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|
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
This file is generated from xml source: DO NOT EDIT
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-->
<title>mod_rewrite - Apache HTTP Server</title>
<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<body>
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.3</p>
<img alt="" src="../images/feather.gif" /></div>
<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
<div id="path">
<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
<div id="page-content">
<div id="preamble"><h1>Apache Module mod_rewrite</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_rewrite.html" title="English"> en </a> |
<a href="../fr/mod/mod_rewrite.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Provides a rule-based rewriting engine to rewrite requested
URLs on the fly</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>rewrite_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_rewrite.c</td></tr></table>
<h3>Summary</h3>
<p>The <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> module uses a rule-based rewriting
engine, based on a regular-expression parser, to rewrite requested URLs on
the fly. By default, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> maps a URL to a filesystem
path. However, it can also be used to redirect one URL to another URL, or
to invoke an internal proxy fetch.</p>
<p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> provides a flexible and powerful way to
manipulate URLs using an unlimited number of rules. Each rule can have an
unlimited number of attached rule conditions, to allow you to rewrite URL
based on server variables, environment variables, HTTP headers, or time
stamps.</p>
<p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> operates on the full URL path, including the
path-info section. A rewrite rule can be invoked in
<code>httpd.conf</code> or in <code>.htaccess</code>. The path generated
by a rewrite rule can include a query string, or can lead to internal
sub-processing, external request redirection, or internal proxy
throughput.</p>
<p>Further details, discussion, and examples, are provided in the
<a href="../rewrite/">detailed mod_rewrite documentation</a>.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#rewritebase">RewriteBase</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#rewritecond">RewriteCond</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#rewriteengine">RewriteEngine</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#rewritemap">RewriteMap</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#rewriteoptions">RewriteOptions</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#rewriterule">RewriteRule</a></li>
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#logging">Logging</a></li>
</ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="logging" id="logging">Logging</a></h2>
<p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> offers detailed logging of its actions
at the <code>trace1</code> to <code>trace8</code> log levels. The
log level can be set specifically for <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
using the <code class="directive"><a href="../mod/core.html#loglevel">LogLevel</a></code> directive: Up to
level <code>debug</code>, no actions are logged, while <code>trace8</code>
means that practically all actions are logged.</p>
<div class="note">
Using a high trace log level for <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
will slow down your Apache HTTP Server dramatically! Use a log
level higher than <code>trace2</code> only for debugging!
</div>
<div class="example"><h3>Example</h3><p><code>
LogLevel alert rewrite:trace3
</code></p></div>
<div class="note"><h3>RewriteLog</h3>
<p>Those familiar with earlier versions of
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> will no doubt be looking for the
<code>RewriteLog</code> and <code>RewriteLogLevel</code>
directives. This functionality has been completely replaced by the
new per-module logging configuration mentioned above.
</p>
<p>To get just the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>-specific log
messages, pipe the log file through grep:</p>
<div class="example"><p><code>
tail -f error_log|fgrep '[rewrite:'
</code></p></div>
</div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteBase" id="RewriteBase">RewriteBase</a> <a name="rewritebase" id="rewritebase">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the base URL for per-directory rewrites</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteBase <em>URL-path</em></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>None</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
</table>
<p>The <code class="directive">RewriteBase</code> directive explicitly
sets the base URL-path (not filesystem directory path!) for per-directory rewrites.
When you use a <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
in a <code>.htaccess</code> file, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> strips off
the local directory prefix before processing, then rewrites the rest of
the URL. When the rewrite is completed, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
automatically adds the local directory prefix back on to the path.</p>
<p>This directive is <em>required</em> for per-directory rewrites whose context
is a directory made available via the <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code>
directive.</p>
<p>If your URL path does not exist verbatim on the filesystem,
or isn't directly under your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>,
you must use <code class="directive">RewriteBase</code> in every
<code>.htaccess</code> file where you want to use <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives.</p>
<p>The example below demonstrates how to map
http://example.com/myapp/index.html to
/home/www/example/newsite.html, in a <code>.htaccess</code> file. This
assumes that the content available at
http://example.com/ is on disk at /home/www/example/</p>
<div class="example"><pre>
RewriteEngine On
# The URL-path used to get to this context, not the filesystem path
RewriteBase /myapp/
RewriteRule ^index\.html$ newsite.html
</pre></div>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteCond" id="RewriteCond">RewriteCond</a> <a name="rewritecond" id="rewritecond">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines a condition under which rewriting will take place
</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code> RewriteCond
<em>TestString</em> <em>CondPattern</em></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
</table>
<p>The <code class="directive">RewriteCond</code> directive defines a
rule condition. One or more <code class="directive">RewriteCond</code>
can precede a <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
directive. The following rule is then only used if both
the current state of the URI matches its pattern, <strong>and</strong> if these conditions are met.</p>
<p><em>TestString</em> is a string which can contain the
following expanded constructs in addition to plain text:</p>
<ul>
<li>
<strong>RewriteRule backreferences</strong>: These are
backreferences of the form <strong><code>$N</code></strong>
(0 <= N <= 9). $1 to $9 provide access to the grouped
parts (in parentheses) of the pattern, from the
<code>RewriteRule</code> which is subject to the current
set of <code>RewriteCond</code> conditions. $0 provides
access to the whole string matched by that pattern.
</li>
<li>
<strong>RewriteCond backreferences</strong>: These are
backreferences of the form <strong><code>%N</code></strong>
(0 <= N <= 9). %1 to %9 provide access to the grouped
parts (again, in parentheses) of the pattern, from the last matched
<code>RewriteCond</code> in the current set
of conditions. %0 provides access to the whole string matched by
that pattern.
</li>
<li>
<strong>RewriteMap expansions</strong>: These are
expansions of the form <strong><code>${mapname:key|default}</code></strong>.
See <a href="#mapfunc">the documentation for
RewriteMap</a> for more details.
</li>
<li>
<strong>Server-Variables</strong>: These are variables of
the form
<strong><code>%{</code> <em>NAME_OF_VARIABLE</em>
<code>}</code></strong>
where <em>NAME_OF_VARIABLE</em> can be a string taken
from the following list:
<table>
<tr>
<th>HTTP headers:</th> <th>connection & request:</th> <th />
</tr>
<tr>
<td>
HTTP_USER_AGENT<br />
HTTP_REFERER<br />
HTTP_COOKIE<br />
HTTP_FORWARDED<br />
HTTP_HOST<br />
HTTP_PROXY_CONNECTION<br />
HTTP_ACCEPT<br />
</td>
<td>
REMOTE_ADDR<br />
REMOTE_HOST<br />
REMOTE_PORT<br />
REMOTE_USER<br />
REMOTE_IDENT<br />
REQUEST_METHOD<br />
SCRIPT_FILENAME<br />
PATH_INFO<br />
QUERY_STRING<br />
AUTH_TYPE<br />
</td>
<td />
</tr>
<tr>
<th>server internals:</th> <th>date and time:</th> <th>specials:</th>
</tr>
<tr>
<td>
DOCUMENT_ROOT<br />
SERVER_ADMIN<br />
SERVER_NAME<br />
SERVER_ADDR<br />
SERVER_PORT<br />
SERVER_PROTOCOL<br />
SERVER_SOFTWARE<br />
</td>
<td>
TIME_YEAR<br />
TIME_MON<br />
TIME_DAY<br />
TIME_HOUR<br />
TIME_MIN<br />
TIME_SEC<br />
TIME_WDAY<br />
TIME<br />
</td>
<td>
API_VERSION<br />
THE_REQUEST<br />
REQUEST_URI<br />
REQUEST_FILENAME<br />
IS_SUBREQ<br />
HTTPS<br />
REQUEST_SCHEME<br />
</td>
</tr>
</table>
<p>These variables all
correspond to the similarly named HTTP
MIME-headers, C variables of the Apache HTTP Server or
<code>struct tm</code> fields of the Unix system.
Most are documented elsewhere in the Manual or in
the CGI specification. Those that are special to
mod_rewrite include those below.</p>
<div class="note">
<dl>
<dt><code>IS_SUBREQ</code></dt>
<dd>Will contain the text "true" if the request
currently being processed is a sub-request,
"false" otherwise. Sub-requests may be generated
by modules that need to resolve additional files
or URIs in order to complete their tasks.</dd>
<dt><code>API_VERSION</code></dt>
<dd>This is the version of the Apache httpd module API
(the internal interface between server and
module) in the current httpd build, as defined in
include/ap_mmn.h. The module API version
corresponds to the version of Apache httpd in use (in
the release version of Apache httpd 1.3.14, for
instance, it is 19990320:10), but is mainly of
interest to module authors.</dd>
<dt><code>THE_REQUEST</code></dt>
<dd>The full HTTP request line sent by the
browser to the server (e.g., "<code>GET
/index.html HTTP/1.1</code>"). This does not
include any additional headers sent by the
browser.</dd>
<dt><code>REQUEST_URI</code></dt>
<dd>The resource requested in the HTTP request
line. (In the example above, this would be
"/index.html".)</dd>
<dt><code>REQUEST_FILENAME</code></dt>
<dd>The full local filesystem path to the file or
script matching the request, if this has already
been determined by the server at the time
<code>REQUEST_FILENAME</code> is referenced. Otherwise,
such as when used in virtual host context, the same
value as <code>REQUEST_URI</code>.</dd>
<dt><code>HTTPS</code></dt>
<dd>Will contain the text "on" if the connection is
using SSL/TLS, or "off" otherwise. (This variable
can be safely used regardless of whether or not
<code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is loaded).</dd>
<dt><code>REQUEST_SCHEME</code></dt>
<dd>Will contain the scheme of the request (ususally
"http" or "https"). This value can be influenced with
<code class="directive"><a href="../mod/core.html#servername">ServerName</a></code>.</dd>
</dl>
</div>
</li>
</ul>
<p>If the <em>TestString</em> has the special value <code>expr</code>, the
<em>CondPattern</em> will be treated as a
<a href="../expr.html">ap_expr</a>.</p>
<p>Other things you should be aware of:</p>
<ol>
<li>
<p>The variables SCRIPT_FILENAME and REQUEST_FILENAME
contain the same value - the value of the
<code>filename</code> field of the internal
<code>request_rec</code> structure of the Apache HTTP Server.
The first name is the commonly known CGI variable name
while the second is the appropriate counterpart of
REQUEST_URI (which contains the value of the
<code>uri</code> field of <code>request_rec</code>).</p>
<p>If a substitution occurred and the rewriting continues,
the value of both variables will be updated accordingly.</p>
<p>If used in per-server context (<em>i.e.</em>, before the
request is mapped to the filesystem) SCRIPT_FILENAME and
REQUEST_FILENAME cannot contain the full local filesystem
path since the path is unknown at this stage of processing.
Both variables will initially contain the value of REQUEST_URI
in that case. In order to obtain the full local filesystem
path of the request in per-server context, use an URL-based
look-ahead <code>%{LA-U:REQUEST_FILENAME}</code> to determine
the final value of REQUEST_FILENAME.</p></li>
<li>
<code>%{ENV:variable}</code>, where <em>variable</em> can be
any environment variable, is also available.
This is looked-up via internal
Apache httpd structures and (if not found there) via
<code>getenv()</code> from the Apache httpd server process.</li>
<li>
<code>%{SSL:variable}</code>, where <em>variable</em> is the
name of an <a href="mod_ssl.html#envvars">SSL environment
variable</a>, can be used whether or not
<code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is loaded, but will always expand to
the empty string if it is not. Example:
<code>%{SSL:SSL_CIPHER_USEKEYSIZE}</code> may expand to
<code>128</code>.</li>
<li>
<code>%{HTTP:header}</code>, where <em>header</em> can be
any HTTP MIME-header name, can always be used to obtain the
value of a header sent in the HTTP request.
Example: <code>%{HTTP:Proxy-Connection}</code> is
the value of the HTTP header
``<code>Proxy-Connection:</code>''.
<p>If a HTTP header is used in a condition this header is added to
the Vary header of the response in case the condition evaluates to
to true for the request. It is <strong>not</strong> added if the
condition evaluates to false for the request. Adding the HTTP header
to the Vary header of the response is needed for proper caching.</p>
<p>It has to be kept in mind that conditions follow a short circuit
logic in the case of the '<strong><code>ornext|OR</code></strong>' flag
so that certain conditions might not be evaluated at all.</p></li>
<li>
<code>%{LA-U:variable}</code> can be used for look-aheads which perform
an internal (URL-based) sub-request to determine the final
value of <em>variable</em>. This can be used to access
variable for rewriting which is not available at the current
stage, but will be set in a later phase.
<p>For instance, to rewrite according to the
<code>REMOTE_USER</code> variable from within the
per-server context (<code>httpd.conf</code> file) you must
use <code>%{LA-U:REMOTE_USER}</code> - this
variable is set by the authorization phases, which come
<em>after</em> the URL translation phase (during which mod_rewrite
operates).</p>
<p>On the other hand, because mod_rewrite implements
its per-directory context (<code>.htaccess</code> file) via
the Fixup phase of the API and because the authorization
phases come <em>before</em> this phase, you just can use
<code>%{REMOTE_USER}</code> in that context.</p></li>
<li>
<code>%{LA-F:variable}</code> can be used to perform an internal
(filename-based) sub-request, to determine the final value
of <em>variable</em>. Most of the time, this is the same as
LA-U above.</li>
</ol>
<p><em>CondPattern</em> is the condition pattern,
a regular expression which is applied to the
current instance of the <em>TestString</em>.
<em>TestString</em> is first evaluated, before being matched against
<em>CondPattern</em>.</p>
<p><em>CondPattern</em> is usually a
<em>perl compatible regular expression</em>, but there is
additional syntax available to perform other useful tests against
the <em>Teststring</em>:</p>
<ol>
<li>You can prefix the pattern string with a
'<code>!</code>' character (exclamation mark) to specify a
<strong>non</strong>-matching pattern.</li>
<li>
You can perform lexicographical string comparisons:
<ul>
<li>'<strong><CondPattern</strong>' (lexicographically
precedes)<br />
Treats the <em>CondPattern</em> as a plain string and
compares it lexicographically to <em>TestString</em>. True if
<em>TestString</em> lexicographically precedes
<em>CondPattern</em>.</li>
<li>'<strong>>CondPattern</strong>' (lexicographically
follows)<br />
Treats the <em>CondPattern</em> as a plain string and
compares it lexicographically to <em>TestString</em>. True if
<em>TestString</em> lexicographically follows
<em>CondPattern</em>.</li>
<li>'<strong>=CondPattern</strong>' (lexicographically
equal)<br />
Treats the <em>CondPattern</em> as a plain string and
compares it lexicographically to <em>TestString</em>. True if
<em>TestString</em> is lexicographically equal to
<em>CondPattern</em> (the two strings are exactly
equal, character for character). If <em>CondPattern</em>
is <code>""</code> (two quotation marks) this
compares <em>TestString</em> to the empty string.</li>
<li>'<strong><=CondPattern</strong>' (lexicographically
less than or equal to)<br />
Treats the <em>CondPattern</em> as a plain string and
compares it lexicographically to <em>TestString</em>. True
if <em>TestString</em> lexicographically precedes
<em>CondPattern</em>, or is equal to <em>CondPattern</em>
(the two strings are equal, character for character).</li>
<li>'<strong>>=CondPattern</strong>' (lexicographically
greater than or equal to)<br />
Treats the <em>CondPattern</em> as a plain string and
compares it lexicographically to <em>TestString</em>. True
if <em>TestString</em> lexicographically follows
<em>CondPattern</em>, or is equal to <em>CondPattern</em>
(the two strings are equal, character for character).</li>
</ul></li>
<li>
You can perform integer comparisons:
<ul>
<li>'<strong>-eq</strong>' (is numerically
<strong>eq</strong>ual to)<br />
The <em>TestString</em> is treated as an integer, and is
numerically compared to the <em>CondPattern</em>. True if
the two are numerically equal.</li>
<li>'<strong>-ge</strong>' (is numerically
<strong>g</strong>reater than or <strong>e</strong>qual to)<br />
The <em>TestString</em> is treated as an integer, and is
numerically compared to the <em>CondPattern</em>. True if
the <em>TestString</em> is numerically greater than or equal
to the <em>CondPattern</em>.</li>
<li>'<strong>-gt</strong>' (is numerically
<strong>g</strong>reater <strong>t</strong>han)<br />
The <em>TestString</em> is treated as an integer, and is
numerically compared to the <em>CondPattern</em>. True if
the <em>TestString</em> is numerically greater than
the <em>CondPattern</em>.</li>
<li>'<strong>-le</strong>' (is numerically
<strong>l</strong>ess than or <strong>e</strong>qual to)<br />
The <em>TestString</em> is treated as an integer, and is
numerically compared to the <em>CondPattern</em>. True if
the <em>TestString</em> is numerically less than or equal
to the <em>CondPattern</em>. Avoid confusion with the
<strong>-l</strong> by using the <strong>-L</strong> or
<strong>-h</strong> variant.</li>
<li>'<strong>-lt</strong>' (is numerically
<strong>l</strong>ess <strong>t</strong>han)<br />
The <em>TestString</em> is treated as an integer, and is
numerically compared to the <em>CondPattern</em>. True if
the <em>TestString</em> is numerically less than
the <em>CondPattern</em>. Avoid confusion with the
<strong>-l</strong> by using the <strong>-L</strong> or
<strong>-h</strong> variant.</li>
</ul>
</li>
<li>You can perform various file attribute tests:
<ul>
<li>'<strong>-d</strong>' (is
<strong>d</strong>irectory)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and is a directory.</li>
<li>'<strong>-f</strong>' (is regular
<strong>f</strong>ile)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and is a regular file.</li>
<li>'<strong>-F</strong>' (is existing file, via
subrequest)<br />
Checks whether or not <em>TestString</em> is a valid file,
accessible via all the server's currently-configured
access controls for that path. This uses an internal
subrequest to do the check, so use it with care -
it can impact your server's performance!</li>
<li>'<strong>-H</strong>' (is symbolic link, bash convention)<br />
See <strong>-l</strong>.</li>
<li>'<strong>-l</strong>' (is symbolic
<strong>l</strong>ink)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and is a symbolic link. May also
use the bash convention of <strong>-L</strong> or
<strong>-h</strong> if there's a possibility of confusion
such as when using the <strong>-lt</strong> or
<strong>-le</strong> tests.</li>
<li>'<strong>-L</strong>' (is symbolic link, bash convention)<br />
See <strong>-l</strong>.</li>
<li>'<strong>-s</strong>' (is regular file, with
<strong>s</strong>ize)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and is a regular file with size greater
than zero.</li>
<li>'<strong>-U</strong>' (is existing URL, via
subrequest)<br />
Checks whether or not <em>TestString</em> is a valid URL,
accessible via all the server's currently-configured
access controls for that path. This uses an internal
subrequest to do the check, so use it with care -
it can impact your server's performance!</li>
<li>'<strong>-x</strong>' (has e<strong>x</strong>ecutable
permissions)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and has executable permissions.
These permissions are determined according to
the underlying OS.</li>
</ul>
<div class="note"><h3>Note:</h3>
All of these tests can
also be prefixed by an exclamation mark ('!') to
negate their meaning.
</div>
</li>
<li>
<p>If the <em>TestString</em> has the special value <code>expr</code>, the
<em>CondPattern</em> will be treated as a
<a href="../expr.html">ap_expr</a>.</p>
</li>
<li>You can also set special flags for
<em>CondPattern</em> by appending
<strong><code>[</code><em>flags</em><code>]</code></strong>
as the third argument to the <code>RewriteCond</code>
directive, where <em>flags</em> is a comma-separated list of any of the
following flags:
<ul>
<li>'<strong><code>nocase|NC</code></strong>'
(<strong>n</strong>o <strong>c</strong>ase)<br />
This makes the test case-insensitive - differences
between 'A-Z' and 'a-z' are ignored, both in the
expanded <em>TestString</em> and the <em>CondPattern</em>.
This flag is effective only for comparisons between
<em>TestString</em> and <em>CondPattern</em>. It has no
effect on filesystem and subrequest checks.</li>
<li>
'<strong><code>ornext|OR</code></strong>'
(<strong>or</strong> next condition)<br />
Use this to combine rule conditions with a local OR
instead of the implicit AND. Typical example:
<div class="example"><pre>
RewriteCond %{REMOTE_HOST} ^host1 [OR]
RewriteCond %{REMOTE_HOST} ^host2 [OR]
RewriteCond %{REMOTE_HOST} ^host3
RewriteRule ...some special stuff for any of these hosts...
</pre></div>
Without this flag you would have to write the condition/rule
pair three times.
</li>
<li>'<strong><code>novary|NV</code></strong>'
(<strong>n</strong>o <strong>v</strong>ary)<br />
If a HTTP header is used in the condition, this flag prevents
this header from being added to the Vary header of the response. <br />
Using this flag might break proper caching of the response if
the representation of this response varies on the value of this header.
So this flag should be only used if the meaning of the Vary header
is well understood.
</li>
</ul>
</li>
</ol>
<p><strong>Example:</strong></p>
<p>To rewrite the Homepage of a site according to the
``<code>User-Agent:</code>'' header of the request, you can
use the following: </p>
<div class="example"><pre>
RewriteCond %{HTTP_USER_AGENT} ^Mozilla
RewriteRule ^/$ /homepage.max.html [L]
RewriteCond %{HTTP_USER_AGENT} ^Lynx
RewriteRule ^/$ /homepage.min.html [L]
RewriteRule ^/$ /homepage.std.html [L]
</pre></div>
<p>Explanation: If you use a browser which identifies itself
as 'Mozilla' (including Netscape Navigator, Mozilla etc), then you
get the max homepage (which could include frames, or other special
features).
If you use the Lynx browser (which is terminal-based), then
you get the min homepage (which could be a version designed for
easy, text-only browsing).
If neither of these conditions apply (you use any other browser,
or your browser identifies itself as something non-standard), you get
the std (standard) homepage.</p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteEngine" id="RewriteEngine">RewriteEngine</a> <a name="rewriteengine" id="rewriteengine">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables or disables runtime rewriting engine</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteEngine on|off</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>RewriteEngine off</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
</table>
<p>The <code class="directive">RewriteEngine</code> directive enables or
disables the runtime rewriting engine. If it is set to
<code>off</code> this module does no runtime processing at
all. It does not even update the <code>SCRIPT_URx</code>
environment variables.</p>
<p>Use this directive to disable the module instead of
commenting out all the <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives!</p>
<p>Note that rewrite configurations are not
inherited by virtual hosts. This means that you need to have a
<code>RewriteEngine on</code> directive for each virtual host
in which you wish to use rewrite rules.</p>
<p><code class="directive">RewriteMap</code> directives of the type <code>prg</code>
are not started during server initialization if they're defined in a
context that does not have <code class="directive">RewriteEngine</code> set to
<code>on</code></p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteMap" id="RewriteMap">RewriteMap</a> <a name="rewritemap" id="rewritemap">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines a mapping function for key-lookup</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteMap <em>MapName</em> <em>MapType</em>:<em>MapSource</em>
</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The choice of different dbm types is available in
Apache HTTP Server 2.0.41 and later</td></tr>
</table>
<p>The <code class="directive">RewriteMap</code> directive defines a
<em>Rewriting Map</em> which can be used inside rule
substitution strings by the mapping-functions to
insert/substitute fields through a key lookup. The source of
this lookup can be of various types.</p>
<p>The <a id="mapfunc" name="mapfunc"><em>MapName</em></a> is
the name of the map and will be used to specify a
mapping-function for the substitution strings of a rewriting
rule via one of the following constructs:</p>
<p class="indent">
<strong><code>${</code> <em>MapName</em> <code>:</code>
<em>LookupKey</em> <code>}</code><br />
<code>${</code> <em>MapName</em> <code>:</code>
<em>LookupKey</em> <code>|</code> <em>DefaultValue</em>
<code>}</code></strong>
</p>
<p>When such a construct occurs, the map <em>MapName</em> is
consulted and the key <em>LookupKey</em> is looked-up. If the
key is found, the map-function construct is substituted by
<em>SubstValue</em>. If the key is not found then it is
substituted by <em>DefaultValue</em> or by the empty string
if no <em>DefaultValue</em> was specified. Empty values
behave as if the key was absent, therefore it is not possible
to distinguish between empty-valued keys and absent keys.</p>
<p>For example, you might define a
<code class="directive">RewriteMap</code> as:</p>
<div class="example"><p><code>
RewriteMap examplemap txt:/path/to/file/map.txt
</code></p></div>
<p>You would then be able to use this map in a
<code class="directive">RewriteRule</code> as follows:</p>
<div class="example"><p><code>
RewriteRule ^/ex/(.*) ${examplemap:$1}
</code></p></div>
<p>The following combinations for <em>MapType</em> and
<em>MapSource</em> can be used:</p>
<dl>
<dt>txt</dt>
<dd>A plain text file containing space-separated key-value
pairs, one per line. (<a href="../rewrite/rewritemap.html#txt">Details ...</a>)</dd>
<dt>rnd</dt>
<dd>Randomly selects an entry from a plain text file (<a href="../rewrite/rewritemap.html#rnd">Details ...</a>)</dd>
<dt>dbm</dt>
<dd>Looks up an entry in a dbm file containing name, value
pairs. Hash is constructed from a plain text file format using
the <code><a href="../programs/httxt2dbm.html">httxt2dbm</a></code>
utility. (<a href="../rewrite/rewritemap.html#dbm">Details ...</a>)</dd>
<dt>int</dt>
<dd>One of the four available internal functions provided by
<code>RewriteMap</code>: toupper, tolower, escape or
unescape. (<a href="../rewrite/rewritemap.html#int">Details ...</a>)</dd>
<dt>prg</dt>
<dd>Calls an external program or script to process the
rewriting. (<a href="../rewrite/rewritemap.html#prg">Details ...</a>)</dd>
<dt>dbd or fastdbd</dt>
<dd>A SQL SELECT statement to be performed to look up the
rewrite target. (<a href="../rewrite/rewritemap.html#dbd">Details ...</a>)</dd>
</dl>
<p>Further details, and numerous examples, may be found in the <a href="../rewrite/rewritemap.html">RewriteMap HowTo</a></p>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteOptions" id="RewriteOptions">RewriteOptions</a> <a name="rewriteoptions" id="rewriteoptions">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets some special options for the rewrite engine</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteOptions <var>Options</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td><code>MaxRedirects</code> is no longer available in version 2.1 and
later</td></tr>
</table>
<p>The <code class="directive">RewriteOptions</code> directive sets some
special options for the current per-server or per-directory
configuration. The <em>Option</em> string can currently
only be one of the following:</p>
<dl>
<dt><code>Inherit</code></dt>
<dd>
<p>This forces the current configuration to inherit the
configuration of the parent. In per-virtual-server context,
this means that the maps, conditions and rules of the main
server are inherited. In per-directory context this means
that conditions and rules of the parent directory's
<code>.htaccess</code> configuration or
<code class="directive"><a href="../mod/core.html#directory"><Directory></a></code>
sections are inherited. The inherited rules are virtually copied
to the section where this directive is being used. If used in
combination with local rules, the inherited rules are copied behind
the local rules. The position of this directive - below or above
of local rules - has no influence on this behavior. If local
rules forced the rewriting to stop, the inherited rules won't
be processed.</p>
<div class="warning">
Rules inherited from the parent scope are applied
<strong>after</strong> rules specified in the child scope.
</div>
</dd>
<dt><code>InheritBefore</code></dt>
<dd>
<p> Like <code>Inherit</code> above, but the rules from the parent scope
are applied <strong>before</strong> rules specified in the child scope.
Available in Apache HTTP Server 2.3.10 and later.</p>
</dd>
</dl>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="RewriteRule" id="RewriteRule">RewriteRule</a> <a name="rewriterule" id="rewriterule">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines rules for the rewriting engine</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteRule
<em>Pattern</em> <em>Substitution</em> [<em>flags</em>]</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
</table>
<p>The <code class="directive">RewriteRule</code> directive is the real
rewriting workhorse. The directive can occur more than once,
with each instance defining a single rewrite rule. The
order in which these rules are defined is important - this is the order
in which they will be applied at run-time.</p>
<p><a id="patterns" name="patterns"><em>Pattern</em></a> is
a perl compatible <a id="regexp" name="regexp">regular
expression</a>. On the first RewriteRule it is applied to the (%-encoded)
<a href="./directive-dict.html#Syntax">URL-path</a> of the request;
subsequent patterns are applied to the output of the last matched
RewriteRule.</p>
<div class="note"><h3>What is matched?</h3>
<p>The <em>Pattern</em> will initially be matched against the part of the
URL after the hostname and port, and before the query string.</p>
<p>When the RewriteRule appears in per-directory (htaccess) context, the
<em>Pattern</em> is matched against what remains of the URL after removing
the prefix that lead Apache httpd to the current rules (see the
<code class="directive"><a href="#rewritebase">RewriteBase</a></code>). The removed prefix
always ends with a slash, meaning the matching occurs against a string which
never has a leading slash. A <em>Pattern</em> with <code>^/</code> never
matches in per-directory context.</p>
<p>If you wish to match against the hostname, port, or query string, use a
<code class="directive"><a href="#rewritecond">RewriteCond</a></code> with the
<code>%{HTTP_HOST}</code>, <code>%{SERVER_PORT}</code>, or
<code>%{QUERY_STRING}</code> variables respectively. If you wish to
match against the full URL-path in a per-directory (htaccess) RewriteRule,
use the <code>%{REQUEST_URI}</code> variable.</p>
</div>
<p>For some hints on <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
expressions</a>, see
the <a href="../rewrite/intro.html#regex">mod_rewrite
Introduction</a>.</p>
<p>In mod_rewrite, the NOT character
('<code>!</code>') is also available as a possible pattern
prefix. This enables you to negate a pattern; to say, for instance:
``<em>if the current URL does <strong>NOT</strong> match this
pattern</em>''. This can be used for exceptional cases, where
it is easier to match the negative pattern, or as a last
default rule.</p>
<div class="note"><h3>Note</h3>
When using the NOT character to negate a pattern, you cannot include
grouped wildcard parts in that pattern. This is because, when the
pattern does NOT match (ie, the negation matches), there are no
contents for the groups. Thus, if negated patterns are used, you
cannot use <code>$N</code> in the substitution string!
</div>
<p>The <a id="rhs" name="rhs"><em>Substitution</em></a> of a
rewrite rule is the string that replaces the original URL-path that
was matched by <em>Pattern</em>. The <em>Substitution</em> may
be a:</p>
<dl>
<dt>file-system path</dt>
<dd>Designates the location on the file-system of the resource
to be delivered to the client.</dd>
<dt>URL-path</dt>
<dd>A <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>-relative path to the
resource to be served. Note that <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
tries to guess whether you have specified a file-system path
or a URL-path by checking to see if the first segment of the
path exists at the root of the file-system. For example, if
you specify a <em>Substitution</em> string of
<code>/www/file.html</code>, then this will be treated as a
URL-path <em>unless</em> a directory named <code>www</code>
exists at the root or your file-system, in which case it will
be treated as a file-system path. If you wish other
URL-mapping directives (such as <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code>) to be applied to the
resulting URL-path, use the <code>[PT]</code> flag as
described below.</dd>
<dt>Absolute URL</dt>
<dd>If an absolute URL is specified,
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> checks to see whether the
hostname matches the current host. If it does, the scheme and
hostname are stripped out and the resulting path is treated as
a URL-path. Otherwise, an external redirect is performed for
the given URL. To force an external redirect back to the
current host, see the <code>[R]</code> flag below.</dd>
<dt><code>-</code> (dash)</dt>
<dd>A dash indicates that no substitution should be performed
(the existing path is passed through untouched). This is used
when a flag (see below) needs to be applied without changing
the path.</dd>
</dl>
<p>In addition to plain text, the <em>Substition</em> string can include</p>
<ol>
<li>back-references (<code>$N</code>) to the RewriteRule
pattern</li>
<li>back-references (<code>%N</code>) to the last matched
RewriteCond pattern</li>
<li>server-variables as in rule condition test-strings
(<code>%{VARNAME}</code>)</li>
<li><a href="#mapfunc">mapping-function</a> calls
(<code>${mapname:key|default}</code>)</li>
</ol>
<p>Back-references are identifiers of the form
<code>$</code><strong>N</strong>
(<strong>N</strong>=0..9), which will be replaced
by the contents of the <strong>N</strong>th group of the
matched <em>Pattern</em>. The server-variables are the same
as for the <em>TestString</em> of a <code>RewriteCond</code>
directive. The mapping-functions come from the
<code>RewriteMap</code> directive and are explained there.
These three types of variables are expanded in the order above.</p>
<p>As already mentioned, all rewrite rules are
applied to the <em>Substitution</em> (in the order in which
they are defined
in the config file). The URL is <strong>completely
replaced</strong> by the <em>Substitution</em> and the
rewriting process continues until all rules have been applied,
or it is explicitly terminated by a
<code><strong>L</strong></code> flag.</p>
<div class="note"><h3>Modifying the Query String</h3>
<p>By default, the query string is passed through unchanged. You
can, however, create URLs in the substitution string containing
a query string part. Simply use a question mark inside the
substitution string to indicate that the following text should
be re-injected into the query string. When you want to erase an
existing query string, end the substitution string with just a
question mark. To combine new and old query strings, use the
<code>[QSA]</code> flag.</p>
</div>
<p>Additionally you can set special <a name="rewriteflags" id="rewriteflags">actions</a> to be performed by
appending <strong><code>[</code><em>flags</em><code>]</code></strong>
as the third argument to the <code>RewriteRule</code>
directive. <em>Flags</em> is a comma-separated list, surround by square
brackets, of any of the flags in the following table. More
details, and examples, for each flag, are available in the <a href="../rewrite/flags.html">Rewrite Flags document</a>.</p>
<table class="bordered">
<tr><th>Flag and syntax</th>
<th>Function</th>
</tr>
<tr>
<td>B</td>
<td>Escape non-alphanumeric characters <em>before</em> applying
the transformation. <em><a href="../rewrite/flags.html#flag_b">details ...</a></em></td>
</tr>
<tr>
<td>chain|C</td>
<td>Rule is chained to the following rule. If the rule fails,
the rule(s) chained to it will be skipped. <em><a href="../rewrite/flags.html#flag_c">details ...</a></em></td>
</tr>
<tr>
<td>cookie|CO=<em>NAME</em>:<em>VAL</em></td>
<td>Sets a cookie in the client browser. Full syntax is:
CO=<em>NAME</em>:<em>VAL</em>[:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>[:<em>secure</em>[:<em>httponly</em>]]]]] <em><a href="../rewrite/flags.html#flag_co">details ...</a></em>
</td>
</tr>
<tr>
<td>discardpathinfo|DPI</td>
<td>Causes the PATH_INFO portion of the rewritten URI to be
discarded. <em><a href="../rewrite/flags.html#flag_dpi">details
...</a></em></td>
</tr>
<tr>
<td>env|E=[!]<em>VAR</em>[:<em>VAL</em>]</td>
<td>Causes an environment variable <em>VAR</em> to be set (to the
value <em>VAL</em> if provided). The form !<em>VAR</em> causes
the environment variable <em>VAR</em> to be unset.<em><a href="../rewrite/flags.html#flag_e">details ...</a></em></td>
</tr>
<tr>
<td>forbidden|F</td>
<td>Returns a 403 FORBIDDEN response to the client browser.
<em><a href="../rewrite/flags.html#flag_f">details ...</a></em></td>
</tr>
<tr>
<td>gone|G</td>
<td>Returns a 410 GONE response to the client browser. <em><a href="../rewrite/flags.html#flag_g">details ...</a></em></td>
</tr>
<tr>
<td>Handler|H=<em>Content-handler</em></td>
<td>Causes the resulting URI to be sent to the specified
<em>Content-handler</em> for processing. <em><a href="../rewrite/flags.html#flag_h">details ...</a></em></td>
</tr>
<tr>
<td>last|L</td>
<td>Stop the rewriting process immediately and don't apply any
more rules. Especially note caveats for per-directory and
.htaccess context (see also the END flag). <em><a href="../rewrite/flags.html#flag_l">details ...</a></em></td>
</tr>
<tr>
<td>next|N</td>
<td>Re-run the rewriting process, starting again with the first
rule, using the result of the ruleset so far as a starting
point. <em><a href="../rewrite/flags.html#flag_n">details
...</a></em></td>
</tr>
<tr>
<td>nocase|NC</td>
<td>Makes the pattern pattern comparison case-insensitive.
<em><a href="../rewrite/flags.html#flag_nc">details ...</a></em></td>
</tr>
<tr>
<td>noescape|NE</td>
<td>Prevent mod_rewrite from applying hexcode escaping of
special characters in the result of the rewrite. <em><a href="../rewrite/flags.html#flag_ne">details ...</a></em></td>
</tr>
<tr>
<td>nosubreq|NS</td>
<td>Causes a rule to be skipped if the current request is an
internal sub-request. <em><a href="../rewrite/flags.html#flag_ns">details ...</a></em></td>
</tr>
<tr>
<td>proxy|P</td>
<td>Force the substitution URL to be internally sent as a proxy
request. <em><a href="../rewrite/flags.html#flag_p">details
...</a></em></td>
</tr>
<tr>
<td>passthrough|PT</td>
<td>Forces the resulting URI to be passed back to the URL
mapping engine for processing of other URI-to-filename
translators, such as <code>Alias</code> or
<code>Redirect</code>. <em><a href="../rewrite/flags.html#flag_pt">details ...</a></em></td>
</tr>
<tr>
<td>qsappend|QSA</td>
<td>Appends any query string created in the rewrite target to
any query string that was in the original request URL. <em><a href="../rewrite/flags.html#flag_qsa">details ...</a></em></td>
</tr>
<tr>
<td>qsdiscard|QSD</td>
<td>Discard any query string attached to the incoming URI.
<em><a href="../rewrite/flags.html#flag_qsd">details
...</a></em></td>
</tr>
<tr>
<td>redirect|R[=<em>code</em>]</td>
<td>Forces an external redirect, optionally with the specified
HTTP status code. <em><a href="../rewrite/flags.html#flag_r">details ...</a></em>
</td>
</tr>
<tr>
<td>END</td>
<td>Stop the rewriting process immediately and don't apply any
more rules. Also prevents further execution of rewrite rules
in per-directory and .htaccess context. (Available in 2.3.9 and later)
<em><a href="../rewrite/flags.html#flag_l">details ...</a></em></td>
</tr>
<tr>
<td>skip|S=<em>num</em></td>
<td>Tells the rewriting engine to skip the next <em>num</em>
rules if the current rule matches. <em><a href="../rewrite/flags.html#flag_s">details ...</a></em></td>
</tr>
<tr>
<td>tyle|T=<em>MIME-type</em></td>
<td>Force the <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME-type</a> of the target file
to be the specified type. <em><a href="../rewrite/flags.html#flag_t">details ...</a></em></td>
</tr>
</table>
<div class="note"><h3>Home directory expansion</h3>
<p> When the substitution string begins with a string
resembling "/~user" (via explicit text or backreferences), mod_rewrite performs
home directory expansion independent of the presence or configuration
of <code class="module"><a href="../mod/mod_userdir.html">mod_userdir</a></code>.</p>
<p> This expansion does not occur when the <em>PT</em>
flag is used on the <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
directive.</p>
</div>
<div class="note"><h3>Per-directory Rewrites</h3>
<p>The rewrite engine may be used in <a href="../howto/htaccess.html">.htaccess</a> files. To enable the
rewrite engine for these files you need to set
"<code>RewriteEngine On</code>" <strong>and</strong>
"<code>Options FollowSymLinks</code>" must be enabled. If your
administrator has disabled override of <code>FollowSymLinks</code> for
a user's directory, then you cannot use the rewrite engine. This
restriction is required for security reasons.</p>
<p>When using the rewrite engine in <code>.htaccess</code> files the
per-directory prefix (which always is the same for a specific
directory) is automatically <em>removed</em> for the pattern matching
and automatically <em>added</em> after the substitution has been
done. This feature is essential for many sorts of rewriting; without
this, you would always have to match the parent directory, which is
not always possible. There is one exception: If a substitution string
starts with <code>http://</code>, then the directory prefix will
<strong>not</strong> be added, and an external redirect (or proxy
throughput, if using flag <strong>P</strong>) is forced. See the
<code class="directive"><a href="#rewritebase">RewriteBase</a></code> directive for
more information.</p>
<p>The rewrite engine may also be used in <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> sections with the same
prefix-matching rules as would be applied to <code>.htaccess</code>
files. It is usually simpler, however, to avoid the prefix substitution
complication by putting the rewrite rules in the main server or
virtual host context, rather than in a <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> section.</p>
<p>Although rewrite rules are syntactically permitted in <code class="directive"><a href="../mod/core.html#location"><Location></a></code> and <code class="directive"><a href="../mod/core.html#files"><Files></a></code> sections, this
should never be necessary and is unsupported.</p>
</div>
<p>Here are all possible substitution combinations and their
meanings:</p>
<p><strong>Inside per-server configuration
(<code>httpd.conf</code>)<br />
for request ``<code>GET
/somepath/pathinfo</code>'':</strong><br />
</p>
<table class="bordered">
<tr>
<th>Given Rule</th>
<th>Resulting Substitution</th>
</tr>
<tr>
<td>^/somepath(.*) otherpath$1</td>
<td>invalid, not supported</td>
</tr>
<tr>
<td>^/somepath(.*) otherpath$1 [R]</td>
<td>invalid, not supported</td>
</tr>
<tr>
<td>^/somepath(.*) otherpath$1 [P]</td>
<td>invalid, not supported</td>
</tr>
<tr>
<td>^/somepath(.*) /otherpath$1</td>
<td>/otherpath/pathinfo</td>
</tr>
<tr>
<td>^/somepath(.*) /otherpath$1 [R]</td>
<td>http://thishost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^/somepath(.*) /otherpath$1 [P]</td>
<td>doesn't make sense, not supported</td>
</tr>
<tr>
<td>^/somepath(.*) http://thishost/otherpath$1</td>
<td>/otherpath/pathinfo</td>
</tr>
<tr>
<td>^/somepath(.*) http://thishost/otherpath$1 [R]</td>
<td>http://thishost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^/somepath(.*) http://thishost/otherpath$1 [P]</td>
<td>doesn't make sense, not supported</td>
</tr>
<tr>
<td>^/somepath(.*) http://otherhost/otherpath$1</td>
<td>http://otherhost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^/somepath(.*) http://otherhost/otherpath$1 [R]</td>
<td>http://otherhost/otherpath/pathinfo via external redirection (the [R] flag is redundant)</td>
</tr>
<tr>
<td>^/somepath(.*) http://otherhost/otherpath$1 [P]</td>
<td>http://otherhost/otherpath/pathinfo via internal proxy</td>
</tr>
</table>
<p><strong>Inside per-directory configuration for
<code>/somepath</code><br />
(<code>/physical/path/to/somepath/.htacccess</code>, with
<code>RewriteBase /somepath</code>)<br />
for request ``<code>GET
/somepath/localpath/pathinfo</code>'':</strong><br />
</p>
<table class="bordered">
<tr>
<th>Given Rule</th>
<th>Resulting Substitution</th>
</tr>
<tr>
<td>^localpath(.*) otherpath$1</td>
<td>/somepath/otherpath/pathinfo</td>
</tr>
<tr>
<td>^localpath(.*) otherpath$1 [R]</td>
<td>http://thishost/somepath/otherpath/pathinfo via external
redirection</td>
</tr>
<tr>
<td>^localpath(.*) otherpath$1 [P]</td>
<td>doesn't make sense, not supported</td>
</tr>
<tr>
<td>^localpath(.*) /otherpath$1</td>
<td>/otherpath/pathinfo</td>
</tr>
<tr>
<td>^localpath(.*) /otherpath$1 [R]</td>
<td>http://thishost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^localpath(.*) /otherpath$1 [P]</td>
<td>doesn't make sense, not supported</td>
</tr>
<tr>
<td>^localpath(.*) http://thishost/otherpath$1</td>
<td>/otherpath/pathinfo</td>
</tr>
<tr>
<td>^localpath(.*) http://thishost/otherpath$1 [R]</td>
<td>http://thishost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^localpath(.*) http://thishost/otherpath$1 [P]</td>
<td>doesn't make sense, not supported</td>
</tr>
<tr>
<td>^localpath(.*) http://otherhost/otherpath$1</td>
<td>http://otherhost/otherpath/pathinfo via external redirection</td>
</tr>
<tr>
<td>^localpath(.*) http://otherhost/otherpath$1 [R]</td>
<td>http://otherhost/otherpath/pathinfo via external redirection (the [R] flag is redundant)</td>
</tr>
<tr>
<td>^localpath(.*) http://otherhost/otherpath$1 [P]</td>
<td>http://otherhost/otherpath/pathinfo via internal proxy</td>
</tr>
</table>
</div>
</div>
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