php-doc-en/reference/sem/functions/sem-get.xml

<?xml version="1.0" encoding="utf-8"?>
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<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><initializer>1</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>perm</parameter><initializer>0666</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>auto_release</parameter><initializer>1</initializer></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>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>perm</parameter></term>
     <listitem>
      <para>
       The semaphore permissions. 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="notes">
  &reftitle.notes;
  <warning>
   <simpara>
    When using <function>sem_get</function> to access a semaphore created
    outside PHP, note that the semaphore must have been created as a set of 3
    semaphores (for example, by specifying 3 as the <literal>nsems</literal>
    parameter when calling the C <literal>semget()</literal> function),
    otherwise PHP will be unable to access the semaphore.
   </simpara>
  </warning>
 </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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