attr *<i>mqstat</i>, struct mq_attr *<i>omqstat</i>);</code></pre></blockquote><h4><a name = "tag_000_007_776"> </a>DESCRIPTION</h4><blockquote>The<i>mq_setattr()</i>function is used to set attributes associated withthe open message queue description referenced by the message queue descriptorspecified by<i>mqdes</i>.<p>The message queue attributes corresponding tothe following members defined in the<b>mq_attr</b>structure are set to the specified values uponsuccessful completion of<i>mq_setattr()</i>:<dl compact><dt>mq_flags<dd>The value of this member is the bitwise logical OR of zero or moreof O_NONBLOCK and any implementation-dependent flags.</dl><p>The values of the<i>mq_maxmsg</i>,<i>mq_msgsize</i>and<i>mq_curmsgs</i>members of the<b>mq_attr</b>structure are ignored by<i>mq_setattr()</i>.<p>If<i>omqstat</i>is non-NULL, the function<i>mq_setattr()</i>stores, in the location referenced by<i>omqstat</i>,the previous message queue attributes and the current queue status.These values are the same as would be returned by a call to<i><a href="mq_getattr.html">mq_getattr()</a></i>at that point.</blockquote><h4><a name = "tag_000_007_777"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,the function returns a value of zero andthe attributes of the message queue will have been changed as specified.Otherwise, the message queue attributes are unchanged,and the function returns a value of -1 and sets<i>errno</i>to indicate the error.</blockquote><h4><a name = "tag_000_007_778"> </a>ERRORS</h4><blockquote>The <i>mq_setattr()</i>function will fail if:<dl compact><dt>[EBADF]<dd>The<i>mqdes</i>argument is not a valid message queue descriptor.<dt>[ENOSYS]<dd>The function<i>mq_setattr()</i>is not supported by this implementation.</dl></blockquote><h4><a name = "tag_000_007_779"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_780"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_781"> </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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