php-doc-en/reference/exec/functions/system.xml

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  <refentry id="function.system">
   <refnamediv>
    <refname>system</refname>
    <refpurpose>Execute an external program and display the output</refpurpose>
   </refnamediv>
   <refsect1>
    &reftitle.description;
     <methodsynopsis>
      <type>string</type><methodname>system</methodname>
      <methodparam><type>string</type><parameter>command</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter role="reference">return_var</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>system</function> is just like the C version of the
     function in that it executes the given
     <parameter>command</parameter> and outputs the result.  If a
     variable is provided as the second argument, then the return
     status code of the executed command will be written to this
     variable.
    </para>
    &warn.escapeshell;
    &note.exec-bg;
    <para>
     The <function>system</function> call also tries to automatically
     flush the web server's output buffer after each line of output if
     PHP is running as a server module.
    </para>
    <para>
     Returns the last line of the command output on success, and &false;
     on failure.
    </para>
    <para>
     If you need to execute a command and have all the data from the
     command passed directly back without any interference, use the
     <function>passthru</function> function.
    </para>
    <para>
     <example>
      <title><function>system</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php
echo '<pre>';

// Outputs all the result of shellcommand "ls", and returns
// the last output line into $last_line. Stores the return value
// of the shell command in $retval.
$last_line = system('ls', $retval);

// Printing additional info
echo '
</pre>
<hr />Last line of the output: ' . $last_line . '
<hr />Return value: ' . $retval;
?>
]]>
      </programlisting>
     </example>
    </para>
    &note.exec-path;
    &warn.sm.exec;
    <para>
     See also <function>exec</function>,
     <function>passthru</function>, <function>popen</function>,
     <function>escapeshellcmd</function>,
     <function>pcntl_exec</function>, and the <link
     linkend="language.operators.execution">backtick operator</link>.
    </para>
   </refsect1>
  </refentry>

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