<?xml version="1.0"?>

<!DOCTYPE modulesynopsis SYSTEM "/style/modulesynopsis.dtd">

<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

<modulesynopsis metafile="mod_rewrite.xml.meta">

<name>mod_rewrite</name>

<description>Provides a rule-based rewriting engine to rewrite requested

URLs on the fly</description>

<status>Extension</status>

<sourcefile>mod_rewrite.c</sourcefile>

<identifier>rewrite_module</identifier>

<compatibility>Available in Apache 1.3 and later</compatibility>

<summary>

<p>This module uses a rule-based rewriting engine (based on a

regular-expression parser) to rewrite requested URLs on the

fly. It supports an unlimited number of rules and an

unlimited number of attached rule conditions for each rule, to

provide a really flexible and powerful URL manipulation

mechanism. The URL manipulations can depend on various tests,

of server variables, environment variables, HTTP

headers, or time stamps. Even external database lookups in

various formats can be used to achieve highly granular URL

matching.</p>

<p>This module operates on the full URLs (including the

path-info part) both in per-server context

(<code>httpd.conf</code>) and per-directory context

(<code>.htaccess</code>) and can generate query-string

parts on result. The rewritten result can lead to internal

sub-processing, external request redirection or even to an

internal proxy throughput.</p>

<p>Further details, discussion, and examples, are provided in the

<a href="/rewrite/">detailed mod_rewrite documentation</a>.</p>

</summary>

<section id="quoting"><title>Quoting Special Characters</title>

<p>As of Apache 1.3.20, special characters in

<em>TestString</em> and <em>Substitution</em> strings can be

escaped (that is, treated as normal characters without their

usual special meaning) by prefixing them with a slash ('\')

character. In other words, you can include an actual

dollar-sign character in a <em>Substitution</em> string by

using '<code>\$</code>'; this keeps mod_rewrite from trying

to treat it as a backreference.</p>

</section>

<section id="EnvVar"><title>Environment Variables</title>

<p>This module keeps track of two additional (non-standard)

CGI/SSI environment variables named <code>SCRIPT_URL</code>

and <code>SCRIPT_URI</code>. These contain the

<em>logical</em> Web-view to the current resource, while the

standard CGI/SSI variables <code>SCRIPT_NAME</code> and

<code>SCRIPT_FILENAME</code> contain the <em>physical</em>

System-view. </p>

<p>Notice: These variables hold the URI/URL <em>as they were

initially requested</em>, that is, <em>before</em> any

rewriting. This is important to note because the rewriting process is

primarily used to rewrite logical URLs to physical

pathnames.</p>

<example><title>Example</title>

<pre>

SCRIPT_NAME=/sw/lib/w3s/tree/global/u/rse/.www/index.html

SCRIPT_FILENAME=/u/rse/.www/index.html

SCRIPT_URL=/u/rse/

SCRIPT_URI=http://en1.engelschall.com/u/rse/

</pre>

</example>

</section>

<section id="Solutions"><title>Practical Solutions</title>

<p>For numerous examples of common, and not-so-common, uses for

mod_rewrite, see the <a href="/rewrite/rewrite_guide.html">Rewrite

Guide</a>, and the <a

href="/rewrite/rewrite_guide_advanced.html">Advanced Rewrite

Guide</a> documents.</p>

</section>

<directivesynopsis>

<name>RewriteEngine</name>

<description>Enables or disables runtime rewriting engine</description>

<syntax>RewriteEngine on|off</syntax>

<default>RewriteEngine off</default>

<contextlist><context>server config</context><context>virtual host</context>

<context>directory</context><context>.htaccess</context></contextlist>

<override>FileInfo</override>

<usage>

<p>The <directive>RewriteEngine</directive> 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 <directive

module="mod_rewrite">RewriteRule</directive> directives!</p>

<p>Note that, by default, rewrite configurations are not

inherited. This means that you need to have a

<code>RewriteEngine on</code> directive for each virtual host

in which you wish to use it.</p>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteOptions</name>

<description>Sets some special options for the rewrite engine</description>

<syntax>RewriteOptions <var>Options</var></syntax>

<contextlist><context>server config</context><context>virtual host</context>

<context>directory</context><context>.htaccess</context></contextlist>

<override>FileInfo</override>

<compatibility><code>MaxRedirects</code> is no longer available in version 2.1 and

later</compatibility>

<usage>

<p>The <directive>RewriteOptions</directive> 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>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 are inherited.</dd>

</dl>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteLog</name>

<description>Sets the name of the file used for logging rewrite engine

processing</description>

<syntax>RewriteLog <em>file-path</em></syntax>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The <directive>RewriteLog</directive> directive sets the name

of the file to which the server logs any rewriting actions it

performs. If the name does not begin with a slash

('<code>/</code>') then it is assumed to be relative to the

<em>Server Root</em>. The directive should occur only once per

server config.</p>

<note> To disable the logging of

rewriting actions it is not recommended to set

<em>Filename</em> to <code>/dev/null</code>, because

although the rewriting engine does not then output to a

logfile it still creates the logfile output internally.

<strong>This will slow down the server with no advantage

to the administrator!</strong> To disable logging either

remove or comment out the <directive>RewriteLog</directive>

directive or use <code>RewriteLogLevel 0</code>!

</note>

<note type="securitywarning"><title>Security</title>

See the <a href="/misc/security_tips.html">Apache Security Tips</a>

document for details on how your security could be compromised if the

directory where logfiles are stored is writable by anyone other than

the user that starts the server.

</note>

<example><title>Example</title>

RewriteLog "/usr/local/var/apache/logs/rewrite.log"

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteLogLevel</name>

<description>Sets the verbosity of the log file used by the rewrite

engine</description>

<syntax>RewriteLogLevel <em>Level</em></syntax>

<default>RewriteLogLevel 0</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The <directive>RewriteLogLevel</directive> directive sets the

verbosity level of the rewriting logfile. The default level 0

means no logging, while 9 or more means that practically all

actions are logged.</p>

<p>To disable the logging of rewriting actions simply set

<em>Level</em> to 0. This disables all rewrite action

logs.</p>

<note> Using a high value for

<em>Level</em> will slow down your Apache server

dramatically! Use the rewriting logfile at a

<em>Level</em> greater than 2 only for debugging!

</note>

<example><title>Example</title>

RewriteLogLevel 3

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteLock</name>

<description>Sets the name of the lock file used for <directive

module="mod_rewrite">RewriteMap</directive>

synchronization</description>

<syntax>RewriteLock <em>file-path</em></syntax>

<contextlist><context>server config</context></contextlist>

<usage>

<p>This directive sets the filename for a synchronization

lockfile which mod_rewrite needs to communicate with <directive

module="mod_rewrite">RewriteMap</directive>

<em>programs</em>. Set this lockfile to a local path (not on a

NFS-mounted device) when you want to use a rewriting

map-program. It is not required for other types of rewriting

maps.</p>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteMap</name>

<description>Defines a mapping function for key-lookup</description>

<syntax>RewriteMap <em>MapName</em> <em>MapType</em>:<em>MapSource</em>

</syntax>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<compatibility>The choice of different dbm types is available in

Apache 2.0.41 and later</compatibility>

<usage>

<p>The <directive>RewriteMap</directive> 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.</p>

<p>For example, you might define a

<directive>RewriteMap</directive> as:</p>

<example>

RewriteMap examplemap txt:/path/to/file/map.txt

</example>

<p>You would then be able to use this map in a

<directive>RewriteRule</directive> as follows:</p>

<example>

RewriteRule ^/ex/(.*) ${examplemap:$1}

</example>

<p>The following combinations for <em>MapType</em> and

<em>MapSource</em> can be used:</p>

<ul>

<li>

<strong>Standard Plain Text</strong><br />

MapType: <code>txt</code>, MapSource: Unix filesystem

path to valid regular file

<p>This is the standard rewriting map feature where the

<em>MapSource</em> is a plain ASCII file containing

either blank lines, comment lines (starting with a '#'

character) or pairs like the following - one per

line.</p>

<p class="indent">

<strong><em>MatchingKey</em>

<em>SubstValue</em></strong>

</p>

<example><title>Example</title>

<pre>

##

## map.txt -- rewriting map

##

Ralf.S.Engelschall rse # Bastard Operator From Hell

Mr.Joe.Average joe # Mr. Average

</pre>

</example>

<example>

RewriteMap real-to-user txt:/path/to/file/map.txt

</example>

</li>

<li>

<strong>Randomized Plain Text</strong><br />

MapType: <code>rnd</code>, MapSource: Unix filesystem

path to valid regular file

<p>This is identical to the Standard Plain Text variant

above but with a special post-processing feature: After

looking up a value it is parsed according to contained

``<code>|</code>'' characters which have the meaning of

``or''. In other words they indicate a set of

alternatives from which the actual returned value is

chosen randomly. For example, you might use the following map

file and directives to provide a random load balancing between

several back-end server, via a reverse-proxy. Images are sent

to one of the servers in the 'static' pool, while everything

else is sent to one of the 'dynamic' pool.</p>

<p>Example:</p>

<example><title>Rewrite map file</title>

<pre>

##

## map.txt -- rewriting map

##

static www1|www2|www3|www4

dynamic www5|www6

</pre>

</example>

<example><title>Configuration directives</title>

RewriteMap servers rnd:/path/to/file/map.txt<br />

<br />

RewriteRule ^/(.*\.(png|gif|jpg)) http://${servers:static}/$1

[NC,P,L]<br />

RewriteRule ^/(.*) http://${servers:dynamic}/$1 [P,L]

</example>

</li>

<li>

<strong>Hash File</strong><br /> MapType:

<code>dbm[=<em>type</em>]</code>, MapSource: Unix filesystem

path to valid regular file

<p>Here the source is a binary format DBM file containing

the same contents as a <em>Plain Text</em> format file, but

in a special representation which is optimized for really

fast lookups. The <em>type</em> can be sdbm, gdbm, ndbm, or

db depending on <a href="/install.html#dbm">compile-time

settings</a>. If the <em>type</em> is omitted, the

compile-time default will be chosen. You can create such a

file with any DBM tool or with the following Perl

script. Be sure to adjust it to create the appropriate

type of DBM. The example creates an NDBM file.</p>

<example>

<pre>

#!/path/to/bin/perl

##

## txt2dbm -- convert txt map to dbm format

##

use NDBM_File;

use Fcntl;

($txtmap, $dbmmap) = @ARGV;

open(TXT, "&lt;$txtmap") or die "Couldn't open $txtmap!\n";

tie (%DB, 'NDBM_File', $dbmmap,O_RDWR|O_TRUNC|O_CREAT, 0644)

or die "Couldn't create $dbmmap!\n";

while (&lt;TXT&gt;) {

next if (/^\s*#/ or /^\s*$/);

$DB{$1} = $2 if (/^\s*(\S+)\s+(\S+)/);

}

untie %DB;

close(TXT);

</pre>

</example>

<example>

$ txt2dbm map.txt map.db

</example>

</li>

<li>

<strong>Internal Function</strong><br />

MapType: <code>int</code>, MapSource: Internal Apache

function

<p>Here, the source is an internal Apache function.

Currently you cannot create your own, but the following

functions already exist:</p>

<ul>

<li><strong>toupper</strong>:<br />

Converts the key to all upper case.</li>

<li><strong>tolower</strong>:<br />

Converts the key to all lower case.</li>

<li><strong>escape</strong>:<br />

Translates special characters in the key to

hex-encodings.</li>

<li><strong>unescape</strong>:<br />

Translates hex-encodings in the key back to

special characters.</li>

</ul>

</li>

<li>

<strong>External Rewriting Program</strong><br />

MapType: <code>prg</code>, MapSource: Unix filesystem

path to valid regular file

<p>Here the source is a program, not a map file. To

create it you can use a language of your choice, but

the result has to be an executable program (either

object-code or a script with the magic cookie trick

'<code>#!/path/to/interpreter</code>' as the first

line).</p>

<p>This program is started once, when the Apache server

is started, and then communicates with the rewriting engine

via its <code>stdin</code> and <code>stdout</code>

file-handles. For each map-function lookup it will

receive the key to lookup as a newline-terminated string

on <code>stdin</code>. It then has to give back the

looked-up value as a newline-terminated string on

<code>stdout</code> or the four-character string

``<code>NULL</code>'' if it fails (<em>i.e.</em>, there

is no corresponding value for the given key). A trivial

program which will implement a 1:1 map (<em>i.e.</em>,

key == value) could be:</p>

<example>

<pre>

#!/usr/bin/perl

$| = 1;

while (&lt;STDIN&gt;) {

# ...put here any transformations or lookups...

print $_;

}

</pre>

</example>

<p>But be very careful:</p>

<ol>

<li>``<em>Keep it simple, stupid</em>'' (KISS).

If this program hangs, it will cause Apache to hang

when trying to use the relevant rewrite rule.</li>

<li>A common mistake is to use buffered I/O on

<code>stdout</code>. Avoid this, as it will cause a deadloop!

``<code>$|=1</code>'' is used above, to prevent this.</li>

<li>The <directive

module="mod_rewrite">RewriteLock</directive> directive can

be used to define a lockfile which mod_rewrite can use to synchronize

communication with the mapping program. By default no such

synchronization takes place.</li>

</ol>

</li>

</ul>

<p>The <directive>RewriteMap</directive> directive can occur more than

once. For each mapping-function use one

<directive>RewriteMap</directive> directive to declare its rewriting

mapfile. While you cannot <strong>declare</strong> a map in

per-directory context it is of course possible to

<strong>use</strong> this map in per-directory context. </p>

<note><title>Note</title> For plain text and DBM format files the

looked-up keys are cached in-core until the <code>mtime</code> of the

mapfile changes or the server does a restart. This way you can have

map-functions in rules which are used for <strong>every</strong>

request. This is no problem, because the external lookup only happens

once!

</note>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteBase</name>

<description>Sets the base URL for per-directory rewrites</description>

<syntax>RewriteBase <em>URL-path</em></syntax>

<default>See usage for information.</default>

<contextlist><context>directory</context><context>.htaccess</context>

</contextlist>

<override>FileInfo</override>

<usage>

<p>The <directive>RewriteBase</directive> directive explicitly

sets the base URL for per-directory rewrites. As you will see

below, <directive module="mod_rewrite">RewriteRule</directive>

can be used in per-directory config files

(<code>.htaccess</code>). In such a case, it will act locally,

stripping the local directory prefix before processing, and applying

rewrite rules only to the remainder. When processing is complete, the

prefix is automatically added back to the

path. The default setting is; <directive>RewriteBase</directive> <em>physical-directory-path</em></p>

<p>When a substitution occurs for a new URL, this module has

to re-inject the URL into the server processing. To be able

to do this it needs to know what the corresponding URL-prefix

or URL-base is. By default this prefix is the corresponding

filepath itself. <strong>However, for most websites, URLs are NOT

directly related to physical filename paths, so this

assumption will often be wrong!</strong> Therefore, you can

use the <code>RewriteBase</code> directive to specify the

correct URL-prefix.</p>

<note> If your webserver's URLs are <strong>not</strong> directly

related to physical file paths, you will need to use

<directive>RewriteBase</directive> in every <code>.htaccess</code>

file where you want to use <directive

module="mod_rewrite">RewriteRule</directive> directives.

</note>

<p> For example, assume the following per-directory config file:</p>

<example>

<pre>

#

# /abc/def/.htaccess -- per-dir config file for directory /abc/def

# Remember: /abc/def is the physical path of /xyz, <em>i.e.</em>, the server

# has a 'Alias /xyz /abc/def' directive <em>e.g.</em>

#

RewriteEngine On

# let the server know that we were reached via /xyz and not

# via the physical path prefix /abc/def

RewriteBase /xyz

# now the rewriting rules

RewriteRule ^oldstuff\.html$ newstuff.html

</pre>

</example>

<p>In the above example, a request to

<code>/xyz/oldstuff.html</code> gets correctly rewritten to

the physical file <code>/abc/def/newstuff.html</code>.</p>

<note><title>For Apache Hackers</title>

<p>The following list gives detailed information about

the internal processing steps:</p>

<pre>

Request:

/xyz/oldstuff.html

Internal Processing:

/xyz/oldstuff.html -&gt; /abc/def/oldstuff.html (per-server Alias)

/abc/def/oldstuff.html -&gt; /abc/def/newstuff.html (per-dir RewriteRule)

/abc/def/newstuff.html -&gt; /xyz/newstuff.html (per-dir RewriteBase)

/xyz/newstuff.html -&gt; /abc/def/newstuff.html (per-server Alias)

Result:

/abc/def/newstuff.html

</pre>

<p>This seems very complicated, but is in fact

correct Apache internal processing. Because the

per-directory rewriting comes late in the

process, the rewritten request

has to be re-injected into the Apache kernel.

This is not the serious overhead it may seem to be -

this re-injection is completely internal to the

Apache server (and the same procedure is used by

many other operations within Apache).</p>

</note>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteCond</name>

<description>Defines a condition under which rewriting will take place

</description>

<syntax> RewriteCond

<em>TestString</em> <em>CondPattern</em></syntax>

<contextlist><context>server config</context><context>virtual host</context>

<context>directory</context><context>.htaccess</context></contextlist>

<override>FileInfo</override>

<usage>

<p>The <directive>RewriteCond</directive> directive defines a

rule condition. One or more <directive>RewriteCond</directive>

can precede a <directive module="mod_rewrite">RewriteRule</directive>

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 &lt;= N &lt;= 9), which 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..

</li>

<li>

<strong>RewriteCond backreferences</strong>: These are

backreferences of the form <strong><code>%N</code></strong>

(1 &lt;= N &lt;= 9), which 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.

</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>

<columnspec><column width=".3"/><column width=".3"/>

<column width=".3"/></columnspec>

<tr>

<th>HTTP headers:</th> <th>connection &amp; request:</th> <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></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 />

</td>

</tr>

</table>

<p>These variables all

correspond to the similarly named HTTP

MIME-headers, C variables of the Apache 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>

<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 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 in use (in

the release version of Apache 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.</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

<module>mod_ssl</module> is loaded).</dd>

</dl>

</note>

</li>

</ul>

<p>Other things you should be aware of:</p>

<ol>

<li>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 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>).</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 structures and (if not found there) via

<code>getenv()</code> from the Apache 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

<module>mod_ssl</module> 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>''.</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><strong>Remember:</strong> <em>CondPattern</em> is a

<em>perl compatible regular expression</em> with some

additions:</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>

There are some special variants of <em>CondPatterns</em>.

Instead of real regular expression strings you can also

use one of the following:

<ul>

<li>'<strong>&lt;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>&gt;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>-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>-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>-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.</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>

<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>-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>

</ul>

<note><title>Note:</title>

All of these tests can

also be prefixed by an exclamation mark ('!') to

negate their meaning.

</note>

</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:

<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>

</example>

Without this flag you would have to write the condition/rule

pair three times.

</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>

<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>

</example>

<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>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>RewriteRule</name>

<description>Defines rules for the rewriting engine</description>

<syntax>RewriteRule

<em>Pattern</em> <em>Substitution</em></syntax>

<contextlist><context>server config</context><context>virtual host</context>

<context>directory</context><context>.htaccess</context></contextlist>

<override>FileInfo</override>

<compatibility>The cookie-flag is available in Apache 2.0.40 and later.</compatibility>

<usage>

<p>The <directive>RewriteRule</directive> 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>, which is applied to the current URL.

``Current'' means the value of the URL when this rule is

applied. This may not be the originally requested URL,

which may already have matched a previous rule, and have been

altered.</p>

<p>Some hints on the syntax of <glossary ref="regex">regular

expressions</glossary>:</p>

<note><pre>

<strong>Text:</strong>

<strong><code>.</code></strong> Any single character

<strong><code>[</code></strong>chars<strong><code>]</code></strong> Character class: Any character of the class ``chars''

<strong><code>[^</code></strong>chars<strong><code>]</code></strong> Character class: Not a character of the class ``chars''

text1<strong><code>|</code></strong>text2 Alternative: text1 or text2

<strong>Quantifiers:</strong>

<strong><code>?</code></strong> 0 or 1 occurrences of the preceding text

<strong><code>*</code></strong> 0 or N occurrences of the preceding text (N &gt; 0)

<strong><code>+</code></strong> 1 or N occurrences of the preceding text (N &gt; 1)

<strong>Grouping:</strong>

<strong><code>(</code></strong>text<strong><code>)</code></strong> Grouping of text

(used either to set the borders of an alternative as above, or

to make backreferences, where the <strong>N</strong>th group can

be referred to on the RHS of a RewriteRule as <code>$</code><strong>N</strong>)

<strong>Anchors:</strong>

<strong><code>^</code></strong> Start-of-line anchor

<strong><code>$</code></strong> End-of-line anchor

<strong>Escaping:</strong>

<strong><code>\</code></strong>char escape the given char

(for instance, to specify the chars "<code>.[]()</code>" <em>etc.</em>)

</pre></note>

<p>For more information about regular expressions, have a look at the

perl regular expression manpage ("<a

href="http://www.perldoc.com/perl5.6.1/pod/perlre.html">perldoc

perlre</a>"). If you are interested in more detailed

information about regular expressions and their variants

(POSIX regex etc.) the following book is dedicated to this topic:</p>

<p class="indent">

<em>Mastering Regular Expressions, 2nd Edition</em><br />

Jeffrey E.F. Friedl<br />

O'Reilly &amp; Associates, Inc. 2002<br />

ISBN 0-596-00289-0<br />

</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>

<note><title>Note</title>

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!

</note>

<p>The <a id="rhs" name="rhs"><em>substitution</em></a> of a

rewrite rule is the string which is substituted for (or

replaces) the original URL which <em>Pattern</em>

matched. In addition to plain text, it 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>

<p>There is a special substitution string named

'<code>-</code>' which means: <strong>NO

substitution</strong>! This is useful in providing

rewriting rules which <strong>only</strong> match

URLs but do not substitute anything for them. It is commonly used

in conjunction with the <strong>C</strong> (chain) flag, in order

to apply more than one pattern before substitution occurs.</p>

<p>Additionally you can set special <a name="rewriteflags"

id="rewriteflags">flags</a> for <em>Substitution</em> 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 of any of the

following flags: </p>

<ul>

<li>'<strong><code>chain|C</code></strong>'

(<strong>c</strong>hained with next rule)<br />

This flag chains the current rule with the next rule

(which itself can be chained with the following rule,

and so on). This has the following effect: if a rule

matches, then processing continues as usual -

the flag has no effect. If the rule does

<strong>not</strong> match, then all following chained

rules are skipped. For instance, it can be used to remove the

``<code>.www</code>'' part, inside a per-directory rule set,

when you let an external redirect happen (where the

``<code>.www</code>'' part should not occur!).</li>

<li>

'<strong><code>cookie|CO=</code></strong><em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>]]'

(set <strong>co</strong>okie)<br />

This sets a cookie in the client's browser. The cookie's name

is specified by <em>NAME</em> and the value is

<em>VAL</em>. The <em>domain</em> field is the domain of the

cookie, such as '.apache.org', the optional <em>lifetime</em>

is the lifetime of the cookie in minutes, and the optional

<em>path</em> is the path of the cookie</li>

<li>

'<strong><code>env|E=</code></strong><em>VAR</em>:<em>VAL</em>'

(set <strong>e</strong>nvironment variable)<br />

This forces an environment variable named <em>VAR</em> to

be set to the value <em>VAL</em>, where <em>VAL</em> can

contain regexp backreferences (<code>$N</code> and

<code>%N</code>) which will be expanded. You can use this

flag more than once, to set more than one variable. The

variables can later be dereferenced in many situations, most commonly

from within XSSI (via <code>&lt;!--#echo

var="VAR"--&gt;</code>) or CGI (<code>$ENV{'VAR'}</code>).

You can also dereference the variable in a later RewriteCond pattern, using

<code>%{ENV:VAR}</code>. Use this to strip

information from URLs, while maintaining a record of that information.</li>

<li>'<strong><code>forbidden|F</code></strong>' (force URL

to be <strong>f</strong>orbidden)<br />

This forces the current URL to be forbidden - it immediately

sends back a HTTP response of 403 (FORBIDDEN).

Use this flag in conjunction with

appropriate RewriteConds to conditionally block some

URLs.</li>

<li>'<strong><code>gone|G</code></strong>' (force URL to be

<strong>g</strong>one)<br />

This forces the current URL to be gone - it

immediately sends back a HTTP response of 410 (GONE). Use

this flag to mark pages which no longer exist as gone.</li>

<li>

'<strong><code>handler|H</code></strong>=<em>Content-handler</em>'

(force Content <strong>h</strong>andler)<br />

Force the Content-handler of the target file to be

<em>Content-handler</em>. For instance, this can be used to

simulate the <module>mod_alias</module> directive

<directive module="mod_alias">ScriptAlias</directive>,

which internally forces all files

inside the mapped directory to have a handler of

``<code>cgi-script</code>''.</li>

<li>'<strong><code>last|L</code></strong>'

(<strong>l</strong>ast rule)<br />

Stop the rewriting process here and don't apply any more

rewrite rules. This corresponds to the Perl

<code>last</code> command or the <code>break</code> command

in C. Use this flag to prevent the currently

rewritten URL from being rewritten further by following

rules. For example, use it to rewrite the root-path URL

('<code>/</code>') to a real one, <em>e.g.</em>,

'<code>/e/www/</code>'.</li>

<li>'<strong><code>next|N</code></strong>'

(<strong>n</strong>ext round)<br />

Re-run the rewriting process (starting again with the

first rewriting rule). This time, the URL to match is no longer

the original URL, but rather the URL returned by the last rewriting rule.

This corresponds to the Perl <code>next</code> command or

the <code>continue</code> command in C. Use

this flag to restart the rewriting process -

to immediately go to the top of the loop.<br />

<strong>Be careful not to create an infinite

loop!</strong></li>

<li>'<strong><code>nocase|NC</code></strong>'

(<strong>n</strong>o <strong>c</strong>ase)<br />

This makes the <em>Pattern</em> case-insensitive,

ignoring difference between 'A-Z' and

'a-z' when <em>Pattern</em> is matched against the current

URL.</li>

<li>

'<strong><code>noescape|NE</code></strong>'

(<strong>n</strong>o URI <strong>e</strong>scaping of

output)<br />

This flag prevents mod_rewrite from applying the usual URI

escaping rules to the result of a rewrite. Ordinarily,

special characters (such as '%', '$', ';', and so on)

will be escaped into their hexcode equivalents ('%25',

'%24', and '%3B', respectively); this flag prevents this

from happening. This allows percent symbols to appear in

the output, as in

<example>

RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE]

</example>

which would turn '<code>/foo/zed</code>' into a safe

request for '<code>/bar?arg=P1=zed</code>'.

</li>

<li>

'<strong><code>nosubreq|NS</code></strong>'

(<strong>n</strong>ot for internal

<strong>s</strong>ub-requests)<br />

This flag forces the rewriting engine to skip a

rewriting rule if the current request is an internal

sub-request. For instance, sub-requests occur internally

in Apache when <module>mod_include</module> tries to find out

information about possible directory default files

(<code>index.xxx</code> files). On sub-requests it is not

always useful, and can even cause errors, if

the complete set of rules are applied. Use this flag to

exclude some rules.<br />

To decide whether or not to use this rule: if you

prefix URLs with CGI-scripts, to force them to be

processed by the CGI-script, it's likely that you

will run into problems (or significant overhead) on

sub-requests. In these cases, use this flag.

</li>

<li>

'<strong><code>proxy|P</code></strong>' (force

<strong>p</strong>roxy)<br />

This flag forces the substitution part to be internally

sent as a proxy request and immediately (rewrite

processing stops here) put through the <a

href="mod_proxy.html">proxy module</a>. You must make

sure that the substitution string is a valid URI

(typically starting with

<code>http://</code><em>hostname</em>) which can be

handled by the Apache proxy module. If not, you will get an

error from the proxy module. Use this flag to achieve a

more powerful implementation of the <a

href="mod_proxy.html#proxypass">ProxyPass</a> directive,

to map remote content into the namespace of the local

server.

<p>Note: <module>mod_proxy</module> must be enabled in order

to use this flag.</p>

</li>

<li>

'<strong><code>passthrough|PT</code></strong>'

(<strong>p</strong>ass <strong>t</strong>hrough to next

handler)<br />

This flag forces the rewrite engine to set the

<code>uri</code> field of the internal

<code>request_rec</code> structure to the value of the

<code>filename</code> field. This flag is just a hack to

enable post-processing of the output of

<code>RewriteRule</code> directives, using

<code>Alias</code>, <code>ScriptAlias</code>,

<code>Redirect</code>, and other directives from

various URI-to-filename translators. For example, to rewrite

<code>/abc</code> to <code>/def</code> using

<module>mod_rewrite</module>, and then

<code>/def</code> to <code>/ghi</code> using

<module>mod_alias</module>:

<example>

RewriteRule ^/abc(.*) /def$1 [PT]<br />

Alias /def /ghi

</example>

If you omit the <code>PT</code> flag,

<code>mod_rewrite</code> will rewrite

<code>uri=/abc/...</code> to

<code>filename=/def/...</code> as a full API-compliant

URI-to-filename translator should do. Then

<code>mod_alias</code> will try to do a

URI-to-filename transition, which will fail.

<p>Note: <strong>You must use this flag if you want to

mix directives from different modules which allow

URL-to-filename translators</strong>. The typical example

is the use of <module>mod_alias</module> and

<module>mod_rewrite</module>.</p>

</li>

<li>'<strong><code>qsappend|QSA</code></strong>'

(<strong>q</strong>uery <strong>s</strong>tring

<strong>a</strong>ppend)<br />

This flag forces the rewrite engine to append a query

string part of the substitution string to the existing string,

instead of replacing it. Use this when you want to add more

data to the query string via a rewrite rule.</li>

<li>'<strong><code>redirect|R</code>

[=<em>code</em>]</strong>' (force <a id="redirect"

name="redirect"><strong>r</strong>edirect</a>)<br />

Prefix <em>Substitution</em> with

<code>http://thishost[:thisport]/</code> (which makes the

new URL a URI) to force a external redirection. If no

<em>code</em> is given, a HTTP response of 302 (MOVED

TEMPORARILY) will be returned. If you want to use other response

codes in the range 300-400, simply specify the appropriate number

or use one of the following symbolic names:

<code>temp</code> (default), <code>permanent</code>,

<code>seeother</code>. Use this for rules to

canonicalize the URL and return it to the client - to

translate ``<code>/~</code>'' into

``<code>/u/</code>'', or to always append a slash to

<code>/u/</code><em>user</em>, etc.<br />

<strong>Note:</strong> When you use this flag, make

sure that the substitution field is a valid URL! Otherwise,

you will be redirecting to an invalid location. Remember

that this flag on its own will only prepend

<code>http://thishost[:thisport]/</code> to the URL, and rewriting

will continue. Usually, you will want to stop rewriting at this point,

and redirect immediately. To stop rewriting, you should add

the 'L' flag.

</li>

<li>'<strong><code>skip|S</code></strong>=<em>num</em>'

(<strong>s</strong>kip next rule(s))<br />

This flag forces the rewriting engine to skip the next

<em>num</em> rules in sequence, if the current rule

matches. Use this to make pseudo if-then-else constructs:

The last rule of the then-clause becomes

<code>skip=N</code>, where N is the number of rules in the

else-clause. (This is <strong>not</strong> the same as the

'chain|C' flag!)</li>

<li>

'<strong><code>type|T</code></strong>=<em>MIME-type</em>'

(force MIME <strong>t</strong>ype)<br />

Force the <glossary>MIME-type</glossary> of the target file to be

<em>MIME-type</em>. This can be used to

set up the content-type based on some conditions.

For example, the following snippet allows <code>.php</code> files to

be <em>displayed</em> by <code>mod_php</code> if they are called with

the <code>.phps</code> extension:

<example>

RewriteRule ^(.+\.php)s$ $1 [T=application/x-httpd-php-source]

</example>

</li>

</ul>

<note><title>Note: Enabling rewrites in per-directory context</title>

To enable the rewrite engine

for per-directory configuration files you need to set

``<code>RewriteEngine On</code>'' in these files

<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.

</note>

<note><title>Note: Pattern matching in per-directory context</title>

Never forget that <em>Pattern</em> is

applied to a complete URL in per-server configuration

files. <strong>However, in per-directory configuration 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.</strong> 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.

<p>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!</p>

</note>

<note><title>Note: Substitution of Absolute URLs</title>

<p>

When you prefix a substitution field with

<code>http://thishost[:thisport]</code>, <module

>mod_rewrite</module> will automatically strip that

out. This auto-reduction on URLs with an implicit

external redirect is most useful in

combination with a mapping-function which generates the

hostname part.</p>

<p><strong>Remember:</strong> An unconditional external

redirect to your own server will not work with the prefix

<code>http://thishost</code> because of this feature. To

achieve such a self-redirect, you have to use the

<strong>R</strong>-flag.</p>

</note>

<note><title>Note: Query String</title>

<p>The <em>Pattern</em> will not be matched against the query string.

To do this, you must use a <directive

module="mod_rewrite">RewriteCond</directive> with the

<code>%{QUERY_STRING}</code> variable. 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>

</note>

<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>

<note><pre>

<strong>Given Rule</strong> <strong>Resulting Substitution</strong>

---------------------------------------------- ----------------------------------

^/somepath(.*) otherpath$1 invalid, not supported

^/somepath(.*) otherpath$1 [R] invalid, not supported

^/somepath(.*) otherpath$1 [P] invalid, not supported

---------------------------------------------- ----------------------------------

^/somepath(.*) /otherpath$1 /otherpath/pathinfo

^/somepath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo

via external redirection

^/somepath(.*) /otherpath$1 [P] doesn't make sense, not supported

---------------------------------------------- ----------------------------------

^/somepath(.*) http://thishost/otherpath$1 /otherpath/pathinfo

^/somepath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo

via external redirection

^/somepath(.*) http://thishost/otherpath$1 [P] doesn't make sense, not supported

---------------------------------------------- ----------------------------------

^/somepath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo

via external redirection

^/somepath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo

via external redirection

(the [R] flag is redundant)

^/somepath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo

via internal proxy

</pre></note>

<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>

<note><pre>

<strong>Given Rule</strong> <strong>Resulting Substitution</strong>

---------------------------------------------- ----------------------------------

^localpath(.*) otherpath$1 /somepath/otherpath/pathinfo

^localpath(.*) otherpath$1 [R] http://thishost/somepath/otherpath/pathinfo

via external redirection

^localpath(.*) otherpath$1 [P] doesn't make sense, not supported

---------------------------------------------- ----------------------------------

^localpath(.*) /otherpath$1 /otherpath/pathinfo

^localpath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo

via external redirection

^localpath(.*) /otherpath$1 [P] doesn't make sense, not supported

---------------------------------------------- ----------------------------------

^localpath(.*) http://thishost/otherpath$1 /otherpath/pathinfo

^localpath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo

via external redirection

^localpath(.*) http://thishost/otherpath$1 [P] doesn't make sense, not supported

---------------------------------------------- ----------------------------------

^localpath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo

via external redirection

^localpath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo

via external redirection

(the [R] flag is redundant)

^localpath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo

via internal proxy

</pre></note>

</usage>

</directivesynopsis>

</modulesynopsis>