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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.12 $ -->
<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.sem-get">
<refnamediv>
<refname>sem_get</refname>
<refpurpose>Get a semaphore id</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>resource</type><methodname>sem_get</methodname>
<methodparam><type>int</type><parameter>key</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>max_acquire</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>perm</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>auto_release</parameter></methodparam>
</methodsynopsis>
<para>
<function>sem_get</function> returns an id that can be used to
access the System V semaphore with the given <parameter>key</parameter>.
</para>
<para>
A second call to <function>sem_get</function> for the same key
will return a different semaphore identifier, but both
identifiers access the same underlying semaphore.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>key</parameter></term>
<listitem>
<para>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>max_acquire</parameter></term>
<listitem>
<para>
The number of processes that can acquire the semaphore simultaneously
is set to <parameter>max_acquire</parameter> (defaults to 1).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>perm</parameter></term>
<listitem>
<para>
The semaphore permissions. Defaults to 0666. Actually this value is
set only if the process finds it is the only process currently
attached to the semaphore.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>auto_release</parameter></term>
<listitem>
<para>
Specifies if the semaphore should be automatically released on request
shutdown.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns a positive semaphore identifier on success, or &false; on
error.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>4.3.0</entry>
<entry>
The <parameter>auto_release</parameter> parameter was added.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>sem_acquire</function></member>
<member><function>sem_release</function></member>
<member><function>ftok</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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