155 lines
5.3 KiB
HTML
155 lines
5.3 KiB
HTML
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<title>mq_getattr</title>
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<basefont size="3"> <a name="mq_getattr"></a> <a name="tag_03_383"></a><!-- mq_getattr -->
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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_383_01"></a>NAME</h4>
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<blockquote>mq_getattr - get message queue attributes (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_03_383_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_getattr(mqd_t</tt> <i>mqdes</i><tt>, struct mq_attr *</tt><i>mqstat</i><tt>); <img src="../images/opt-end.gif" alt=
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"[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_383_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>mq_getattr</i>() function shall obtain status information and attributes of the message queue and the open message queue
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description associated with the message queue descriptor.</p>
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<p>The <i>mqdes</i> argument specifies a message queue descriptor.</p>
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<p>The results shall be returned in the <b>mq_attr</b> structure referenced by the <i>mqstat</i> argument.</p>
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<p>Upon return, the following members shall have the values associated with the open message queue description as set when the
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message queue was opened and as modified by subsequent <a href="../functions/mq_setattr.html"><i>mq_setattr</i>()</a> calls:
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<i>mq_flags</i>.</p>
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<p>The following attributes of the message queue shall be returned as set at message queue creation: <i>mq_maxmsg</i>,
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<i>mq_msgsize</i>.</p>
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<p>Upon return, the following members within the <b>mq_attr</b> structure referenced by the <i>mqstat</i> argument shall be set to
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the current state of the message queue:</p>
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<dl compact>
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<dt><i>mq_curmsgs</i></dt>
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<dd>The number of messages currently on the queue.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_03_383_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, the <i>mq_getattr</i>() function shall return zero. Otherwise, the function shall return -1 and set
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<i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_383_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>mq_getattr</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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</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_383_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_383_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_383_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_383_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_383_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_setattr.html"><i>mq_setattr</i>()</a> , <a href="mq_timedsend.html"><i>mq_timedsend</i>()</a> , <a href=
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"msgctl.html"><i>msgctl</i>()</a> , <a href="msgget.html"><i>msgget</i>()</a> , <a href="msgrcv.html"><i>msgrcv</i>()</a> , <a
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href="msgsnd.html"><i>msgsnd</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/mqueue.h.html"><i><mqueue.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_383_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_383_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>mq_getattr</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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