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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>mq_getattr</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="mq_getattr"></a> <a name="tag_03_383"></a><!-- mq_getattr --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_383_01"></a>NAME</h4><blockquote>mq_getattr - get message queue attributes (<b>REALTIME</b>)</blockquote><h4><a name="tag_03_383_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('MSG')">MSG</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/mqueue.h.html">mqueue.h</a>><br><br> int mq_getattr(mqd_t</tt> <i>mqdes</i><tt>, struct mq_attr *</tt><i>mqstat</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_383_03"></a>DESCRIPTION</h4><blockquote><p>The <i>mq_getattr</i>() function shall obtain status information and attributes of the message queue and the open message queuedescription associated with the message queue descriptor.</p><p>The <i>mqdes</i> argument specifies a message queue descriptor.</p><p>The results shall be returned in the <b>mq_attr</b> structure referenced by the <i>mqstat</i> argument.</p><p>Upon return, the following members shall have the values associated with the open message queue description as set when themessage queue was opened and as modified by subsequent <a href="../functions/mq_setattr.html"><i>mq_setattr</i>()</a> calls:<i>mq_flags</i>.</p><p>The following attributes of the message queue shall be returned as set at message queue creation: <i>mq_maxmsg</i>,<i>mq_msgsize</i>.</p><p>Upon return, the following members within the <b>mq_attr</b> structure referenced by the <i>mqstat</i> argument shall be set tothe current state of the message queue:</p><dl compact><dt><i>mq_curmsgs</i></dt><dd>The number of messages currently on the queue.</dd></dl></blockquote><h4><a name="tag_03_383_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, the <i>mq_getattr</i>() function shall return zero. Otherwise, the function shall return -1 and set<i>errno</i> to indicate the error.</p></blockquote><h4><a name="tag_03_383_05"></a>ERRORS</h4><blockquote><p>The <i>mq_getattr</i>() function shall fail if:</p><dl compact><dt>[EBADF]</dt><dd>The <i>mqdes</i> argument is not a valid message queue descriptor.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_383_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_383_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_383_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_383_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_383_10"></a>SEE ALSO</h4><blockquote><p><a href="mq_open.html"><i>mq_open</i>()</a> , <a href="mq_send.html"><i>mq_send</i>()</a> , <a href="mq_setattr.html"><i>mq_setattr</i>()</a> , <a href="mq_timedsend.html"><i>mq_timedsend</i>()</a> , <a href="msgctl.html"><i>msgctl</i>()</a> , <a href="msgget.html"><i>msgget</i>()</a> , <a href="msgrcv.html"><i>msgrcv</i>()</a> , <ahref="msgsnd.html"><i>msgsnd</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/mqueue.h.html"><i><mqueue.h></i></a></p></blockquote><h4><a name="tag_03_383_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p></blockquote><h4><a name="tag_03_383_12"></a>Issue 6</h4><blockquote><p>The <i>mq_getattr</i>() function is marked as part of the Message Passing option.</p><p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the MessagePassing option.</p><p>The <a href="../functions/mq_timedsend.html"><i>mq_timedsend</i>()</a> function is added to the SEE ALSO section for alignmentwith IEEE Std 1003.1d-1999.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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