php-doc-en/reference/filesystem/functions/realpath.xml

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<refentry xml:id="function.realpath" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>realpath</refname>
  <refpurpose>Returns canonicalized absolute pathname</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>string</type><type>false</type></type><methodname>realpath</methodname>
   <methodparam><type>string</type><parameter>path</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>realpath</function> expands all symbolic links and
   resolves references to <literal>/./</literal>, <literal>/../</literal> and extra <literal>/</literal> characters in
   the input <parameter>path</parameter> and returns the canonicalized
   absolute pathname.  
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>path</parameter></term>
     <listitem>
      <para>
       The path being checked.
       <note>
        <para>
         Whilst a path must be supplied, the value can be an empty string.
         In this case, the value is interpreted as the current directory.
        </para>
       </note>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the canonicalized absolute pathname on success. The resulting path 
   will have no symbolic link, <literal>/./</literal> or <literal>/../</literal> components. Trailing delimiters,
   such as <literal>\</literal> and <literal>/</literal>, are also removed.
  </para>
  <para>
   <function>realpath</function> returns &false; on failure, e.g. if
   the file does not exist.
  </para>
  <note>
   <para>
    The running script must have executable permissions on all directories in
    the hierarchy, otherwise <function>realpath</function> will return
    &false;.
   </para>
  </note>
  <note>
   <para>
    For case-insensitive filesystems <function>realpath</function> may or may
    not normalize the character case.
   </para>
  </note>
  <note>
   <para>
    The function <function>realpath</function> will not work for a file which
    is inside a Phar as such path would be a virtual path, not a real one.
   </para>
  </note>
  <note>
   <para>
    On Windows, junctions and symbolic links to directories are only expanded by
    one level.
   </para>
  </note>
  &fs.file.32bit;
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>realpath</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
chdir('/var/www/');
echo realpath('./../../etc/passwd') . PHP_EOL;

echo realpath('/tmp/') . PHP_EOL;
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
/etc/passwd
/tmp
]]>
    </screen>
   </example>
   <example>
    <title><function>realpath</function> on Windows</title>
    <para>
     On windows <function>realpath</function> will change unix style paths to
     windows style.
    </para>
    <programlisting role="php">
<![CDATA[
<?php
echo realpath('/windows/system32'), PHP_EOL;

echo realpath('C:\Program Files\\'), PHP_EOL;
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
C:\WINDOWS\System32
C:\Program Files
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>basename</function></member>
    <member><function>dirname</function></member>
    <member><function>pathinfo</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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