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<!-- $Revision: 1.14 $ -->
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<refentry id="function.popen">
 <refnamediv>
  <refname>popen</refname>
  <refpurpose>Opens process file pointer</refpurpose>
 </refnamediv>
 <refsect1>
  <title>Description</title>
  <methodsynopsis>
   <type>resource</type><methodname>popen</methodname>
   <methodparam><type>string</type><parameter>command</parameter></methodparam>
   <methodparam><type>string</type><parameter>mode</parameter></methodparam>
  </methodsynopsis>
  <para>
   Opens a pipe to a process executed by forking the command given
   by command.
  </para>
  <para>
   Returns a file pointer identical to that returned by
   <function>fopen</function>, except that it is unidirectional (may
   only be used for reading or writing) and must be closed with
   <function>pclose</function>. This pointer may be used with
   <function>fgets</function>, <function>fgetss</function>, and
   <function>fwrite</function>.
  </para>
  <para>
   If an error occurs, returns &false;.
  </para>
  <note>
   <para>
    If you're looking for bi-directional support (two-way), use
    <function>proc_open</function>.
   </para>
  </note>
  <para>
   <example>
    <title><function>popen</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$handle = popen("/bin/ls", "r");
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   If the command to be executed could not be found, a valid
   resource is returned. This may seem odd, but makes sense; it
   allows you to access any error message returned by the shell:
   <informalexample>
    <programlisting role="php">
<![CDATA[
<?php
error_reporting(E_ALL);

/* Add redirection so we can get stderr. */
$handle = popen('/path/to/spooge 2>&1', 'r');
echo "'$handle'; " . gettype($handle) . "\n";
$read = fread($handle, 2096);
echo $read;
pclose($handle);
?>
]]>
    </programlisting>
   </informalexample>
  </para>
  &note.exec-path;
  &warn.sm.exec;
  <para>
   See also <function>pclose</function>, <function>fopen</function>,
   and <function>proc_open</function>.
  </para>
 </refsect1>
</refentry>

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