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

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- splitted from ./en/functions/exec.xml, last change in rev 1.2 -->
<refentry xml:id="function.escapeshellcmd" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>escapeshellcmd</refname>
  <refpurpose>Escape shell metacharacters</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>escapeshellcmd</methodname>
   <methodparam><type>string</type><parameter>command</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>escapeshellcmd</function> escapes any characters in a
   string that might be used to trick a shell command into executing
   arbitrary commands.  This function should be used to make sure
   that any data coming from user input is escaped before this data
   is passed to the <function>exec</function> or
   <function>system</function> functions, or to the <link
   linkend="language.operators.execution">backtick
   operator</link>.
  </para>
  <para>
   Following characters are preceded by a backslash:
   <literal>&amp;#;`|*?~&lt;&gt;^()[]{}$\</literal>, <literal>\x0A</literal>
   and <literal>\xFF</literal>. <literal>'</literal> and <literal>"</literal>
   are escaped only if they are not paired. On Windows, all these characters
   plus <literal>%</literal> and <literal>!</literal> are preceded by a caret
   (<literal>^</literal>).
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>command</parameter></term>
     <listitem>
      <para>
       The command that will be escaped.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The escaped string.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>escapeshellcmd</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// We allow arbitrary number of arguments intentionally here.
$command = './configure '.$_POST['configure_options'];

$escaped_command = escapeshellcmd($command);
 
system($escaped_command);
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
   <warning xmlns="http://docbook.org/ns/docbook">
    <para>
     <function>escapeshellcmd</function> should be used on the whole
     command string, and it still allows the attacker to pass
     arbitrary number of arguments. For escaping a single argument 
     <function>escapeshellarg</function> should be used instead.
    </para>
   </warning>
   <warning xmlns="http://docbook.org/ns/docbook">
    <para>
     Spaces will not be escaped by <function>escapeshellcmd</function>
     which can be problematic on Windows with paths like:
     <literal>C:\Program Files\ProgramName\program.exe</literal>.
     This can be mitigated using the following code snippet:
    <programlisting role="php">
<![CDATA[
<?php
$cmd = preg_replace('`(?<!^) `', '^ ', escapeshellcmd($cmd));
]]>
    </programlisting>
    </para>
   </warning>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>escapeshellarg</function></member>
    <member><function>exec</function></member>
    <member><function>popen</function></member>
    <member><function>system</function></member>
    <member><link linkend="language.operators.execution">backtick operator</link></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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