fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<?xml version="1.0"?>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<!DOCTYPE modulesynopsis SYSTEM "/style/modulesynopsis.dtd">

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

ad74a0524a06bfe11b7de9e3b4ce7233ab3bd3f7nd

d05d0eb4ae6d2a5e513fc3bf2555ce33da416634nd<modulesynopsis metafile="mod_rewrite.xml.meta">

7f5b59ccc63c0c0e3e678a168f09ee6a2f51f9d0nd

7f5b59ccc63c0c0e3e678a168f09ee6a2f51f9d0nd<name>mod_rewrite</name>

3b3b7fc78d1f5bfc2769903375050048ff41ff26nd

3b3b7fc78d1f5bfc2769903375050048ff41ff26nd<description>Provides a rule-based rewriting engine to rewrite requested

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessURLs on the fly</description>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<status>Extension</status>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<sourcefile>mod_rewrite.c</sourcefile>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<identifier>rewrite_module</identifier>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<compatibility>Available in Apache 1.3 and later</compatibility>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end<summary>

5a58787efeb02a1c3f06569d019ad81fd2efa06end <blockquote>

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p>``The great thing about mod_rewrite is it gives you

5a58787efeb02a1c3f06569d019ad81fd2efa06end all the configurability and flexibility of Sendmail.

5a58787efeb02a1c3f06569d019ad81fd2efa06end The downside to mod_rewrite is that it gives you all

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the configurability and flexibility of Sendmail.''</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p class="cite">-- <cite>Brian Behlendorf</cite><br />

5a58787efeb02a1c3f06569d019ad81fd2efa06end Apache Group</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end </blockquote>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end <blockquote>

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p>`` Despite the tons of examples and docs,

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen mod_rewrite is voodoo. Damned cool voodoo, but still

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen voodoo. ''</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p class="cite">-- <cite>Brian Moore</cite><br />

5a58787efeb02a1c3f06569d019ad81fd2efa06end bem@news.cmc.net</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end </blockquote>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p>Welcome to mod_rewrite, the Swiss Army Knife of URL

5a58787efeb02a1c3f06569d019ad81fd2efa06end manipulation!</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This module uses a rule-based rewriting engine (based on a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess regular-expression parser) to rewrite requested URLs on the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess fly. It supports an unlimited number of rules and an

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess unlimited number of attached rule conditions for each rule to

261c62b53a9c707c64c7824eed68b5463bd23e62nd provide a really flexible and powerful URL manipulation

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess mechanism. The URL manipulations can depend on various tests,

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess for instance server variables, environment variables, HTTP

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess headers, time stamps and even external database lookups in

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess various formats can be used to achieve a really granular URL

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess matching.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This module operates on the full URLs (including the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess path-info part) both in per-server context

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess (<code>httpd.conf</code>) and per-directory context

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess (<code>.htaccess</code>) and can even generate query-string

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess parts on result. The rewritten result can lead to internal

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess sub-processing, external request redirection or even to an

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess internal proxy throughput.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>But all this functionality and flexibility has its

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess drawback: complexity. So don't expect to understand this

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess entire module in just one day.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This module was invented and originally written in April

dcf73e82ff6eda04fc24e50753631fd83bf61f3drbowen 1996 and gifted exclusively to the The Apache Group in July 1997

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess by</p>

dcf73e82ff6eda04fc24e50753631fd83bf61f3drbowen

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p class="indent">

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <a href="http://www.engelschall.com/"><code>Ralf S.

261c62b53a9c707c64c7824eed68b5463bd23e62nd Engelschall</code></a><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess href="mailto:rse@engelschall.com"><code>rse@engelschall.com</code></a><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess href="http://www.engelschall.com/"><code>www.engelschall.com</code></a>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</summary>

dcf73e82ff6eda04fc24e50753631fd83bf61f3drbowen

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="Internal"><title>Internal Processing</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

261c62b53a9c707c64c7824eed68b5463bd23e62nd <p>The internal processing of this module is very complex but

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess needs to be explained once even to the average user to avoid

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess common mistakes and to let you exploit its full

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess functionality.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="InternalAPI"><title>API Phases</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>First you have to understand that when Apache processes a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess HTTP request it does this in phases. A hook for each of these

261c62b53a9c707c64c7824eed68b5463bd23e62nd phases is provided by the Apache API. Mod_rewrite uses two of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess these hooks: the URL-to-filename translation hook which is

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess used after the HTTP request has been read but before any

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess authorization starts and the Fixup hook which is triggered

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess after the authorization phases and after the per-directory

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess config files (<code>.htaccess</code>) have been read, but

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess before the content handler is activated.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>So, after a request comes in and Apache has determined the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess corresponding server (or virtual server) the rewriting engine

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess starts processing of all mod_rewrite directives from the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess per-server configuration in the URL-to-filename phase. A few

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess steps later when the final data directories are found, the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess per-directory configuration directives of mod_rewrite are

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess triggered in the Fixup phase. In both situations mod_rewrite

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rewrites URLs either to new URLs or to filenames, although

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess there is no obvious distinction between them. This is a usage

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess of the API which was not intended to be this way when the API

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess was designed, but as of Apache 1.x this is the only way

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess mod_rewrite can operate. To make this point more clear

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess remember the following two points:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <ol>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li>Although mod_rewrite rewrites URLs to URLs, URLs to

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess filenames and even filenames to filenames, the API

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess currently provides only a URL-to-filename hook. In Apache

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess 2.0 the two missing hooks will be added to make the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess processing more clear. But this point has no drawbacks for

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the user, it is just a fact which should be remembered:

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Apache does more in the URL-to-filename hook than the API

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess intends for it.</li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fd98d2e18dca5790daa7e49b4384937e6ba7666cerikabele <li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Unbelievably mod_rewrite provides URL manipulations in

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess per-directory context, <em>i.e.</em>, within

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>.htaccess</code> files, although these are reached

5a58787efeb02a1c3f06569d019ad81fd2efa06end a very long time after the URLs have been translated to

5a58787efeb02a1c3f06569d019ad81fd2efa06end filenames. It has to be this way because

5a58787efeb02a1c3f06569d019ad81fd2efa06end <code>.htaccess</code> files live in the filesystem, so

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess processing has already reached this stage. In other

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess words: According to the API phases at this time it is too

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess late for any URL manipulations. To overcome this chicken

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess and egg problem mod_rewrite uses a trick: When you

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess manipulate a URL/filename in per-directory context

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess mod_rewrite first rewrites the filename back to its

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess corresponding URL (which is usually impossible, but see

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the <code>RewriteBase</code> directive below for the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess trick to achieve this) and then initiates a new internal

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess sub-request with the new URL. This restarts processing of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the API phases.

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Again mod_rewrite tries hard to make this complicated

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess step totally transparent to the user, but you should

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess remember here: While URL manipulations in per-server

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess context are really fast and efficient, per-directory

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rewrites are slow and inefficient due to this chicken and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess egg problem. But on the other hand this is the only way

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess mod_rewrite can provide (locally restricted) URL

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess manipulations to the average user.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </ol>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Don't forget these two points!</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="InternalRuleset"><title>Ruleset Processing</title>

261c62b53a9c707c64c7824eed68b5463bd23e62nd

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Now when mod_rewrite is triggered in these two API phases, it

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess reads the configured rulesets from its configuration

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess structure (which itself was either created on startup for

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess per-server context or during the directory walk of the Apache

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess kernel for per-directory context). Then the URL rewriting

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess engine is started with the contained ruleset (one or more

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rules together with their conditions). The operation of the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess URL rewriting engine itself is exactly the same for both

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess configuration contexts. Only the final result processing is

261c62b53a9c707c64c7824eed68b5463bd23e62nd different. </p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The order of rules in the ruleset is important because the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rewriting engine processes them in a special (and not very

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess obvious) order. The rule is this: The rewriting engine loops

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess through the ruleset rule by rule (<directive

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess module="mod_rewrite">RewriteRule</directive> directives) and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess when a particular rule matches it optionally loops through

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess existing corresponding conditions (<code>RewriteCond</code>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess directives). For historical reasons the conditions are given

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess first, and so the control flow is a little bit long-winded. See

261c62b53a9c707c64c7824eed68b5463bd23e62nd Figure 1 for more details.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<p class="figure">

5a58787efeb02a1c3f06569d019ad81fd2efa06end <img src="/images/mod_rewrite_fig1.gif" width="428"

5a58787efeb02a1c3f06569d019ad81fd2efa06end height="385" alt="[Needs graphics capability to display]" /><br />

5a58787efeb02a1c3f06569d019ad81fd2efa06end <dfn>Figure 1:</dfn>The control flow through the rewriting ruleset

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>As you can see, first the URL is matched against the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Pattern</em> of each rule. When it fails mod_rewrite

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess immediately stops processing this rule and continues with the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess next rule. If the <em>Pattern</em> matches, mod_rewrite looks

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess for corresponding rule conditions. If none are present, it

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess just substitutes the URL with a new value which is

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess constructed from the string <em>Substitution</em> and goes on

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess with its rule-looping. But if conditions exist, it starts an

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess inner loop for processing them in the order that they are

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess listed. For conditions the logic is different: we don't match

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess a pattern against the current URL. Instead we first create a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess string <em>TestString</em> by expanding variables,

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess back-references, map lookups, <em>etc.</em> and then we try

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess to match <em>CondPattern</em> against it. If the pattern

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess doesn't match, the complete set of conditions and the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess corresponding rule fails. If the pattern matches, then the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess next condition is processed until no more conditions are

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess available. If all conditions match, processing is continued

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess with the substitution of the URL with

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Substitution</em>.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="quoting"><title>Quoting Special Characters</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>As of Apache 1.3.20, special characters in

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>TestString</em> and <em>Substitution</em> strings can be

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess escaped (that is, treated as normal characters without their

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess usual special meaning) by prefixing them with a slosh ('\')

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess character. In other words, you can include an actual

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess dollar-sign character in a <em>Substitution</em> string by

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess using '<code>\$</code>'; this keeps mod_rewrite from trying

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess to treat it as a backreference.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="InternalBackRefs"><title>Regex Back-Reference Availability</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>One important thing here has to be remembered: Whenever you

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess use parentheses in <em>Pattern</em> or in one of the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>CondPattern</em>, back-references are internally created

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess which can be used with the strings <code>$N</code> and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>%N</code> (see below). These are available for creating

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the strings <em>Substitution</em> and <em>TestString</em>.

5a58787efeb02a1c3f06569d019ad81fd2efa06end Figure 2 shows to which locations the back-references are

5a58787efeb02a1c3f06569d019ad81fd2efa06end transfered for expansion.</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<p class="figure">

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <img src="/images/mod_rewrite_fig2.gif" width="381"

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess height="179" alt="[Needs graphics capability to display]" /><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dfn>Figure 2:</dfn> The back-reference flow through a rule.

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>We know this was a crash course on mod_rewrite's internal

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess processing. But you will benefit from this knowledge when

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess reading the following documentation of the available

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess directives.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<section id="EnvVar"><title>Environment Variables</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This module keeps track of two additional (non-standard)

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess CGI/SSI environment variables named <code>SCRIPT_URL</code>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess and <code>SCRIPT_URI</code>. These contain the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>logical</em> Web-view to the current resource, while the

261c62b53a9c707c64c7824eed68b5463bd23e62nd standard CGI/SSI variables <code>SCRIPT_NAME</code> and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>SCRIPT_FILENAME</code> contain the <em>physical</em>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess System-view. </p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Notice: These variables hold the URI/URL <em>as they were

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess initially requested</em>, <em>i.e.</em>, <em>before</em> any

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rewriting. This is important because the rewriting process is

261c62b53a9c707c64c7824eed68b5463bd23e62nd primarily used to rewrite logical URLs to physical

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess pathnames.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example><title>Example</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessSCRIPT_NAME=/sw/lib/w3s/tree/global/u/rse/.www/index.html

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessSCRIPT_FILENAME=/u/rse/.www/index.html

261c62b53a9c707c64c7824eed68b5463bd23e62ndSCRIPT_URL=/u/rse/

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessSCRIPT_URI=http://en1.engelschall.com/u/rse/

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</section>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

261c62b53a9c707c64c7824eed68b5463bd23e62nd<section id="Solutions"><title>Practical Solutions</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>We also have an <a href="/misc/rewriteguide.html">URL

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Rewriting Guide</a> available, which provides a collection of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess practical solutions for URL-based problems. There you can

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess find real-life rulesets and additional information about

5a58787efeb02a1c3f06569d019ad81fd2efa06end mod_rewrite.</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end</section>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<name>RewriteEngine</name>

261c62b53a9c707c64c7824eed68b5463bd23e62nd<description>Enables or disables runtime rewriting engine</description>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<syntax>RewriteEngine on|off</syntax>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<default>RewriteEngine off</default>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<contextlist><context>server config</context><context>virtual host</context>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<context>directory</context><context>.htaccess</context></contextlist>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<override>FileInfo</override>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <directive>RewriteEngine</directive> directive enables or

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess disables the runtime rewriting engine. If it is set to

261c62b53a9c707c64c7824eed68b5463bd23e62nd <code>off</code> this module does no runtime processing at

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess all. It does not even update the <code>SCRIPT_URx</code>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess environment variables.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Use this directive to disable the module instead of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess commenting out all the <directive

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess module="mod_rewrite">RewriteRule</directive> directives!</p>

261c62b53a9c707c64c7824eed68b5463bd23e62nd

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Note that, by default, rewrite configurations are not

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess inherited. This means that you need to have a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>RewriteEngine on</code> directive for each virtual host

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess in which you wish to use it.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<directivesynopsis>

5a58787efeb02a1c3f06569d019ad81fd2efa06end<name>RewriteOptions</name>

5a58787efeb02a1c3f06569d019ad81fd2efa06end<description>Sets some special options for the rewrite engine</description>

5a58787efeb02a1c3f06569d019ad81fd2efa06end<syntax>RewriteOptions <var>Options</var></syntax>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<default>RewriteOptions MaxRedirects=10</default>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<contextlist><context>server config</context><context>virtual host</context>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<context>directory</context><context>.htaccess</context></contextlist>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<override>FileInfo</override>

261c62b53a9c707c64c7824eed68b5463bd23e62nd<compatibility><code>MaxRedirects</code> is available in Apache 2.0.45 and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kesslater</compatibility>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <directive>RewriteOptions</directive> directive sets some

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess special options for the current per-server or per-directory

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess configuration. The <em>Option</em> strings can be one of the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess following:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dl>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dt><code>inherit</code></dt>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dd>This forces the current configuration to inherit the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess configuration of the parent. In per-virtual-server context

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess this means that the maps, conditions and rules of the main

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess server are inherited. In per-directory context this means

261c62b53a9c707c64c7824eed68b5463bd23e62nd that conditions and rules of the parent directory's

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>.htaccess</code> configuration are inherited.</dd>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dt><code>MaxRedirects=<var>number</var></code></dt>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <dd>In order to prevent endless loops of internal redirects

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess issued by per-directory <directive module="mod_rewrite"

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess >RewriteRule</directive>s, <module>mod_rewrite</module> aborts

261c62b53a9c707c64c7824eed68b5463bd23e62nd the request after reaching a maximum number of such redirects and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess responds with an 500 Internal Server Error. If you really need

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess more internal redirects than 10 per request, you may increase

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the default to the desired value.</dd>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </dl>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

261c62b53a9c707c64c7824eed68b5463bd23e62nd</directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<name>RewriteLog</name>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<description>Sets the name of the file used for logging rewrite engine

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessprocessing</description>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<syntax>RewriteLog <em>file-path</em></syntax>

261c62b53a9c707c64c7824eed68b5463bd23e62nd<contextlist><context>server config</context><context>virtual host</context>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</contextlist>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <directive>RewriteLog</directive> directive sets the name

5a58787efeb02a1c3f06569d019ad81fd2efa06end of the file to which the server logs any rewriting actions it

5a58787efeb02a1c3f06569d019ad81fd2efa06end performs. If the name does not begin with a slash

5a58787efeb02a1c3f06569d019ad81fd2efa06end ('<code>/</code>') then it is assumed to be relative to the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Server Root</em>. The directive should occur only once per

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess server config.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<note> To disable the logging of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rewriting actions it is not recommended to set

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Filename</em> to <code>/dev/null</code>, because

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess although the rewriting engine does not then output to a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess logfile it still creates the logfile output internally.

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong>This will slow down the server with no advantage

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess to the administrator!</strong> To disable logging either

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess remove or comment out the <directive>RewriteLog</directive>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess directive or use <code>RewriteLogLevel 0</code>!

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</note>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<note type="securitywarning"><title>Security</title>

261c62b53a9c707c64c7824eed68b5463bd23e62nd

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessSee the <a href="/misc/security_tips.html">Apache Security Tips</a>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessdocument for details on why your security could be compromised if the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessdirectory where logfiles are stored is writable by anyone other than

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessthe user that starts the server.

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</note>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

261c62b53a9c707c64c7824eed68b5463bd23e62nd<example><title>Example</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessRewriteLog "/usr/local/var/apache/logs/rewrite.log"

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<name>RewriteLogLevel</name>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<description>Sets the verbosity of the log file used by the rewrite

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessengine</description>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<syntax>RewriteLogLevel <em>Level</em></syntax>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<default>RewriteLogLevel 0</default>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<contextlist><context>server config</context><context>virtual host</context>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</contextlist>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <directive>RewriteLogLevel</directive> directive sets the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess verbosity level of the rewriting logfile. The default level 0

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess means no logging, while 9 or more means that practically all

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess actions are logged.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>To disable the logging of rewriting actions simply set

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Level</em> to 0. This disables all rewrite action

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess logs.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

5a58787efeb02a1c3f06569d019ad81fd2efa06end<note> Using a high value for

5a58787efeb02a1c3f06569d019ad81fd2efa06end <em>Level</em> will slow down your Apache server

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen dramatically! Use the rewriting logfile at a

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen <em>Level</em> greater than 2 only for debugging!

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen</note>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<example><title>Example</title>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowenRewriteLogLevel 3

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen</example>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen</usage>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen</directivesynopsis>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<directivesynopsis>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<name>RewriteLock</name>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<description>Sets the name of the lock file used for <directive

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowenmodule="mod_rewrite">RewriteMap</directive>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowensynchronization</description>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<syntax>RewriteLock <em>file-path</em></syntax>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<contextlist><context>server config</context></contextlist>

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen

f8dee27891059abb09ff5ca3fc5434f5719d22a0rbowen<usage>

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p>This directive sets the filename for a synchronization

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess lockfile which mod_rewrite needs to communicate with <directive

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess module="mod_rewrite">RewriteMap</directive>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>programs</em>. Set this lockfile to a local path (not on a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess NFS-mounted device) when you want to use a rewriting

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess map-program. It is not required for other types of rewriting

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess maps.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<directivesynopsis>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<name>RewriteMap</name>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<description>Defines a mapping function for key-lookup</description>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<syntax>RewriteMap <em>MapName</em> <em>MapType</em>:<em>MapSource</em>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</syntax>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<contextlist><context>server config</context><context>virtual host</context>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</contextlist>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<compatibility>The choice of different dbm types is available in

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessApache 2.0.41 and later</compatibility>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<usage>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <directive>RewriteMap</directive> directive defines a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>Rewriting Map</em> which can be used inside rule

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess substitution strings by the mapping-functions to

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess insert/substitute fields through a key lookup. The source of

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess this lookup can be of various types.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The <a id="mapfunc" name="mapfunc"><em>MapName</em></a> is

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the name of the map and will be used to specify a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess mapping-function for the substitution strings of a rewriting

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess rule via one of the following constructs:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p class="indent">

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong><code>${</code> <em>MapName</em> <code>:</code>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>LookupKey</em> <code>}</code><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>${</code> <em>MapName</em> <code>:</code>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>LookupKey</em> <code>|</code> <em>DefaultValue</em>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>}</code></strong>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>When such a construct occurs the map <em>MapName</em> is

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess consulted and the key <em>LookupKey</em> is looked-up. If the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess key is found, the map-function construct is substituted by

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>SubstValue</em>. If the key is not found then it is

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess substituted by <em>DefaultValue</em> or by the empty string

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess if no <em>DefaultValue</em> was specified.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>The following combinations for <em>MapType</em> and

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>MapSource</em> can be used:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <ul>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong>Standard Plain Text</strong><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess MapType: <code>txt</code>, MapSource: Unix filesystem

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess path to valid regular file

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This is the standard rewriting map feature where the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>MapSource</em> is a plain ASCII file containing

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess either blank lines, comment lines (starting with a '#'

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess character) or pairs like the following - one per

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess line.</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p class="indent">

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong><em>MatchingKey</em>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <em>SubstValue</em></strong>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example><title>Example</title>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess## map.txt -- rewriting map

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessRalf.S.Engelschall rse # Bastard Operator From Hell

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessMr.Joe.Average joe # Mr. Average

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example>

d5b8072762cf428c4c703ed7054ae948d41c910bndRewriteMap real-to-user txt:/path/to/file/map.txt

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

5a58787efeb02a1c3f06569d019ad81fd2efa06end <li>

5a58787efeb02a1c3f06569d019ad81fd2efa06end <strong>Randomized Plain Text</strong><br />

5a58787efeb02a1c3f06569d019ad81fd2efa06end MapType: <code>rnd</code>, MapSource: Unix filesystem

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess path to valid regular file

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>This is identical to the Standard Plain Text variant

261c62b53a9c707c64c7824eed68b5463bd23e62nd above but with a special post-processing feature: After

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess looking up a value it is parsed according to contained

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess ``<code>|</code>'' characters which have the meaning of

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd ``or''. In other words they indicate a set of

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd alternatives from which the actual returned value is

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd chosen randomly. Although this sounds crazy and useless,

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess it was actually designed for load balancing in a reverse

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess proxy situation where the looked up values are server

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess names. Example:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess## map.txt -- rewriting map

261c62b53a9c707c64c7824eed68b5463bd23e62nd##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessstatic www1|www2|www3|www4

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessdynamic www5|www6

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example>

261c62b53a9c707c64c7824eed68b5463bd23e62ndRewriteMap servers rnd:/path/to/file/map.txt

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong>Hash File</strong><br /> MapType:

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <code>dbm[=<em>type</em>]</code>, MapSource: Unix filesystem

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess path to valid regular file

261c62b53a9c707c64c7824eed68b5463bd23e62nd

261c62b53a9c707c64c7824eed68b5463bd23e62nd <p>Here the source is a binary format DBM file containing

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess the same contents as a <em>Plain Text</em> format file, but

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess in a special representation which is optimized for really

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess fast lookups. The <em>type</em> can be sdbm, gdbm, ndbm, or

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess db depending on <a href="/install.html#dbm">compile-time

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess settings</a>. If the <em>type</em> is omitted, the

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess compile-time default will be chosen. You can create such a

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess file with any DBM tool or with the following Perl

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess script. Be sure to adjust it to create the appropriate

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess type of DBM. The example creates an NDBM file.</p>

5a58787efeb02a1c3f06569d019ad81fd2efa06end

5a58787efeb02a1c3f06569d019ad81fd2efa06end<example>

5a58787efeb02a1c3f06569d019ad81fd2efa06end<pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess#!/path/to/bin/perl

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess## txt2dbm -- convert txt map to dbm format

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess##

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessuse NDBM_File;

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessuse Fcntl;

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess($txtmap, $dbmmap) = @ARGV;

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessopen(TXT, "&lt;$txtmap") or die "Couldn't open $txtmap!\n";

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kesstie (%DB, 'NDBM_File', $dbmmap,O_RDWR|O_TRUNC|O_CREAT, 0644)

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess or die "Couldn't create $dbmmap!\n";

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kesswhile (&lt;TXT&gt;) {

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess next if (/^\s*#/ or /^\s*$/);

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess $DB{$1} = $2 if (/^\s*(\S+)\s+(\S+)/);

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess}

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessuntie %DB;

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kessclose(TXT);

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</pre>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess<example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess$ txt2dbm map.txt map.db

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess</example>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <strong>Internal Function</strong><br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess MapType: <code>int</code>, MapSource: Internal Apache

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess function

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <p>Here the source is an internal Apache function.

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Currently you cannot create your own, but the following

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess functions already exists:</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <ul>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li><strong>toupper</strong>:<br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Converts the looked up key to all upper case.</li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li><strong>tolower</strong>:<br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Converts the looked up key to all lower case.</li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li><strong>escape</strong>:<br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Translates special characters in the looked up key to

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess hex-encodings.</li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li><strong>unescape</strong>:<br />

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess Translates hex-encodings in the looked up key back to

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess special characters.</li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </ul>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess </li>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess <li>

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd <strong>External Rewriting Program</strong><br />

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd MapType: <code>prg</code>, MapSource: Unix filesystem

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd path to valid regular file

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd <p>Here the source is a program, not a map file. To

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd create it you can use the language of your choice, but

a795ca2487c774aa6fe75c765a2bf17f969f7af7nd the result has to be a executable (<em>i.e.</em>, either

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess object-code or a script with the magic cookie trick

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess '<code>#!/path/to/interpreter</code>' as the first

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess line).</p>

fefb8b844b6286bfc41bb2e0c4cc003b8e7d4ff2kess

5a58787efeb02a1c3f06569d019ad81fd2efa06end <p>This program is started once at startup of the Apache

3b3b7fc78d1f5bfc2769903375050048ff41ff26nd servers and then communicates with the rewriting engine

ad74a0524a06bfe11b7de9e3b4ce7233ab3bd3f7nd over its <code>stdin</code> and <code>stdout</code>

d05d0eb4ae6d2a5e513fc3bf2555ce33da416634nd file-handles. For each map-function lookup it will

7f5b59ccc63c0c0e3e678a168f09ee6a2f51f9d0nd receive the key to lookup as a newline-terminated string

7f5b59ccc63c0c0e3e678a168f09ee6a2f51f9d0nd on <code>stdin</code>. It then has to give back the

3b3b7fc78d1f5bfc2769903375050048ff41ff26nd looked-up value as a newline-terminated string on

4b22542f6f38567cae7873b176188a6622f67eb0fielding <code>stdout</code> or the four-character string

5a58787efeb02a1c3f06569d019ad81fd2efa06end ``<code>NULL</code>'' if it fails (<em>i.e.</em>, there

5a58787efeb02a1c3f06569d019ad81fd2efa06end 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), because

if this program hangs it will hang the Apache server

when the rule occurs.</li>

<li>Avoid one common mistake: never do buffered I/O on

<code>stdout</code>! This will cause a deadloop! Hence

the ``<code>$|=1</code>'' in the above example...</li>

<li>Use the <directive

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

define a lockfile mod_rewrite can use to synchronize the

communication to the 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>). There it will act locally,

<em>i.e.</em>, the local directory prefix is stripped at this

stage of processing and your rewriting rules act only on the

remainder. At the end it 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>But at most websites URLs are NOT

directly related to physical filename paths, so this

assumption will usually be wrong!</strong> There you have to

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 have to use

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

files 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

the correct Apache internal processing, because the

per-directory rewriting comes too late in the

process. So, when it occurs the (rewritten) request

has to be re-injected into the Apache kernel! BUT:

While this seems like a serious overhead, it really

isn't, because this re-injection happens fully

internally to the Apache server and the same

procedure is used by many other operations inside

Apache. So, you can be sure the design and

implementation is correct.</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. Precede a <directive

module="mod_rewrite">RewriteRule</directive> directive with one

or more <directive>RewriteCond</directive> directives. The following

rewriting rule is only used if its pattern matches the current

state of the URI <strong>and</strong> if these additional

conditions apply too.</p>

<p><em>TestString</em> is a string which can contains the

following expanded constructs in addition to plain text:</p>

<ul>

<li>

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

backreferences of the form

<p class="indent">

<strong><code>$N</code></strong>

</p>

(0 &lt;= N &lt;= 9) which provide access to the grouped

parts (parenthesis!) of the pattern from the

corresponding <code>RewriteRule</code> directive (the one

following the current bunch of <code>RewriteCond</code>

directives).

</li>

<li>

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

backreferences of the form

<p class="indent">

<strong><code>%N</code></strong>

</p>

(1 &lt;= N &lt;= 9) which provide access to the grouped

parts (parentheses!) of the pattern from the last matched

<code>RewriteCond</code> directive in the current bunch

of conditions.

</li>

<li>

<strong>RewriteMap expansions</strong>: These are

expansions of the form

<p class="indent">

<strong><code>${mapname:key|default}</code></strong>

</p>

See <a href="#mapfunc">the documentation for

RewriteMap</a> for more details.

</li>

<li>

<strong>Server-Variables</strong>: These are variables of

the form

<p class="indent">

<strong><code>%{</code> <em>NAME_OF_VARIABLE</em>

<code>}</code></strong>

</p>

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>system stuff:</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>

<note>

<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:</p>

<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

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

</dl>

</note>

</li>

</ul>

<p>Special Notes:</p>

<ol>

<li>The variables SCRIPT_FILENAME and REQUEST_FILENAME

contain the same value, <em>i.e.</em>, the value of the

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

<code>request_rec</code> structure of the Apache server.

The first name is just the commonly known CGI variable name

while the second is the consistent counterpart to

REQUEST_URI (which contains the value of the

<code>uri</code> field of <code>request_rec</code>).</li>

<li>There is the special format:

<code>%{ENV:variable}</code> where <em>variable</em> can be

any environment variable. This is looked-up via internal

Apache structures and (if not found there) via

<code>getenv()</code> from the Apache server process.</li>

<li>There is the special format:

<code>%{SSL:variable}</code> where <em>variable</em> is the

name of an <a href="mod_ssl.html#envvars">SSL environment

variable</a>; this 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>There is the special format:

<code>%{HTTP:header}</code> where <em>header</em> can be

any HTTP MIME-header name. This is looked-up from the HTTP

request. Example: <code>%{HTTP:Proxy-Connection}</code> is

the value of the HTTP header

``<code>Proxy-Connection:</code>''.</li>

<li>There is the special format

<code>%{LA-U:variable}</code> for look-aheads which perform

an internal (URL-based) sub-request to determine the final

value of <em>variable</em>. Use this when you want to use a

variable for rewriting which is actually set later in an

API phase and thus is not available at the current stage.

For instance when you want to rewrite according to the

<code>REMOTE_USER</code> variable from within the

per-server context (<code>httpd.conf</code> file) you have

to use <code>%{LA-U:REMOTE_USER}</code> because this

variable is set by the authorization phases which come

<em>after</em> the URL translation phase where mod_rewrite

operates. 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> there.</li>

<li>There is the special format:

<code>%{LA-F:variable}</code> which performs 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,

<em>i.e.</em>, a regular expression which is applied to the

current instance of the <em>TestString</em>, <em>i.e.</em>,

<em>TestString</em> is evaluated and then 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>' (is lexically

lower)<br />

Treats the <em>CondPattern</em> as a plain string and

compares it lexically to <em>TestString</em>. True if

<em>TestString</em> is lexically lower than

<em>CondPattern</em>.</li>

<li>'<strong>&gt;CondPattern</strong>' (is lexically

greater)<br />

Treats the <em>CondPattern</em> as a plain string and

compares it lexically to <em>TestString</em>. True if

<em>TestString</em> is lexically greater than

<em>CondPattern</em>.</li>

<li>'<strong>=CondPattern</strong>' (is lexically

equal)<br />

Treats the <em>CondPattern</em> as a plain string and

compares it lexically to <em>TestString</em>. True if

<em>TestString</em> is lexically equal to

<em>CondPattern</em>, i.e the two strings are exactly

equal (character by character). If <em>CondPattern</em>

is just <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

if 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

if 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

if 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

if 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

if it exists and has execution permissions. These permissions

are determined depending on the underlying OS.</li>

<li>'<strong>-F</strong>' (is existing file via

subrequest)<br />

Checks if <em>TestString</em> is a valid file and

accessible via all the server's currently-configured

access controls for that path. This uses an internal

subrequest to determine the check, so use it with care

because it decreases your servers performance!</li>

<li>'<strong>-U</strong>' (is existing URL via

subrequest)<br />

Checks if <em>TestString</em> is a valid URL and

accessible via all the server's currently-configured

access controls for that path. This uses an internal

subrequest to determine the check, so use it with care

because it decreases your server's performance!</li>

</ul>

<note><title>Notice</title>

All of these tests can

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

negate their meaning.

</note>

</li>

</ol>

<p>Additionally you can set special flags for

<em>CondPattern</em> by appending</p>

<p class="indent">

<strong><code>[</code><em>flags</em><code>]</code></strong>

</p>

<p>as the third argument to the <code>RewriteCond</code>

directive. <em>Flags</em> is a comma-separated list of the

following flags:</p>

<ul>

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

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

This makes the test case-insensitive, <em>i.e.</em>, there

is no difference between 'A-Z' and 'a-z' 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 cond/rule

three times.

</li>

</ul>

<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>Interpretation: If you use Netscape Navigator as your

browser (which identifies itself as 'Mozilla'), then you

get the max homepage, which includes Frames, <em>etc.</em>

If you use the Lynx browser (which is Terminal-based), then

you get the min homepage, which contains no images, no

tables, <em>etc.</em> If you use any other browser you get

the 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.

Each directive then defines one single rewriting rule. The

<strong>definition order</strong> of these rules is

<strong>important</strong>, because this order is used when

applying the rules 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 gets applied to the current URL. Here

``current'' means the value of the URL when this rule gets

applied. This may not be the originally requested URL,

because any number of rules may already have matched and made

alterations to it.</p>

<p>Some hints about the syntax of regular expressions:</p>

<note><pre>

<strong>Text:</strong>

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

<strong><code>[</code></strong>chars<strong><code>]</code></strong> Character class: One of chars

<strong><code>[^</code></strong>chars<strong><code>]</code></strong> Character class: None of chars

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

<strong>Quantifiers:</strong>

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

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

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

<strong>Grouping:</strong>

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

(either to set the borders of an alternative or

for making backreferences where the <strong>N</strong>th group can

be used on the RHS of a RewriteRule with <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 that particular 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 <em>etc.</em>) have a look at the

following dedicated book on this topic:</p>

<p class="indent">

<em>Mastering Regular Expressions</em><br />

Jeffrey E.F. Friedl<br />

Nutshell Handbook Series<br />

O'Reilly &amp; Associates, Inc. 1997<br />

ISBN 1-56592-257-3<br />

</p>

<p>Additionally in mod_rewrite the NOT character

('<code>!</code>') is a possible pattern prefix. This gives

you the ability 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>Notice</title>

When using the NOT character

to negate a pattern you cannot have grouped wildcard

parts in the pattern. This is impossible because when the

pattern does NOT match, there are no contents for the

groups. In consequence, if negated patterns are used, you

cannot use <code>$N</code> in the substitution

string!

</note>

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

rewriting rule is the string which is substituted for (or

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

matched. Beside plain text you can use</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 <code>$</code><strong>N</strong>

(<strong>N</strong>=0..9) identifiers 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 of

the above list. </p>

<p>As already mentioned above, all the rewriting rules are

applied to the <em>Substitution</em> (in the order of

definition in the config file). The URL is <strong>completely

replaced</strong> by the <em>Substitution</em> and the

rewriting process goes on until there are no more rules

unless explicitly terminated by a

<code><strong>L</strong></code> flag - see below.</p>

<p>There is a special substitution string named

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

substitution</strong>! Sounds silly? No, it is useful to

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

some URLs but do no substitution, <em>e.g.</em>, in

conjunction with the <strong>C</strong> (chain) flag to be

able to have more than one pattern to be applied before a

substitution occurs.</p>

<note><title>Query String</title>

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

Instead, 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. Just use a question mark inside the substitution string to

indicate that the following stuff should be re-injected into the

query string. When you want to erase an existing query string,

end the substitution string with just the question mark. To

combine a new query string with an old one, use the

<code>[QSA]</code> flag (see below).</p>

</note>

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

<p>There is a special feature:

When you prefix a substitution field with

<code>http://</code><em>thishost</em>[<em>:thisport</em>]

then <strong>mod_rewrite</strong> automatically strips it

out. This auto-reduction on implicit external redirect

URLs is a useful and important feature when used in

combination with a mapping-function which generates the

hostname part. Have a look at the first example in the

example section below to understand this.</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 (see below).</p>

</note>

<p>Additionally you can set special flags for

<em>Substitution</em> by appending</p>

<p class="indent">

<strong><code>[</code><em>flags</em><code>]</code></strong>

</p>

<p>

as the third argument to the <code>RewriteRule</code>

directive. <em>Flags</em> is a comma-separated list of the

following flags: </p>

<ul>

<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) is used. If you want to use other response

codes in the range 300-400 just specify them as a number

or use one of the following symbolic names:

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

<code>seeother</code>. Use it for rules which should

canonicalize the URL and give it back to the client,

<em>e.g.</em>, translate ``<code>/~</code>'' into

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

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

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

sure that the substitution field is a valid URL! If not,

you are redirecting to an invalid location! And remember

that this flag itself only prefixes the URL with

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

continues. Usually you also want to stop and do the

redirection immediately. To stop the rewriting you also

have to provide the 'L' flag.</p>

</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,

<em>i.e.</em>, 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, <em>i.e.</em>, 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>proxy|P</code></strong>' (force

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

This flag forces the substitution part to be internally

forced as a proxy request and immediately (<em>i.e.</em>,

rewriting rule processing stops here) put through the <a

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

sure that the substitution string is a valid URI

(<em>e.g.</em>, typically starting with

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

handled by the Apache proxy module. If not you 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 some remote stuff into the namespace of the local

server.

<p>Notice: To use this functionality make sure you have

the proxy module compiled into your Apache server

program. If you don't know please check whether

<code>mod_proxy.c</code> is part of the ``<code>httpd

-l</code>'' output. If yes, this functionality is

available to mod_rewrite. If not, then you first have to

rebuild the ``<code>httpd</code>'' program with mod_proxy

enabled.</p>

</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

rewriting rules. This corresponds to the Perl

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

from the C language. 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>,