142 lines
5.1 KiB
HTML
142 lines
5.1 KiB
HTML
<!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 The Open Group, All Rights Reserved -->
|
|
<title>sem_getvalue</title>
|
|
</head>
|
|
<body bgcolor="white">
|
|
<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
|
|
</script>
|
|
|
|
<basefont size="3"> <a name="sem_getvalue"></a> <a name="tag_03_630"></a><!-- sem_getvalue -->
|
|
<!--header start-->
|
|
<center><font size="2">The Open Group Base Specifications Issue 6<br>
|
|
IEEE Std 1003.1-2001<br>
|
|
Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
|
|
|
|
<!--header end-->
|
|
<hr size="2" noshade>
|
|
<h4><a name="tag_03_630_01"></a>NAME</h4>
|
|
|
|
<blockquote>sem_getvalue - get the value of a semaphore (<b>REALTIME</b>)</blockquote>
|
|
|
|
<h4><a name="tag_03_630_02"></a>SYNOPSIS</h4>
|
|
|
|
<blockquote class="synopsis">
|
|
<div class="box"><code><tt><sup>[<a href="javascript:open_code('SEM')">SEM</a>]</sup> <img src="../images/opt-start.gif" alt=
|
|
"[Option Start]" border="0"> #include <<a href="../basedefs/semaphore.h.html">semaphore.h</a>><br>
|
|
<br>
|
|
int sem_getvalue(sem_t *restrict</tt> <i>sem</i><tt>, int *restrict</tt> <i>sval</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_630_03"></a>DESCRIPTION</h4>
|
|
|
|
<blockquote>
|
|
<p>The <i>sem_getvalue</i>() function shall update the location referenced by the <i>sval</i> argument to have the value of the
|
|
semaphore referenced by <i>sem</i> without affecting the state of the semaphore. The updated value represents an actual semaphore
|
|
value that occurred at some unspecified time during the call, but it need not be the actual value of the semaphore when it is
|
|
returned to the calling process.</p>
|
|
|
|
<p>If <i>sem</i> is locked, then the value returned by <i>sem_getvalue</i>() is either zero or a negative number whose absolute
|
|
value represents the number of processes waiting for the semaphore at some unspecified time during the call.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_04"></a>RETURN VALUE</h4>
|
|
|
|
<blockquote>
|
|
<p>Upon successful completion, the <i>sem_getvalue</i>() function shall return a value of zero. Otherwise, it shall return a value
|
|
of -1 and set <i>errno</i> to indicate the error.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_05"></a>ERRORS</h4>
|
|
|
|
<blockquote>
|
|
<p>The <i>sem_getvalue</i>() function shall fail if:</p>
|
|
|
|
<dl compact>
|
|
<dt>[EINVAL]</dt>
|
|
|
|
<dd>The <i>sem</i> argument does not refer to a valid semaphore.</dd>
|
|
</dl>
|
|
</blockquote>
|
|
|
|
<hr>
|
|
<div class="box"><em>The following sections are informative.</em></div>
|
|
|
|
<h4><a name="tag_03_630_06"></a>EXAMPLES</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_07"></a>APPLICATION USAGE</h4>
|
|
|
|
<blockquote>
|
|
<p>The <i>sem_getvalue</i>() function is part of the Semaphores option and need not be available on all implementations.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_08"></a>RATIONALE</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_09"></a>FUTURE DIRECTIONS</h4>
|
|
|
|
<blockquote>
|
|
<p>None.</p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_10"></a>SEE ALSO</h4>
|
|
|
|
<blockquote>
|
|
<p><a href="semctl.html"><i>semctl</i>()</a> , <a href="semget.html"><i>semget</i>()</a> , <a href="semop.html"><i>semop</i>()</a>
|
|
, <a href="sem_post.html"><i>sem_post</i>()</a> , <a href="sem_timedwait.html"><i>sem_timedwait</i>()</a> , <a href=
|
|
"sem_trywait.html"><i>sem_trywait</i>()</a> , <a href="sem_wait.html"><i>sem_wait</i>()</a> , the Base Definitions volume of
|
|
IEEE Std 1003.1-2001, <a href="../basedefs/semaphore.h.html"><i><semaphore.h></i></a></p>
|
|
</blockquote>
|
|
|
|
<h4><a name="tag_03_630_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_630_12"></a>Issue 6</h4>
|
|
|
|
<blockquote>
|
|
<p>The <i>sem_getvalue</i>() function is marked as part of the Semaphores option.</p>
|
|
|
|
<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Semaphores
|
|
option.</p>
|
|
|
|
<p>The <a href="../functions/sem_timedwait.html"><i>sem_timedwait</i>()</a> function is added to the SEE ALSO section for alignment
|
|
with IEEE Std 1003.1d-1999.</p>
|
|
|
|
<p>The <b>restrict</b> keyword is added to the <i>sem_getvalue</i>() prototype for alignment with the ISO/IEC 9899:1999
|
|
standard.</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>
|
|
|