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<html><head><title>IPC::Semaphore (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_135.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_137.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.136. IPC::Semaphore</h2><p><a name="INDEX-1488" />System V Semaphore IPC object class.Uses constants defined in IPC::SysV.</p><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>new</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em> = new IPC::Semaphore(<em class="replaceable">key</em>, <em class="replaceable">nsems</em>, <em class="replaceable">flags</em>)</pre><p>Creates a new semaphore set associated with<em class="replaceable"><tt>key</tt></em> and containing<em class="replaceable"><tt>nsems</tt></em> semaphores. Uses<em class="replaceable"><tt>flags</tt></em> to set the permissions. Creates thenew set if the following are true:</p><ul><li><p><em class="replaceable"><tt>key</tt></em> is equal to IPC_PRIVATE.</p></li><li><p><em class="replaceable"><tt>key</tt></em> doesn't already havean associated semaphore identifier, and <tt class="literal">FLAGS &IPC_CREAT</tt> is true.</p></li></ul></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>getall</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->getall</pre><p>Returns the values of the semaphore set as an array.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>getncnt</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->getncnt(<em class="replaceable">sem</em>)</pre><p>Returns the number of processes waiting for the semaphore<em class="replaceable"><tt>sem</tt></em> to become greater than its currentvalue.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>getpid</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->getpid(<em class="replaceable">sem</em>)</pre><p>Returns the process ID of the last process that operated on semaphore<em class="replaceable"><tt>sem</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>getval</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->getval(<em class="replaceable">sem</em>)</pre><p>Returns the current value of semaphore <em class="replaceable">sem</em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>getzcnt</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->getzcnt(<em class="replaceable">sem</em>)</pre><p>Returns the number of processes waiting for the semaphore<em class="replaceable"><tt>sem</tt></em> to become <tt class="literal">0</tt>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>id</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->id</pre><p>Returns the system identifier for the semaphore set.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>op</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->op(<em class="replaceable">oplist</em>)</pre><p>Passes a list of operations to the <tt class="literal">semop</tt> function.<em class="replaceable"><tt>oplist</tt></em> is the list of operations,consisting of a concatenation of smaller lists. Each of the smallerlists has three values: the semaphore number, the operation, and aflag. See the <tt class="literal">semop</tt> function in <a href="ch05_01.htm">Chapter 5, "Function Reference"</a> for more information.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>remove</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->remove</pre><p>Removes and destroys the semaphore set.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>set</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><table width="515" border="0" cellpadding="5"><tr><td align="left"><pre>$<em class="replaceable">sem</em>->set(<em class="replaceable">stat</em>$<em class="replaceable">sem</em>->set(<em class="replaceable">name</em>=><em class="replaceable">value</em>[, <em class="replaceable">name</em>=><em class="replaceable">value</em>...])</pre></td><td align="right" /></tr></table><p><p>Accepts either a stat object as returned by the<tt class="literal">stat</tt> method or a list of name/value pairs and setsthe following values of the stat structure associated with thesemaphore set:</p><blockquote><pre class="code">uidgidmode (the permission bits)</pre></blockquote></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>setall</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->setall(<em class="replaceable">values</em>)</pre><p>Sets the values of all the semaphores in the set to those given bythe <em class="replaceable"><tt>values</tt></em> list. The number of values onthe list must match the number of semaphores in the set.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>setval</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">sem</em>->setval(<em class="replaceable">n</em>, <em class="replaceable">value</em>)</pre><p>Sets the <em class="replaceable">n</em>th value in the semaphore set to<em class="replaceable"><tt>value</tt></em>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>stat</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">ds</em> = $<em class="replaceable">sem</em>->stat</pre><p>Returns an object of type <tt class="literal">IPC::Semaphore::stat</tt>(which is a subclass of Class::Struct) that provides the followingfields:</p><blockquote><pre class="code">uid gid cuid cgidmode ctime otime nsems</pre></blockquote></div><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_135.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_137.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.135. IPC::Open3</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.137. IPC::SysV</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. 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