--- /dev/null
+URI: index.html.en
+Content-Language: en
+Content-type: text/html; charset=ISO-8859-1
--- /dev/null
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>Apache mod_rewrite - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="../"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Apache mod_rewrite</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/rewrite/" title="English"> en </a></p>
+</div>
+
+ <blockquote>
+ <p>``The great thing about mod_rewrite is it gives you
+ all the configurability and flexibility of Sendmail.
+ The downside to mod_rewrite is that it gives you all
+ the configurability and flexibility of Sendmail.''</p>
+
+ <p class="cite">-- <cite>Brian Behlendorf</cite><br />
+ Apache Group</p>
+
+ </blockquote>
+
+ <blockquote>
+ <p>`` Despite the tons of examples and docs,
+ mod_rewrite is voodoo. Damned cool voodoo, but still
+ voodoo. ''</p>
+
+ <p class="cite">-- <cite>Brian Moore</cite><br />
+ bem@news.cmc.net</p>
+
+ </blockquote>
+
+ <p>Welcome to mod_rewrite, the Swiss Army Knife of URL
+ manipulation!</p>
+
+ <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,
+ for instance server variables, environment variables, HTTP
+ headers, time stamps and even external database lookups in
+ various formats can be used to achieve 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 even 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>But all this functionality and flexibility has its
+ drawback: complexity. So don't expect to understand this
+ entire module in just one day.</p>
+
+</div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#documentation">Documentation</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#mod-rewrite">mod_rewrite</a></li>
+</ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="documentation" id="documentation">Documentation</a></h2>
+<ul>
+<li><a href="rewrite_intro.html">Introduction</a></li>
+<li><a href="rewrite_tech.html">Technical details</a></li>
+<li><a href="rewrite_guide.html">Practical solutions to common
+problems</a></li>
+<li><a href="../glossary.html">Glossary</a></li>
+</ul>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="mod-rewrite" id="mod-rewrite">mod_rewrite</a></h2>
+<p>Extensive documentation on the directives
+provided by this module is provided in the <a href="../mod/mod_rewrite.html">mod_rewrite reference documentation</a>.
+</p>
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/rewrite/" title="English"> en </a></p>
+</div><div id="footer">
+<p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html>
\ No newline at end of file
--- /dev/null
+<?xml version='1.0' encoding='UTF-8' ?>
+<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
+<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
+<!-- $LastChangedRevision$ -->
+
+<!--
+ Copyright 2002-2005 The Apache Software Foundation or its licensors, as
+ applicable.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<manualpage metafile="index.xml.meta">
+<parentdocument href="../"/>
+
+ <title>Apache mod_rewrite</title>
+
+<summary>
+ <blockquote>
+ <p>``The great thing about mod_rewrite is it gives you
+ all the configurability and flexibility of Sendmail.
+ The downside to mod_rewrite is that it gives you all
+ the configurability and flexibility of Sendmail.''</p>
+
+ <p class="cite">-- <cite>Brian Behlendorf</cite><br />
+ Apache Group</p>
+
+ </blockquote>
+
+ <blockquote>
+ <p>`` Despite the tons of examples and docs,
+ mod_rewrite is voodoo. Damned cool voodoo, but still
+ voodoo. ''</p>
+
+ <p class="cite">-- <cite>Brian Moore</cite><br />
+ bem@news.cmc.net</p>
+
+ </blockquote>
+
+ <p>Welcome to mod_rewrite, the Swiss Army Knife of URL
+ manipulation!</p>
+
+ <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,
+ for instance server variables, environment variables, HTTP
+ headers, time stamps and even external database lookups in
+ various formats can be used to achieve 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 even 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>But all this functionality and flexibility has its
+ drawback: complexity. So don't expect to understand this
+ entire module in just one day.</p>
+
+</summary>
+
+<section id="documentation"><title>Documentation</title>
+<ul>
+<li><a href="../mod/mod_rewrite.html">mod_rewrite reference
+documentation</a></li>
+<li><a href="rewrite_intro.html">Introduction</a></li>
+<li><a href="rewrite_tech.html">Technical details</a></li>
+<li><a href="rewrite_guide.html">Practical solutions to common
+problems</a></li>
+<li><a href="../glossary.html">Glossary</a></li>
+</ul>
+</section>
+
+</manualpage>
+
+
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<metafile>
+ <basename>index</basename>
+ <path>/rewrite/</path>
+ <relpath>..</relpath>
+
+ <variants>
+ <variant>en</variant>
+ </variants>
+</metafile>
--- /dev/null
+URI: rewrite_guide.html.en
+Content-Language: en
+Content-type: text/html; charset=ISO-8859-1
--- /dev/null
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>URL Rewriting Guide - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./index.html"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>URL Rewriting Guide</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_guide.html" title="English"> en </a></p>
+</div>
+
+
+ <p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ <a href="../mod/mod_rewrite.html">reference documentation</a>.
+ It describes how one can use Apache's <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ to solve typical URL-based problems with which webmasters are
+ commonony confronted. We give detailed descriptions on how to
+ solve each problem by configuring URL rewriting rulesets.</p>
+
+ <div class="warning">ATTENTION: Depending on your server configuration
+ it may be necessary to slightly change the examples for your
+ situation, e.g. adding the <code>[PT]</code> flag when
+ additionally using <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> and
+ <code class="module"><a href="../mod/mod_userdir.html">mod_userdir</a></code>, etc. Or rewriting a ruleset
+ to fit in <code>.htaccess</code> context instead
+ of per-server context. Always try to understand what a
+ particular ruleset really does before you use it. This
+ avoids many problems.</div>
+
+ </div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#canonicalurl">Canonical URLs</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#canonicalhost">Canonical Hostnames</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#moveddocroot">Moved <code>DocumentRoot</code></a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#trailingslash">Trailing Slash Problem</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#movehomedirs">Move Homedirs to Different Webserver</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#multipledirs">Search pages in more than one directory</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#setenvvars">Set Environment Variables According To URL Parts</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#uservhosts">Virtual User Hosts</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#redirecthome">Redirect Homedirs For Foreigners</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#redirectanchors">Redirecting Anchors</a></li>
+<li><img alt="" src="../images/down.gif" /> Time-Dependent Rewriting</li>
+<li><img alt="" src="../images/down.gif" /> Backward Compatibility for YYYY to XXXX migration</li>
+<li><img alt="" src="../images/down.gif" /> <a href="#content">Content Handling</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#access">Access Restriction</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#other">Other</a></li>
+</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module
+documentation</a></li><li><a href="rewrite_intro.html">mod_rewrite
+introduction</a></li><li><a href="rewrite_tech.html">Technical details</a></li></ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="canonicalurl" id="canonicalurl">Canonical URLs</a></h2>
+
+
+
+<dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>On some webservers there are more than one URL for a
+ resource. Usually there are canonical URLs (which should be
+ actually used and distributed) and those which are just
+ shortcuts, internal ones, etc. Independent of which URL the
+ user supplied with the request he should finally see the
+ canonical one only.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We do an external HTTP redirect for all non-canonical
+ URLs to fix them in the location view of the Browser and
+ for all subsequent requests. In the example ruleset below
+ we replace <code>/~user</code> by the canonical
+ <code>/u/user</code> and fix a missing trailing slash for
+ <code>/u/user</code>.</p>
+
+<div class="example"><pre>
+RewriteRule ^/<strong>~</strong>([^/]+)/?(.*) /<strong>u</strong>/$1/$2 [<strong>R</strong>]
+RewriteRule ^/([uge])/(<strong>[^/]+</strong>)$ /$1/$2<strong>/</strong> [<strong>R</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="canonicalhost" id="canonicalhost">Canonical Hostnames</a></h2>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>The goal of this rule is to force the use of a particular
+ hostname, in preference to other hostnames which may be used to
+ reach the same site. For example, if you wish to force the use
+ of <strong>www.example.com</strong> instead of
+ <strong>example.com</strong>, you might use a variant of the
+ following recipe.</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+<p>For sites running on a port other than 80:</p>
+<div class="example"><pre>
+RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC]
+RewriteCond %{HTTP_HOST} !^$
+RewriteCond %{SERVER_PORT} !^80$
+RewriteRule ^/(.*) http://fully.qualified.domain.name:%{SERVER_PORT}/$1 [L,R]
+</pre></div>
+
+<p>And for a site running on port 80</p>
+<div class="example"><pre>
+RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC]
+RewriteCond %{HTTP_HOST} !^$
+RewriteRule ^/(.*) http://fully.qualified.domain.name/$1 [L,R]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="moveddocroot" id="moveddocroot">Moved <code>DocumentRoot</code></a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+<p>Usually the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
+of the webserver directly relates to the URL "<code>/</code>".
+But often this data is not really of top-level priority. For example,
+you may wish for visitors, on first entering a site, to go to a
+particular subdirectory <code>/about/</code>. This may be accomplished
+using the following ruleset:</p>
+</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We redirect the URL <code>/</code> to
+ <code>/about/</code>:
+ </p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteRule <strong>^/$</strong> /about/ [<strong>R</strong>]
+</pre></div>
+
+ <p>Note that this can also be handled using the <code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directive:</p>
+
+<div class="example"><p><code>
+RedirectMatch ^/$ http://example.com/e/www/
+</code></p></div>
+</dd>
+</dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="trailingslash" id="trailingslash">Trailing Slash Problem</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd><p>The vast majority of "trailing slash" problems can be dealt
+ with using the techniques discussed in the <a href="http://httpd.apache.org/docs/misc/FAQ-E.html#set-servername">FAQ
+ entry</a>. However, occasionally, there is a need to use mod_rewrite
+ to handle a case where a missing trailing slash causes a URL to
+ fail. This can happen, for example, after a series of complex
+ rewrite rules.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution to this subtle problem is to let the server
+ add the trailing slash automatically. To do this
+ correctly we have to use an external redirect, so the
+ browser correctly requests subsequent images etc. If we
+ only did a internal rewrite, this would only work for the
+ directory page, but would go wrong when any images are
+ included into this page with relative URLs, because the
+ browser would request an in-lined object. For instance, a
+ request for <code>image.gif</code> in
+ <code>/~quux/foo/index.html</code> would become
+ <code>/~quux/image.gif</code> without the external
+ redirect!</p>
+
+ <p>So, to do this trick we write:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^foo<strong>$</strong> foo<strong>/</strong> [<strong>R</strong>]
+</pre></div>
+
+ <p>Alternately, you can put the following in a
+ top-level <code>.htaccess</code> file in the content directory.
+ But note that this creates some processing overhead.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteCond %{REQUEST_FILENAME} <strong>-d</strong>
+RewriteRule ^(.+<strong>[^/]</strong>)$ $1<strong>/</strong> [R]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="movehomedirs" id="movehomedirs">Move Homedirs to Different Webserver</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Many webmasters have asked for a solution to the
+ following situation: They wanted to redirect just all
+ homedirs on a webserver to another webserver. They usually
+ need such things when establishing a newer webserver which
+ will replace the old one over time.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution is trivial with <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.
+ On the old webserver we just redirect all
+ <code>/~user/anypath</code> URLs to
+ <code>http://newserver/~user/anypath</code>.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteRule ^/~(.+) http://<strong>newserver</strong>/~$1 [R,L]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="multipledirs" id="multipledirs">Search pages in more than one directory</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Sometimes it is necessary to let the webserver search
+ for pages in more than one directory. Here MultiViews or
+ other techniques cannot help.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We program a explicit ruleset which searches for the
+ files in the directories.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+
+# first try to find it in custom/...
+# ...and if found stop and be happy:
+RewriteCond /your/docroot/<strong>dir1</strong>/%{REQUEST_FILENAME} -f
+RewriteRule ^(.+) /your/docroot/<strong>dir1</strong>/$1 [L]
+
+# second try to find it in pub/...
+# ...and if found stop and be happy:
+RewriteCond /your/docroot/<strong>dir2</strong>/%{REQUEST_FILENAME} -f
+RewriteRule ^(.+) /your/docroot/<strong>dir2</strong>/$1 [L]
+
+# else go on for other Alias or ScriptAlias directives,
+# etc.
+RewriteRule ^(.+) - [PT]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="setenvvars" id="setenvvars">Set Environment Variables According To URL Parts</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Perhaps you want to keep status information between
+ requests and use the URL to encode it. But you don't want
+ to use a CGI wrapper for all pages just to strip out this
+ information.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a rewrite rule to strip out the status information
+ and remember it via an environment variable which can be
+ later dereferenced from within XSSI or CGI. This way a
+ URL <code>/foo/S=java/bar/</code> gets translated to
+ <code>/foo/bar/</code> and the environment variable named
+ <code>STATUS</code> is set to the value "java".</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteRule ^(.*)/<strong>S=([^/]+)</strong>/(.*) $1/$3 [E=<strong>STATUS:$2</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="uservhosts" id="uservhosts">Virtual User Hosts</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume that you want to provide
+ <code>www.<strong>username</strong>.host.domain.com</code>
+ for the homepage of username via just DNS A records to the
+ same machine and without any virtualhosts on this
+ machine.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>For HTTP/1.0 requests there is no solution, but for
+ HTTP/1.1 requests which contain a Host: HTTP header we
+ can use the following ruleset to rewrite
+ <code>http://www.username.host.com/anypath</code>
+ internally to <code>/home/username/anypath</code>:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond %{<strong>HTTP_HOST</strong>} ^www\.<strong>[^.]+</strong>\.host\.com$
+RewriteRule ^(.+) %{HTTP_HOST}$1 [C]
+RewriteRule ^www\.<strong>([^.]+)</strong>\.host\.com(.*) /home/<strong>$1</strong>$2
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="redirecthome" id="redirecthome">Redirect Homedirs For Foreigners</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>We want to redirect homedir URLs to another webserver
+ <code>www.somewhere.com</code> when the requesting user
+ does not stay in the local domain
+ <code>ourdomain.com</code>. This is sometimes used in
+ virtual host contexts.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Just a rewrite condition:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond %{REMOTE_HOST} <strong>!^.+\.ourdomain\.com$</strong>
+RewriteRule ^(/~.+) http://www.somewhere.com/$1 [R,L]
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="redirectanchors" id="redirectanchors">Redirecting Anchors</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>By default, redirecting to an HTML anchor doesn't work,
+ because mod_rewrite escapes the <code>#</code> character,
+ turning it into <code>%23</code>. This, in turn, breaks the
+ redirection.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use the <code>[NE]</code> flag on the
+ <code>RewriteRule</code>. NE stands for No Escape.
+ </p>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2>Time-Dependent Rewriting</h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>When tricks like time-dependent content should happen a
+ lot of webmasters still use CGI scripts which do for
+ instance redirects to specialized pages. How can it be done
+ via <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>There are a lot of variables named <code>TIME_xxx</code>
+ for rewrite conditions. In conjunction with the special
+ lexicographic comparison patterns <code><STRING</code>,
+ <code>>STRING</code> and <code>=STRING</code> we can
+ do time-dependent redirects:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700
+RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900
+RewriteRule ^foo\.html$ foo.day.html
+RewriteRule ^foo\.html$ foo.night.html
+</pre></div>
+
+ <p>This provides the content of <code>foo.day.html</code>
+ under the URL <code>foo.html</code> from
+ <code>07:00-19:00</code> and at the remaining time the
+ contents of <code>foo.night.html</code>. Just a nice
+ feature for a homepage...</p>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2>Backward Compatibility for YYYY to XXXX migration</h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we make URLs backward compatible (still
+ existing virtually) after migrating <code>document.YYYY</code>
+ to <code>document.XXXX</code>, e.g. after translating a
+ bunch of <code>.html</code> files to <code>.phtml</code>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We just rewrite the name to its basename and test for
+ existence of the new extension. If it exists, we take
+ that name, else we rewrite the URL to its original state.</p>
+
+
+<div class="example"><pre>
+# backward compatibility ruleset for
+# rewriting document.html to document.phtml
+# when and only when document.phtml exists
+# but no longer document.html
+RewriteEngine on
+RewriteBase /~quux/
+# parse out basename, but remember the fact
+RewriteRule ^(.*)\.html$ $1 [C,E=WasHTML:yes]
+# rewrite to document.phtml if exists
+RewriteCond %{REQUEST_FILENAME}.phtml -f
+RewriteRule ^(.*)$ $1.phtml [S=1]
+# else reverse the previous basename cutout
+RewriteCond %{ENV:WasHTML} ^yes$
+RewriteRule ^(.*)$ $1.html
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="content" id="content">Content Handling</a></h2>
+
+
+
+ <h3>From Old to New (intern)</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume we have recently renamed the page
+ <code>foo.html</code> to <code>bar.html</code> and now want
+ to provide the old URL for backward compatibility. Actually
+ we want that users of the old URL even not recognize that
+ the pages was renamed.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We rewrite the old URL to the new one internally via the
+ following rule:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>foo</strong>\.html$ <strong>bar</strong>.html
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>From Old to New (extern)</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume again that we have recently renamed the page
+ <code>foo.html</code> to <code>bar.html</code> and now want
+ to provide the old URL for backward compatibility. But this
+ time we want that the users of the old URL get hinted to
+ the new one, i.e. their browsers Location field should
+ change, too.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We force a HTTP redirect to the new URL which leads to a
+ change of the browsers and thus the users view:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>foo</strong>\.html$ <strong>bar</strong>.html [<strong>R</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>From Static to Dynamic</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we transform a static page
+ <code>foo.html</code> into a dynamic variant
+ <code>foo.cgi</code> in a seamless way, i.e. without notice
+ by the browser/user.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We just rewrite the URL to the CGI-script and force the
+ correct MIME-type so it gets really run as a CGI-script.
+ This way a request to <code>/~quux/foo.html</code>
+ internally leads to the invocation of
+ <code>/~quux/foo.cgi</code>.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^foo\.<strong>html</strong>$ foo.<strong>cgi</strong> [T=<strong>application/x-httpd-cgi</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="access" id="access">Access Restriction</a></h2>
+
+
+
+ <h3>Blocking of Robots</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we block a really annoying robot from
+ retrieving pages of a specific webarea? A
+ <code>/robots.txt</code> file containing entries of the
+ "Robot Exclusion Protocol" is typically not enough to get
+ rid of such a robot.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a ruleset which forbids the URLs of the webarea
+ <code>/~quux/foo/arc/</code> (perhaps a very deep
+ directory indexed area where the robot traversal would
+ create big server load). We have to make sure that we
+ forbid access only to the particular robot, i.e. just
+ forbidding the host where the robot runs is not enough.
+ This would block users from this host, too. We accomplish
+ this by also matching the User-Agent HTTP header
+ information.</p>
+
+<div class="example"><pre>
+RewriteCond %{HTTP_USER_AGENT} ^<strong>NameOfBadRobot</strong>.*
+RewriteCond %{REMOTE_ADDR} ^<strong>123\.45\.67\.[8-9]</strong>$
+RewriteRule ^<strong>/~quux/foo/arc/</strong>.+ - [<strong>F</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Blocked Inline-Images</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume we have under <code>http://www.quux-corp.de/~quux/</code>
+ some pages with inlined GIF graphics. These graphics are
+ nice, so others directly incorporate them via hyperlinks to
+ their pages. We don't like this practice because it adds
+ useless traffic to our server.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>While we cannot 100% protect the images from inclusion,
+ we can at least restrict the cases where the browser
+ sends a HTTP Referer header.</p>
+
+<div class="example"><pre>
+RewriteCond %{HTTP_REFERER} <strong>!^$</strong>
+RewriteCond %{HTTP_REFERER} !^http://www.quux-corp.de/~quux/.*$ [NC]
+RewriteRule <strong>.*\.gif$</strong> - [F]
+</pre></div>
+
+<div class="example"><pre>
+RewriteCond %{HTTP_REFERER} !^$
+RewriteCond %{HTTP_REFERER} !.*/foo-with-gif\.html$
+RewriteRule <strong>^inlined-in-foo\.gif$</strong> - [F]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Proxy Deny</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a certain host or even a user of a
+ special host from using the Apache proxy?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We first have to make sure <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ is below(!) <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> in the Configuration
+ file when compiling the Apache webserver. This way it gets
+ called <em>before</em> <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. Then we
+ configure the following for a host-dependent deny...</p>
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_HOST} <strong>^badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></div>
+
+ <p>...and this one for a user@host-dependent deny:</p>
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>^badguy@badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="other" id="other">Other</a></h2>
+
+
+
+ <h3>External Rewriting Engine</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>A FAQ: How can we solve the FOO/BAR/QUUX/etc.
+ problem? There seems no solution by the use of
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>...</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use an external <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code>, i.e. a program which acts
+ like a <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code>. It is run once on startup of Apache
+ receives the requested URLs on <code>STDIN</code> and has
+ to put the resulting (usually rewritten) URL on
+ <code>STDOUT</code> (same order!).</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteMap quux-map <strong>prg:</strong>/path/to/map.quux.pl
+RewriteRule ^/~quux/(.*)$ /~quux/<strong>${quux-map:$1}</strong>
+</pre></div>
+
+<div class="example"><pre>
+#!/path/to/perl
+
+# disable buffered I/O which would lead
+# to deadloops for the Apache server
+$| = 1;
+
+# read URLs one per line from stdin and
+# generate substitution URL on stdout
+while (<>) {
+ s|^foo/|bar/|;
+ print $_;
+}
+</pre></div>
+
+ <p>This is a demonstration-only example and just rewrites
+ all URLs <code>/~quux/foo/...</code> to
+ <code>/~quux/bar/...</code>. Actually you can program
+ whatever you like. But notice that while such maps can be
+ <strong>used</strong> also by an average user, only the
+ system administrator can <strong>define</strong> it.</p>
+ </dd>
+ </dl>
+
+
+
+ </div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_guide.html" title="English"> en </a></p>
+</div><div id="footer">
+<p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html>
\ No newline at end of file
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
+<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
+<!-- $LastChangedRevision: 123578 $ -->
+
+<!--
+ Copyright 2002-2005 The Apache Software Foundation or its licensors, as
+ applicable.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<manualpage metafile="rewrite_guide.xml.meta">
+ <parentdocument href="./index.html" />
+
+ <title>URL Rewriting Guide</title>
+
+ <summary>
+
+ <p>This document supplements the <module>mod_rewrite</module>
+ <a href="../mod/mod_rewrite.html">reference documentation</a>.
+ It describes how one can use Apache's <module>mod_rewrite</module>
+ to solve typical URL-based problems with which webmasters are
+ commonony confronted. We give detailed descriptions on how to
+ solve each problem by configuring URL rewriting rulesets.</p>
+
+ <note type="warning">ATTENTION: Depending on your server configuration
+ it may be necessary to slightly change the examples for your
+ situation, e.g. adding the <code>[PT]</code> flag when
+ additionally using <module>mod_alias</module> and
+ <module>mod_userdir</module>, etc. Or rewriting a ruleset
+ to fit in <code>.htaccess</code> context instead
+ of per-server context. Always try to understand what a
+ particular ruleset really does before you use it. This
+ avoids many problems.</note>
+
+ </summary>
+<seealso><a href="../mod/mod_rewrite.html">Module
+documentation</a></seealso>
+<seealso><a href="rewrite_intro.html">mod_rewrite
+introduction</a></seealso>
+<seealso><a href="rewrite_tech.html">Technical details</a></seealso>
+
+
+<section id="canonicalurl">
+
+<title>Canonical URLs</title>
+
+<dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>On some webservers there are more than one URL for a
+ resource. Usually there are canonical URLs (which should be
+ actually used and distributed) and those which are just
+ shortcuts, internal ones, etc. Independent of which URL the
+ user supplied with the request he should finally see the
+ canonical one only.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We do an external HTTP redirect for all non-canonical
+ URLs to fix them in the location view of the Browser and
+ for all subsequent requests. In the example ruleset below
+ we replace <code>/~user</code> by the canonical
+ <code>/u/user</code> and fix a missing trailing slash for
+ <code>/u/user</code>.</p>
+
+<example><pre>
+RewriteRule ^/<strong>~</strong>([^/]+)/?(.*) /<strong>u</strong>/$1/$2 [<strong>R</strong>]
+RewriteRule ^/([uge])/(<strong>[^/]+</strong>)$ /$1/$2<strong>/</strong> [<strong>R</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+<section id="canonicalhost"><title>Canonical Hostnames</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>The goal of this rule is to force the use of a particular
+ hostname, in preference to other hostnames which may be used to
+ reach the same site. For example, if you wish to force the use
+ of <strong>www.example.com</strong> instead of
+ <strong>example.com</strong>, you might use a variant of the
+ following recipe.</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+<p>For sites running on a port other than 80:</p>
+<example><pre>
+RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC]
+RewriteCond %{HTTP_HOST} !^$
+RewriteCond %{SERVER_PORT} !^80$
+RewriteRule ^/(.*) http://fully.qualified.domain.name:%{SERVER_PORT}/$1 [L,R]
+</pre></example>
+
+<p>And for a site running on port 80</p>
+<example><pre>
+RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC]
+RewriteCond %{HTTP_HOST} !^$
+RewriteRule ^/(.*) http://fully.qualified.domain.name/$1 [L,R]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="moveddocroot">
+
+ <title>Moved <code>DocumentRoot</code></title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+<p>Usually the <directive module="core">DocumentRoot</directive>
+of the webserver directly relates to the URL "<code>/</code>".
+But often this data is not really of top-level priority. For example,
+you may wish for visitors, on first entering a site, to go to a
+particular subdirectory <code>/about/</code>. This may be accomplished
+using the following ruleset:</p>
+</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We redirect the URL <code>/</code> to
+ <code>/about/</code>:
+ </p>
+
+<example><pre>
+RewriteEngine on
+RewriteRule <strong>^/$</strong> /about/ [<strong>R</strong>]
+</pre></example>
+
+ <p>Note that this can also be handled using the <directive
+ module="mod_alias">RedirectMatch</directive> directive:</p>
+
+<example>
+RedirectMatch ^/$ http://example.com/e/www/
+</example>
+</dd>
+</dl>
+
+ </section>
+
+ <section id="trailingslash">
+
+ <title>Trailing Slash Problem</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd><p>The vast majority of "trailing slash" problems can be dealt
+ with using the techniques discussed in the <a
+ href="http://httpd.apache.org/docs/misc/FAQ-E.html#set-servername">FAQ
+ entry</a>. However, occasionally, there is a need to use mod_rewrite
+ to handle a case where a missing trailing slash causes a URL to
+ fail. This can happen, for example, after a series of complex
+ rewrite rules.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution to this subtle problem is to let the server
+ add the trailing slash automatically. To do this
+ correctly we have to use an external redirect, so the
+ browser correctly requests subsequent images etc. If we
+ only did a internal rewrite, this would only work for the
+ directory page, but would go wrong when any images are
+ included into this page with relative URLs, because the
+ browser would request an in-lined object. For instance, a
+ request for <code>image.gif</code> in
+ <code>/~quux/foo/index.html</code> would become
+ <code>/~quux/image.gif</code> without the external
+ redirect!</p>
+
+ <p>So, to do this trick we write:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^foo<strong>$</strong> foo<strong>/</strong> [<strong>R</strong>]
+</pre></example>
+
+ <p>Alternately, you can put the following in a
+ top-level <code>.htaccess</code> file in the content directory.
+ But note that this creates some processing overhead.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteCond %{REQUEST_FILENAME} <strong>-d</strong>
+RewriteRule ^(.+<strong>[^/]</strong>)$ $1<strong>/</strong> [R]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="movehomedirs">
+
+ <title>Move Homedirs to Different Webserver</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Many webmasters have asked for a solution to the
+ following situation: They wanted to redirect just all
+ homedirs on a webserver to another webserver. They usually
+ need such things when establishing a newer webserver which
+ will replace the old one over time.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution is trivial with <module>mod_rewrite</module>.
+ On the old webserver we just redirect all
+ <code>/~user/anypath</code> URLs to
+ <code>http://newserver/~user/anypath</code>.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteRule ^/~(.+) http://<strong>newserver</strong>/~$1 [R,L]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="multipledirs">
+
+ <title>Search pages in more than one directory</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Sometimes it is necessary to let the webserver search
+ for pages in more than one directory. Here MultiViews or
+ other techniques cannot help.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We program a explicit ruleset which searches for the
+ files in the directories.</p>
+
+<example><pre>
+RewriteEngine on
+
+# first try to find it in custom/...
+# ...and if found stop and be happy:
+RewriteCond /your/docroot/<strong>dir1</strong>/%{REQUEST_FILENAME} -f
+RewriteRule ^(.+) /your/docroot/<strong>dir1</strong>/$1 [L]
+
+# second try to find it in pub/...
+# ...and if found stop and be happy:
+RewriteCond /your/docroot/<strong>dir2</strong>/%{REQUEST_FILENAME} -f
+RewriteRule ^(.+) /your/docroot/<strong>dir2</strong>/$1 [L]
+
+# else go on for other Alias or ScriptAlias directives,
+# etc.
+RewriteRule ^(.+) - [PT]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="setenvvars">
+
+ <title>Set Environment Variables According To URL Parts</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Perhaps you want to keep status information between
+ requests and use the URL to encode it. But you don't want
+ to use a CGI wrapper for all pages just to strip out this
+ information.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a rewrite rule to strip out the status information
+ and remember it via an environment variable which can be
+ later dereferenced from within XSSI or CGI. This way a
+ URL <code>/foo/S=java/bar/</code> gets translated to
+ <code>/foo/bar/</code> and the environment variable named
+ <code>STATUS</code> is set to the value "java".</p>
+
+<example><pre>
+RewriteEngine on
+RewriteRule ^(.*)/<strong>S=([^/]+)</strong>/(.*) $1/$3 [E=<strong>STATUS:$2</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="uservhosts">
+
+ <title>Virtual User Hosts</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume that you want to provide
+ <code>www.<strong>username</strong>.host.domain.com</code>
+ for the homepage of username via just DNS A records to the
+ same machine and without any virtualhosts on this
+ machine.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>For HTTP/1.0 requests there is no solution, but for
+ HTTP/1.1 requests which contain a Host: HTTP header we
+ can use the following ruleset to rewrite
+ <code>http://www.username.host.com/anypath</code>
+ internally to <code>/home/username/anypath</code>:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteCond %{<strong>HTTP_HOST</strong>} ^www\.<strong>[^.]+</strong>\.host\.com$
+RewriteRule ^(.+) %{HTTP_HOST}$1 [C]
+RewriteRule ^www\.<strong>([^.]+)</strong>\.host\.com(.*) /home/<strong>$1</strong>$2
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="redirecthome">
+
+ <title>Redirect Homedirs For Foreigners</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>We want to redirect homedir URLs to another webserver
+ <code>www.somewhere.com</code> when the requesting user
+ does not stay in the local domain
+ <code>ourdomain.com</code>. This is sometimes used in
+ virtual host contexts.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Just a rewrite condition:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteCond %{REMOTE_HOST} <strong>!^.+\.ourdomain\.com$</strong>
+RewriteRule ^(/~.+) http://www.somewhere.com/$1 [R,L]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="redirectanchors">
+
+ <title>Redirecting Anchors</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>By default, redirecting to an HTML anchor doesn't work,
+ because mod_rewrite escapes the <code>#</code> character,
+ turning it into <code>%23</code>. This, in turn, breaks the
+ redirection.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use the <code>[NE]</code> flag on the
+ <code>RewriteRule</code>. NE stands for No Escape.
+ </p>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Time-Dependent Rewriting</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>When tricks like time-dependent content should happen a
+ lot of webmasters still use CGI scripts which do for
+ instance redirects to specialized pages. How can it be done
+ via <module>mod_rewrite</module>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>There are a lot of variables named <code>TIME_xxx</code>
+ for rewrite conditions. In conjunction with the special
+ lexicographic comparison patterns <code><STRING</code>,
+ <code>>STRING</code> and <code>=STRING</code> we can
+ do time-dependent redirects:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700
+RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900
+RewriteRule ^foo\.html$ foo.day.html
+RewriteRule ^foo\.html$ foo.night.html
+</pre></example>
+
+ <p>This provides the content of <code>foo.day.html</code>
+ under the URL <code>foo.html</code> from
+ <code>07:00-19:00</code> and at the remaining time the
+ contents of <code>foo.night.html</code>. Just a nice
+ feature for a homepage...</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Backward Compatibility for YYYY to XXXX migration</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we make URLs backward compatible (still
+ existing virtually) after migrating <code>document.YYYY</code>
+ to <code>document.XXXX</code>, e.g. after translating a
+ bunch of <code>.html</code> files to <code>.phtml</code>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We just rewrite the name to its basename and test for
+ existence of the new extension. If it exists, we take
+ that name, else we rewrite the URL to its original state.</p>
+
+
+<example><pre>
+# backward compatibility ruleset for
+# rewriting document.html to document.phtml
+# when and only when document.phtml exists
+# but no longer document.html
+RewriteEngine on
+RewriteBase /~quux/
+# parse out basename, but remember the fact
+RewriteRule ^(.*)\.html$ $1 [C,E=WasHTML:yes]
+# rewrite to document.phtml if exists
+RewriteCond %{REQUEST_FILENAME}.phtml -f
+RewriteRule ^(.*)$ $1.phtml [S=1]
+# else reverse the previous basename cutout
+RewriteCond %{ENV:WasHTML} ^yes$
+RewriteRule ^(.*)$ $1.html
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="content">
+
+ <title>Content Handling</title>
+
+ <section>
+
+ <title>From Old to New (intern)</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume we have recently renamed the page
+ <code>foo.html</code> to <code>bar.html</code> and now want
+ to provide the old URL for backward compatibility. Actually
+ we want that users of the old URL even not recognize that
+ the pages was renamed.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We rewrite the old URL to the new one internally via the
+ following rule:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>foo</strong>\.html$ <strong>bar</strong>.html
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>From Old to New (extern)</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume again that we have recently renamed the page
+ <code>foo.html</code> to <code>bar.html</code> and now want
+ to provide the old URL for backward compatibility. But this
+ time we want that the users of the old URL get hinted to
+ the new one, i.e. their browsers Location field should
+ change, too.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We force a HTTP redirect to the new URL which leads to a
+ change of the browsers and thus the users view:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>foo</strong>\.html$ <strong>bar</strong>.html [<strong>R</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>From Static to Dynamic</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we transform a static page
+ <code>foo.html</code> into a dynamic variant
+ <code>foo.cgi</code> in a seamless way, i.e. without notice
+ by the browser/user.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We just rewrite the URL to the CGI-script and force the
+ correct MIME-type so it gets really run as a CGI-script.
+ This way a request to <code>/~quux/foo.html</code>
+ internally leads to the invocation of
+ <code>/~quux/foo.cgi</code>.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^foo\.<strong>html</strong>$ foo.<strong>cgi</strong> [T=<strong>application/x-httpd-cgi</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+</section>
+
+ <section id="access">
+
+ <title>Access Restriction</title>
+
+ <section>
+
+ <title>Blocking of Robots</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we block a really annoying robot from
+ retrieving pages of a specific webarea? A
+ <code>/robots.txt</code> file containing entries of the
+ "Robot Exclusion Protocol" is typically not enough to get
+ rid of such a robot.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a ruleset which forbids the URLs of the webarea
+ <code>/~quux/foo/arc/</code> (perhaps a very deep
+ directory indexed area where the robot traversal would
+ create big server load). We have to make sure that we
+ forbid access only to the particular robot, i.e. just
+ forbidding the host where the robot runs is not enough.
+ This would block users from this host, too. We accomplish
+ this by also matching the User-Agent HTTP header
+ information.</p>
+
+<example><pre>
+RewriteCond %{HTTP_USER_AGENT} ^<strong>NameOfBadRobot</strong>.*
+RewriteCond %{REMOTE_ADDR} ^<strong>123\.45\.67\.[8-9]</strong>$
+RewriteRule ^<strong>/~quux/foo/arc/</strong>.+ - [<strong>F</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Blocked Inline-Images</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume we have under <code>http://www.quux-corp.de/~quux/</code>
+ some pages with inlined GIF graphics. These graphics are
+ nice, so others directly incorporate them via hyperlinks to
+ their pages. We don't like this practice because it adds
+ useless traffic to our server.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>While we cannot 100% protect the images from inclusion,
+ we can at least restrict the cases where the browser
+ sends a HTTP Referer header.</p>
+
+<example><pre>
+RewriteCond %{HTTP_REFERER} <strong>!^$</strong>
+RewriteCond %{HTTP_REFERER} !^http://www.quux-corp.de/~quux/.*$ [NC]
+RewriteRule <strong>.*\.gif$</strong> - [F]
+</pre></example>
+
+<example><pre>
+RewriteCond %{HTTP_REFERER} !^$
+RewriteCond %{HTTP_REFERER} !.*/foo-with-gif\.html$
+RewriteRule <strong>^inlined-in-foo\.gif$</strong> - [F]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Proxy Deny</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a certain host or even a user of a
+ special host from using the Apache proxy?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We first have to make sure <module>mod_rewrite</module>
+ is below(!) <module>mod_proxy</module> in the Configuration
+ file when compiling the Apache webserver. This way it gets
+ called <em>before</em> <module>mod_proxy</module>. Then we
+ configure the following for a host-dependent deny...</p>
+
+<example><pre>
+RewriteCond %{REMOTE_HOST} <strong>^badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></example>
+
+ <p>...and this one for a user@host-dependent deny:</p>
+
+<example><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>^badguy@badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ </section>
+
+ <section id="other">
+
+ <title>Other</title>
+
+ <section>
+
+ <title>External Rewriting Engine</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>A FAQ: How can we solve the FOO/BAR/QUUX/etc.
+ problem? There seems no solution by the use of
+ <module>mod_rewrite</module>...</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use an external <directive module="mod_rewrite"
+ >RewriteMap</directive>, i.e. a program which acts
+ like a <directive module="mod_rewrite"
+ >RewriteMap</directive>. It is run once on startup of Apache
+ receives the requested URLs on <code>STDIN</code> and has
+ to put the resulting (usually rewritten) URL on
+ <code>STDOUT</code> (same order!).</p>
+
+<example><pre>
+RewriteEngine on
+RewriteMap quux-map <strong>prg:</strong>/path/to/map.quux.pl
+RewriteRule ^/~quux/(.*)$ /~quux/<strong>${quux-map:$1}</strong>
+</pre></example>
+
+<example><pre>
+#!/path/to/perl
+
+# disable buffered I/O which would lead
+# to deadloops for the Apache server
+$| = 1;
+
+# read URLs one per line from stdin and
+# generate substitution URL on stdout
+while (<>) {
+ s|^foo/|bar/|;
+ print $_;
+}
+</pre></example>
+
+ <p>This is a demonstration-only example and just rewrites
+ all URLs <code>/~quux/foo/...</code> to
+ <code>/~quux/bar/...</code>. Actually you can program
+ whatever you like. But notice that while such maps can be
+ <strong>used</strong> also by an average user, only the
+ system administrator can <strong>define</strong> it.</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ </section>
+
+</manualpage>
+
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<metafile>
+ <basename>rewrite_guide</basename>
+ <path>/rewrite/</path>
+ <relpath>..</relpath>
+
+ <variants>
+ <variant>en</variant>
+ </variants>
+</metafile>
--- /dev/null
+URI: rewrite_guide_advanced.html.en
+Content-Language: en
+Content-type: text/html; charset=ISO-8859-1
--- /dev/null
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>URL Rewriting Guide - Advanced topics - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./index.html"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>URL Rewriting Guide - Advanced topics</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_guide_advanced.html" title="English"> en </a></p>
+</div>
+
+
+ <p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ <a href="../mod/mod_rewrite.html">reference documentation</a>.
+ It describes how one can use Apache's <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ to solve typical URL-based problems with which webmasters are
+ commonony confronted. We give detailed descriptions on how to
+ solve each problem by configuring URL rewriting rulesets.</p>
+
+ <div class="warning">ATTENTION: Depending on your server configuration
+ it may be necessary to slightly change the examples for your
+ situation, e.g. adding the <code>[PT]</code> flag when
+ additionally using <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> and
+ <code class="module"><a href="../mod/mod_userdir.html">mod_userdir</a></code>, etc. Or rewriting a ruleset
+ to fit in <code>.htaccess</code> context instead
+ of per-server context. Always try to understand what a
+ particular ruleset really does before you use it. This
+ avoids many problems.</div>
+
+ </div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#cluster">Webcluster through Homogeneous URL Layout</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#structuredhomedirs">Structured Homedirs</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#filereorg">Filesystem Reorganization</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#redirect404">Redirect Failing URLs To Other Webserver</a></li>
+<li><img alt="" src="../images/down.gif" /> Archive Access Multiplexer</li>
+<li><img alt="" src="../images/down.gif" /> <a href="#content">Content Handling</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#access">Access Restriction</a></li>
+</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module
+documentation</a></li><li><a href="rewrite_intro.html">mod_rewrite
+introduction</a></li><li><a href="rewrite_tech.html">Technical details</a></li></ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="cluster" id="cluster">Webcluster through Homogeneous URL Layout</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>We want to create a homogeneous and consistent URL
+ layout over all WWW servers on a Intranet webcluster, i.e.
+ all URLs (per definition server local and thus server
+ dependent!) become actually server <em>independent</em>!
+ What we want is to give the WWW namespace a consistent
+ server-independent layout: no URL should have to include
+ any physically correct target server. The cluster itself
+ should drive us automatically to the physical target
+ host.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First, the knowledge of the target servers come from
+ (distributed) external maps which contain information
+ where our users, groups and entities stay. The have the
+ form</p>
+
+<div class="example"><pre>
+user1 server_of_user1
+user2 server_of_user2
+: :
+</pre></div>
+
+ <p>We put them into files <code>map.xxx-to-host</code>.
+ Second we need to instruct all servers to redirect URLs
+ of the forms</p>
+
+<div class="example"><pre>
+/u/user/anypath
+/g/group/anypath
+/e/entity/anypath
+</pre></div>
+
+ <p>to</p>
+
+<div class="example"><pre>
+http://physical-host/u/user/anypath
+http://physical-host/g/group/anypath
+http://physical-host/e/entity/anypath
+</pre></div>
+
+ <p>when the URL is not locally valid to a server. The
+ following ruleset does this for us by the help of the map
+ files (assuming that server0 is a default server which
+ will be used if a user has no entry in the map):</p>
+
+<div class="example"><pre>
+RewriteEngine on
+
+RewriteMap user-to-host txt:/path/to/map.user-to-host
+RewriteMap group-to-host txt:/path/to/map.group-to-host
+RewriteMap entity-to-host txt:/path/to/map.entity-to-host
+
+RewriteRule ^/u/<strong>([^/]+)</strong>/?(.*) http://<strong>${user-to-host:$1|server0}</strong>/u/$1/$2
+RewriteRule ^/g/<strong>([^/]+)</strong>/?(.*) http://<strong>${group-to-host:$1|server0}</strong>/g/$1/$2
+RewriteRule ^/e/<strong>([^/]+)</strong>/?(.*) http://<strong>${entity-to-host:$1|server0}</strong>/e/$1/$2
+
+RewriteRule ^/([uge])/([^/]+)/?$ /$1/$2/.www/
+RewriteRule ^/([uge])/([^/]+)/([^.]+.+) /$1/$2/.www/$3\
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="structuredhomedirs" id="structuredhomedirs">Structured Homedirs</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Some sites with thousands of users usually use a
+ structured homedir layout, i.e. each homedir is in a
+ subdirectory which begins for instance with the first
+ character of the username. So, <code>/~foo/anypath</code>
+ is <code>/home/<strong>f</strong>/foo/.www/anypath</code>
+ while <code>/~bar/anypath</code> is
+ <code>/home/<strong>b</strong>/bar/.www/anypath</code>.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use the following ruleset to expand the tilde URLs
+ into exactly the above layout.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteRule ^/~(<strong>([a-z])</strong>[a-z0-9]+)(.*) /home/<strong>$2</strong>/$1/.www$3
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="filereorg" id="filereorg">Filesystem Reorganization</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>This really is a hardcore example: a killer application
+ which heavily uses per-directory
+ <code>RewriteRules</code> to get a smooth look and feel
+ on the Web while its data structure is never touched or
+ adjusted. Background: <strong><em>net.sw</em></strong> is
+ my archive of freely available Unix software packages,
+ which I started to collect in 1992. It is both my hobby
+ and job to to this, because while I'm studying computer
+ science I have also worked for many years as a system and
+ network administrator in my spare time. Every week I need
+ some sort of software so I created a deep hierarchy of
+ directories where I stored the packages:</p>
+
+<div class="example"><pre>
+drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/
+drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/
+drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/
+drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/
+drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/
+drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/
+drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/
+drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/
+drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/
+drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/
+drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/
+drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/
+drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/
+drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/
+drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/
+drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/
+</pre></div>
+
+ <p>In July 1996 I decided to make this archive public to
+ the world via a nice Web interface. "Nice" means that I
+ wanted to offer an interface where you can browse
+ directly through the archive hierarchy. And "nice" means
+ that I didn't wanted to change anything inside this
+ hierarchy - not even by putting some CGI scripts at the
+ top of it. Why? Because the above structure should be
+ later accessible via FTP as well, and I didn't want any
+ Web or CGI stuff to be there.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution has two parts: The first is a set of CGI
+ scripts which create all the pages at all directory
+ levels on-the-fly. I put them under
+ <code>/e/netsw/.www/</code> as follows:</p>
+
+<div class="example"><pre>
+-rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl
+drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/
+-rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE
+-rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO
+-rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html
+-rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl
+-rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi
+-rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi
+drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/
+-rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi
+-rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi
+-rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi
+-rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst
+</pre></div>
+
+ <p>The <code>DATA/</code> subdirectory holds the above
+ directory structure, i.e. the real
+ <strong><em>net.sw</em></strong> stuff and gets
+ automatically updated via <code>rdist</code> from time to
+ time. The second part of the problem remains: how to link
+ these two structures together into one smooth-looking URL
+ tree? We want to hide the <code>DATA/</code> directory
+ from the user while running the appropriate CGI scripts
+ for the various URLs. Here is the solution: first I put
+ the following into the per-directory configuration file
+ in the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
+ of the server to rewrite the announced URL
+ <code>/net.sw/</code> to the internal path
+ <code>/e/netsw</code>:</p>
+
+<div class="example"><pre>
+RewriteRule ^net.sw$ net.sw/ [R]
+RewriteRule ^net.sw/(.*)$ e/netsw/$1
+</pre></div>
+
+ <p>The first rule is for requests which miss the trailing
+ slash! The second rule does the real thing. And then
+ comes the killer configuration which stays in the
+ per-directory config file
+ <code>/e/netsw/.www/.wwwacl</code>:</p>
+
+<div class="example"><pre>
+Options ExecCGI FollowSymLinks Includes MultiViews
+
+RewriteEngine on
+
+# we are reached via /net.sw/ prefix
+RewriteBase /net.sw/
+
+# first we rewrite the root dir to
+# the handling cgi script
+RewriteRule ^$ netsw-home.cgi [L]
+RewriteRule ^index\.html$ netsw-home.cgi [L]
+
+# strip out the subdirs when
+# the browser requests us from perdir pages
+RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L]
+
+# and now break the rewriting for local files
+RewriteRule ^netsw-home\.cgi.* - [L]
+RewriteRule ^netsw-changes\.cgi.* - [L]
+RewriteRule ^netsw-search\.cgi.* - [L]
+RewriteRule ^netsw-tree\.cgi$ - [L]
+RewriteRule ^netsw-about\.html$ - [L]
+RewriteRule ^netsw-img/.*$ - [L]
+
+# anything else is a subdir which gets handled
+# by another cgi script
+RewriteRule !^netsw-lsdir\.cgi.* - [C]
+RewriteRule (.*) netsw-lsdir.cgi/$1
+</pre></div>
+
+ <p>Some hints for interpretation:</p>
+
+ <ol>
+ <li>Notice the <code>L</code> (last) flag and no
+ substitution field ('<code>-</code>') in the forth part</li>
+
+ <li>Notice the <code>!</code> (not) character and
+ the <code>C</code> (chain) flag at the first rule
+ in the last part</li>
+
+ <li>Notice the catch-all pattern in the last rule</li>
+ </ol>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="redirect404" id="redirect404">Redirect Failing URLs To Other Webserver</a></h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>A typical FAQ about URL rewriting is how to redirect
+ failing requests on webserver A to webserver B. Usually
+ this is done via <code class="directive"><a href="../mod/core.html#errordocument">ErrorDocument</a></code> CGI-scripts in Perl, but
+ there is also a <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> solution.
+ But notice that this performs more poorly than using an
+ <code class="directive"><a href="../mod/core.html#errordocument">ErrorDocument</a></code>
+ CGI-script!</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The first solution has the best performance but less
+ flexibility, and is less error safe:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond /your/docroot/%{REQUEST_FILENAME} <strong>!-f</strong>
+RewriteRule ^(.+) http://<strong>webserverB</strong>.dom/$1
+</pre></div>
+
+ <p>The problem here is that this will only work for pages
+ inside the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>. While you can add more
+ Conditions (for instance to also handle homedirs, etc.)
+ there is better variant:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond %{REQUEST_URI} <strong>!-U</strong>
+RewriteRule ^(.+) http://<strong>webserverB</strong>.dom/$1
+</pre></div>
+
+ <p>This uses the URL look-ahead feature of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.
+ The result is that this will work for all types of URLs
+ and is a safe way. But it does a performance impact on
+ the webserver, because for every request there is one
+ more internal subrequest. So, if your webserver runs on a
+ powerful CPU, use this one. If it is a slow machine, use
+ the first approach or better a <code class="directive"><a href="../mod/core.html#errordocument">ErrorDocument</a></code> CGI-script.</p>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2>Archive Access Multiplexer</h2>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Do you know the great CPAN (Comprehensive Perl Archive
+ Network) under <a href="http://www.perl.com/CPAN">http://www.perl.com/CPAN</a>?
+ This does a redirect to one of several FTP servers around
+ the world which carry a CPAN mirror and is approximately
+ near the location of the requesting client. Actually this
+ can be called an FTP access multiplexing service. While
+ CPAN runs via CGI scripts, how can a similar approach
+ implemented via <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First we notice that from version 3.0.0
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> can
+ also use the "<code>ftp:</code>" scheme on redirects.
+ And second, the location approximation can be done by a
+ <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code>
+ over the top-level domain of the client.
+ With a tricky chained ruleset we can use this top-level
+ domain as a key to our multiplexing map.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteMap multiplex txt:/path/to/map.cxan
+RewriteRule ^/CxAN/(.*) %{REMOTE_HOST}::$1 [C]
+RewriteRule ^.+\.<strong>([a-zA-Z]+)</strong>::(.*)$ ${multiplex:<strong>$1</strong>|ftp.default.dom}$2 [R,L]
+</pre></div>
+
+<div class="example"><pre>
+##
+## map.cxan -- Multiplexing Map for CxAN
+##
+
+de ftp://ftp.cxan.de/CxAN/
+uk ftp://ftp.cxan.uk/CxAN/
+com ftp://ftp.cxan.com/CxAN/
+ :
+##EOF##
+</pre></div>
+ </dd>
+ </dl>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="content" id="content">Content Handling</a></h2>
+
+
+
+ <h3>Browser Dependent Content</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>At least for important top-level pages it is sometimes
+ necessary to provide the optimum of browser dependent
+ content, i.e. one has to provide a maximum version for the
+ latest Netscape variants, a minimum version for the Lynx
+ browsers and a average feature version for all others.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We cannot use content negotiation because the browsers do
+ not provide their type in that form. Instead we have to
+ act on the HTTP header "User-Agent". The following condig
+ does the following: If the HTTP header "User-Agent"
+ begins with "Mozilla/3", the page <code>foo.html</code>
+ is rewritten to <code>foo.NS.html</code> and and the
+ rewriting stops. If the browser is "Lynx" or "Mozilla" of
+ version 1 or 2 the URL becomes <code>foo.20.html</code>.
+ All other browsers receive page <code>foo.32.html</code>.
+ This is done by the following ruleset:</p>
+
+<div class="example"><pre>
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Mozilla/3</strong>.*
+RewriteRule ^foo\.html$ foo.<strong>NS</strong>.html [<strong>L</strong>]
+
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Lynx/</strong>.* [OR]
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Mozilla/[12]</strong>.*
+RewriteRule ^foo\.html$ foo.<strong>20</strong>.html [<strong>L</strong>]
+
+RewriteRule ^foo\.html$ foo.<strong>32</strong>.html [<strong>L</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Dynamic Mirror</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume there are nice webpages on remote hosts we want
+ to bring into our namespace. For FTP servers we would use
+ the <code>mirror</code> program which actually maintains an
+ explicit up-to-date copy of the remote data on the local
+ machine. For a webserver we could use the program
+ <code>webcopy</code> which acts similar via HTTP. But both
+ techniques have one major drawback: The local copy is
+ always just as up-to-date as often we run the program. It
+ would be much better if the mirror is not a static one we
+ have to establish explicitly. Instead we want a dynamic
+ mirror with data which gets updated automatically when
+ there is need (updated data on the remote host).</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>To provide this feature we map the remote webpage or even
+ the complete remote webarea to our namespace by the use
+ of the <dfn>Proxy Throughput</dfn> feature
+ (flag <code>[P]</code>):</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>hotsheet/</strong>(.*)$ <strong>http://www.tstimpreso.com/hotsheet/</strong>$1 [<strong>P</strong>]
+</pre></div>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>usa-news\.html</strong>$ <strong>http://www.quux-corp.com/news/index.html</strong> [<strong>P</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Reverse Dynamic Mirror</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>...</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+<div class="example"><pre>
+RewriteEngine on
+RewriteCond /mirror/of/remotesite/$1 -U
+RewriteRule ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Retrieve Missing Data from Intranet</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>This is a tricky way of virtually running a corporate
+ (external) Internet webserver
+ (<code>www.quux-corp.dom</code>), while actually keeping
+ and maintaining its data on a (internal) Intranet webserver
+ (<code>www2.quux-corp.dom</code>) which is protected by a
+ firewall. The trick is that on the external webserver we
+ retrieve the requested data on-the-fly from the internal
+ one.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First, we have to make sure that our firewall still
+ protects the internal webserver and that only the
+ external webserver is allowed to retrieve data from it.
+ For a packet-filtering firewall we could for instance
+ configure a firewall ruleset like the following:</p>
+
+<div class="example"><pre>
+<strong>ALLOW</strong> Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port <strong>80</strong>
+<strong>DENY</strong> Host * Port * --> Host www2.quux-corp.dom Port <strong>80</strong>
+</pre></div>
+
+ <p>Just adjust it to your actual configuration syntax.
+ Now we can establish the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ rules which request the missing data in the background
+ through the proxy throughput feature:</p>
+
+<div class="example"><pre>
+RewriteRule ^/~([^/]+)/?(.*) /home/$1/.www/$2
+RewriteCond %{REQUEST_FILENAME} <strong>!-f</strong>
+RewriteCond %{REQUEST_FILENAME} <strong>!-d</strong>
+RewriteRule ^/home/([^/]+)/.www/?(.*) http://<strong>www2</strong>.quux-corp.dom/~$1/pub/$2 [<strong>P</strong>]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Load Balancing</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Suppose we want to load balance the traffic to
+ <code>www.foo.com</code> over <code>www[0-5].foo.com</code>
+ (a total of 6 servers). How can this be done?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>There are a lot of possible solutions for this problem.
+ We will discuss first a commonly known DNS-based variant
+ and then the special one with <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>:</p>
+
+ <ol>
+ <li>
+ <strong>DNS Round-Robin</strong>
+
+ <p>The simplest method for load-balancing is to use
+ the DNS round-robin feature of <code>BIND</code>.
+ Here you just configure <code>www[0-9].foo.com</code>
+ as usual in your DNS with A(address) records, e.g.</p>
+
+<div class="example"><pre>
+www0 IN A 1.2.3.1
+www1 IN A 1.2.3.2
+www2 IN A 1.2.3.3
+www3 IN A 1.2.3.4
+www4 IN A 1.2.3.5
+www5 IN A 1.2.3.6
+</pre></div>
+
+ <p>Then you additionally add the following entry:</p>
+
+<div class="example"><pre>
+www IN CNAME www0.foo.com.
+ IN CNAME www1.foo.com.
+ IN CNAME www2.foo.com.
+ IN CNAME www3.foo.com.
+ IN CNAME www4.foo.com.
+ IN CNAME www5.foo.com.
+ IN CNAME www6.foo.com.
+</pre></div>
+
+ <p>Notice that this seems wrong, but is actually an
+ intended feature of <code>BIND</code> and can be used
+ in this way. However, now when <code>www.foo.com</code> gets
+ resolved, <code>BIND</code> gives out <code>www0-www6</code>
+ - but in a slightly permutated/rotated order every time.
+ This way the clients are spread over the various
+ servers. But notice that this not a perfect load
+ balancing scheme, because DNS resolve information
+ gets cached by the other nameservers on the net, so
+ once a client has resolved <code>www.foo.com</code>
+ to a particular <code>wwwN.foo.com</code>, all
+ subsequent requests also go to this particular name
+ <code>wwwN.foo.com</code>. But the final result is
+ ok, because the total sum of the requests are really
+ spread over the various webservers.</p>
+ </li>
+
+ <li>
+ <strong>DNS Load-Balancing</strong>
+
+ <p>A sophisticated DNS-based method for
+ load-balancing is to use the program
+ <code>lbnamed</code> which can be found at <a href="http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html">
+ http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html</a>.
+ It is a Perl 5 program in conjunction with auxilliary
+ tools which provides a real load-balancing for
+ DNS.</p>
+ </li>
+
+ <li>
+ <strong>Proxy Throughput Round-Robin</strong>
+
+ <p>In this variant we use <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ and its proxy throughput feature. First we dedicate
+ <code>www0.foo.com</code> to be actually
+ <code>www.foo.com</code> by using a single</p>
+
+<div class="example"><pre>
+www IN CNAME www0.foo.com.
+</pre></div>
+
+ <p>entry in the DNS. Then we convert
+ <code>www0.foo.com</code> to a proxy-only server,
+ i.e. we configure this machine so all arriving URLs
+ are just pushed through the internal proxy to one of
+ the 5 other servers (<code>www1-www5</code>). To
+ accomplish this we first establish a ruleset which
+ contacts a load balancing script <code>lb.pl</code>
+ for all URLs.</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteMap lb prg:/path/to/lb.pl
+RewriteRule ^/(.+)$ ${lb:$1} [P,L]
+</pre></div>
+
+ <p>Then we write <code>lb.pl</code>:</p>
+
+<div class="example"><pre>
+#!/path/to/perl
+##
+## lb.pl -- load balancing script
+##
+
+$| = 1;
+
+$name = "www"; # the hostname base
+$first = 1; # the first server (not 0 here, because 0 is myself)
+$last = 5; # the last server in the round-robin
+$domain = "foo.dom"; # the domainname
+
+$cnt = 0;
+while (<STDIN>) {
+ $cnt = (($cnt+1) % ($last+1-$first));
+ $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain);
+ print "http://$server/$_";
+}
+
+##EOF##
+</pre></div>
+
+ <div class="note">A last notice: Why is this useful? Seems like
+ <code>www0.foo.com</code> still is overloaded? The
+ answer is yes, it is overloaded, but with plain proxy
+ throughput requests, only! All SSI, CGI, ePerl, etc.
+ processing is completely done on the other machines.
+ This is the essential point.</div>
+ </li>
+
+ <li>
+ <strong>Hardware/TCP Round-Robin</strong>
+
+ <p>There is a hardware solution available, too. Cisco
+ has a beast called LocalDirector which does a load
+ balancing at the TCP/IP level. Actually this is some
+ sort of a circuit level gateway in front of a
+ webcluster. If you have enough money and really need
+ a solution with high performance, use this one.</p>
+ </li>
+ </ol>
+ </dd>
+ </dl>
+
+
+
+ <h3>New MIME-type, New Service</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>On the net there are a lot of nifty CGI programs. But
+ their usage is usually boring, so a lot of webmaster
+ don't use them. Even Apache's Action handler feature for
+ MIME-types is only appropriate when the CGI programs
+ don't need special URLs (actually <code>PATH_INFO</code>
+ and <code>QUERY_STRINGS</code>) as their input. First,
+ let us configure a new file type with extension
+ <code>.scgi</code> (for secure CGI) which will be processed
+ by the popular <code>cgiwrap</code> program. The problem
+ here is that for instance we use a Homogeneous URL Layout
+ (see above) a file inside the user homedirs has the URL
+ <code>/u/user/foo/bar.scgi</code>. But
+ <code>cgiwrap</code> needs the URL in the form
+ <code>/~user/foo/bar.scgi/</code>. The following rule
+ solves the problem:</p>
+
+<div class="example"><pre>
+RewriteRule ^/[uge]/<strong>([^/]+)</strong>/\.www/(.+)\.scgi(.*) ...
+... /internal/cgi/user/cgiwrap/~<strong>$1</strong>/$2.scgi$3 [NS,<strong>T=application/x-http-cgi</strong>]
+</pre></div>
+
+ <p>Or assume we have some more nifty programs:
+ <code>wwwlog</code> (which displays the
+ <code>access.log</code> for a URL subtree and
+ <code>wwwidx</code> (which runs Glimpse on a URL
+ subtree). We have to provide the URL area to these
+ programs so they know on which area they have to act on.
+ But usually this ugly, because they are all the times
+ still requested from that areas, i.e. typically we would
+ run the <code>swwidx</code> program from within
+ <code>/u/user/foo/</code> via hyperlink to</p>
+
+<div class="example"><pre>
+/internal/cgi/user/swwidx?i=/u/user/foo/
+</pre></div>
+
+ <p>which is ugly. Because we have to hard-code
+ <strong>both</strong> the location of the area
+ <strong>and</strong> the location of the CGI inside the
+ hyperlink. When we have to reorganize the area, we spend a
+ lot of time changing the various hyperlinks.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution here is to provide a special new URL format
+ which automatically leads to the proper CGI invocation.
+ We configure the following:</p>
+
+<div class="example"><pre>
+RewriteRule ^/([uge])/([^/]+)(/?.*)/\* /internal/cgi/user/wwwidx?i=/$1/$2$3/
+RewriteRule ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3
+</pre></div>
+
+ <p>Now the hyperlink to search at
+ <code>/u/user/foo/</code> reads only</p>
+
+<div class="example"><pre>
+HREF="*"
+</pre></div>
+
+ <p>which internally gets automatically transformed to</p>
+
+<div class="example"><pre>
+/internal/cgi/user/wwwidx?i=/u/user/foo/
+</pre></div>
+
+ <p>The same approach leads to an invocation for the
+ access log CGI program when the hyperlink
+ <code>:log</code> gets used.</p>
+ </dd>
+ </dl>
+
+
+
+ <h3>On-the-fly Content-Regeneration</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Here comes a really esoteric feature: Dynamically
+ generated but statically served pages, i.e. pages should be
+ delivered as pure static pages (read from the filesystem
+ and just passed through), but they have to be generated
+ dynamically by the webserver if missing. This way you can
+ have CGI-generated pages which are statically served unless
+ one (or a cronjob) removes the static contents. Then the
+ contents gets refreshed.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ This is done via the following ruleset:
+
+<div class="example"><pre>
+RewriteCond %{REQUEST_FILENAME} <strong>!-s</strong>
+RewriteRule ^page\.<strong>html</strong>$ page.<strong>cgi</strong> [T=application/x-httpd-cgi,L]
+</pre></div>
+
+ <p>Here a request to <code>page.html</code> leads to a
+ internal run of a corresponding <code>page.cgi</code> if
+ <code>page.html</code> is still missing or has filesize
+ null. The trick here is that <code>page.cgi</code> is a
+ usual CGI script which (additionally to its <code>STDOUT</code>)
+ writes its output to the file <code>page.html</code>.
+ Once it was run, the server sends out the data of
+ <code>page.html</code>. When the webmaster wants to force
+ a refresh the contents, he just removes
+ <code>page.html</code> (usually done by a cronjob).</p>
+ </dd>
+ </dl>
+
+
+
+ <h3>Document With Autorefresh</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Wouldn't it be nice while creating a complex webpage if
+ the webbrowser would automatically refresh the page every
+ time we write a new version from within our editor?
+ Impossible?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>No! We just combine the MIME multipart feature, the
+ webserver NPH feature and the URL manipulation power of
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. First, we establish a new
+ URL feature: Adding just <code>:refresh</code> to any
+ URL causes this to be refreshed every time it gets
+ updated on the filesystem.</p>
+
+<div class="example"><pre>
+RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1
+</pre></div>
+
+ <p>Now when we reference the URL</p>
+
+<div class="example"><pre>
+/u/foo/bar/page.html:refresh
+</pre></div>
+
+ <p>this leads to the internal invocation of the URL</p>
+
+<div class="example"><pre>
+/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
+</pre></div>
+
+ <p>The only missing part is the NPH-CGI script. Although
+ one would usually say "left as an exercise to the reader"
+ ;-) I will provide this, too.</p>
+
+<div class="example"><pre>
+#!/sw/bin/perl
+##
+## nph-refresh -- NPH/CGI script for auto refreshing pages
+## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
+##
+$| = 1;
+
+# split the QUERY_STRING variable
+@pairs = split(/&/, $ENV{'QUERY_STRING'});
+foreach $pair (@pairs) {
+ ($name, $value) = split(/=/, $pair);
+ $name =~ tr/A-Z/a-z/;
+ $name = 'QS_' . $name;
+ $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
+ eval "\$$name = \"$value\"";
+}
+$QS_s = 1 if ($QS_s eq '');
+$QS_n = 3600 if ($QS_n eq '');
+if ($QS_f eq '') {
+ print "HTTP/1.0 200 OK\n";
+ print "Content-type: text/html\n\n";
+ print "&lt;b&gt;ERROR&lt;/b&gt;: No file given\n";
+ exit(0);
+}
+if (! -f $QS_f) {
+ print "HTTP/1.0 200 OK\n";
+ print "Content-type: text/html\n\n";
+ print "&lt;b&gt;ERROR&lt;/b&gt;: File $QS_f not found\n";
+ exit(0);
+}
+
+sub print_http_headers_multipart_begin {
+ print "HTTP/1.0 200 OK\n";
+ $bound = "ThisRandomString12345";
+ print "Content-type: multipart/x-mixed-replace;boundary=$bound\n";
+ &print_http_headers_multipart_next;
+}
+
+sub print_http_headers_multipart_next {
+ print "\n--$bound\n";
+}
+
+sub print_http_headers_multipart_end {
+ print "\n--$bound--\n";
+}
+
+sub displayhtml {
+ local($buffer) = @_;
+ $len = length($buffer);
+ print "Content-type: text/html\n";
+ print "Content-length: $len\n\n";
+ print $buffer;
+}
+
+sub readfile {
+ local($file) = @_;
+ local(*FP, $size, $buffer, $bytes);
+ ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
+ $size = sprintf("%d", $size);
+ open(FP, "&lt;$file");
+ $bytes = sysread(FP, $buffer, $size);
+ close(FP);
+ return $buffer;
+}
+
+$buffer = &readfile($QS_f);
+&print_http_headers_multipart_begin;
+&displayhtml($buffer);
+
+sub mystat {
+ local($file) = $_[0];
+ local($time);
+
+ ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
+ return $mtime;
+}
+
+$mtimeL = &mystat($QS_f);
+$mtime = $mtime;
+for ($n = 0; $n &lt; $QS_n; $n++) {
+ while (1) {
+ $mtime = &mystat($QS_f);
+ if ($mtime ne $mtimeL) {
+ $mtimeL = $mtime;
+ sleep(2);
+ $buffer = &readfile($QS_f);
+ &print_http_headers_multipart_next;
+ &displayhtml($buffer);
+ sleep(5);
+ $mtimeL = &mystat($QS_f);
+ last;
+ }
+ sleep($QS_s);
+ }
+}
+
+&print_http_headers_multipart_end;
+
+exit(0);
+
+##EOF##
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Mass Virtual Hosting</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>The <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> feature of Apache is nice
+ and works great when you just have a few dozens
+ virtual hosts. But when you are an ISP and have hundreds of
+ virtual hosts to provide this feature is not the best
+ choice.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>To provide this feature we map the remote webpage or even
+ the complete remote webarea to our namespace by the use
+ of the <dfn>Proxy Throughput</dfn> feature (flag <code>[P]</code>):</p>
+
+<div class="example"><pre>
+##
+## vhost.map
+##
+www.vhost1.dom:80 /path/to/docroot/vhost1
+www.vhost2.dom:80 /path/to/docroot/vhost2
+ :
+www.vhostN.dom:80 /path/to/docroot/vhostN
+</pre></div>
+
+<div class="example"><pre>
+##
+## httpd.conf
+##
+ :
+# use the canonical hostname on redirects, etc.
+UseCanonicalName on
+
+ :
+# add the virtual host in front of the CLF-format
+CustomLog /path/to/access_log "%{VHOST}e %h %l %u %t \"%r\" %>s %b"
+ :
+
+# enable the rewriting engine in the main server
+RewriteEngine on
+
+# define two maps: one for fixing the URL and one which defines
+# the available virtual hosts with their corresponding
+# DocumentRoot.
+RewriteMap lowercase int:tolower
+RewriteMap vhost txt:/path/to/vhost.map
+
+# Now do the actual virtual host mapping
+# via a huge and complicated single rule:
+#
+# 1. make sure we don't map for common locations
+RewriteCond %{REQUEST_URI} !^/commonurl1/.*
+RewriteCond %{REQUEST_URI} !^/commonurl2/.*
+ :
+RewriteCond %{REQUEST_URI} !^/commonurlN/.*
+#
+# 2. make sure we have a Host header, because
+# currently our approach only supports
+# virtual hosting through this header
+RewriteCond %{HTTP_HOST} !^$
+#
+# 3. lowercase the hostname
+RewriteCond ${lowercase:%{HTTP_HOST}|NONE} ^(.+)$
+#
+# 4. lookup this hostname in vhost.map and
+# remember it only when it is a path
+# (and not "NONE" from above)
+RewriteCond ${vhost:%1} ^(/.*)$
+#
+# 5. finally we can map the URL to its docroot location
+# and remember the virtual host for logging puposes
+RewriteRule ^/(.*)$ %1/$1 [E=VHOST:${lowercase:%{HTTP_HOST}}]
+ :
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="access" id="access">Access Restriction</a></h2>
+
+
+
+ <h3>Host Deny</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a list of externally configured hosts
+ from using our server?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>For Apache >= 1.3b6:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteMap hosts-deny txt:/path/to/hosts.deny
+RewriteCond ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
+RewriteCond ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
+RewriteRule ^/.* - [F]
+</pre></div>
+
+ <p>For Apache <= 1.3b6:</p>
+
+<div class="example"><pre>
+RewriteEngine on
+RewriteMap hosts-deny txt:/path/to/hosts.deny
+RewriteRule ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1
+RewriteRule !^NOT-FOUND/.* - [F]
+RewriteRule ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1
+RewriteRule !^NOT-FOUND/.* - [F]
+RewriteRule ^NOT-FOUND/(.*)$ /$1
+</pre></div>
+
+<div class="example"><pre>
+##
+## hosts.deny
+##
+## ATTENTION! This is a map, not a list, even when we treat it as such.
+## mod_rewrite parses it for key/value pairs, so at least a
+## dummy value "-" must be present for each entry.
+##
+
+193.102.180.41 -
+bsdti1.sdm.de -
+192.76.162.40 -
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Proxy Deny</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a certain host or even a user of a
+ special host from using the Apache proxy?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We first have to make sure <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ is below(!) <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> in the Configuration
+ file when compiling the Apache webserver. This way it gets
+ called <em>before</em> <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. Then we
+ configure the following for a host-dependent deny...</p>
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_HOST} <strong>^badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></div>
+
+ <p>...and this one for a user@host-dependent deny:</p>
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>^badguy@badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Special Authentication Variant</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Sometimes a very special authentication is needed, for
+ instance a authentication which checks for a set of
+ explicitly configured users. Only these should receive
+ access and without explicit prompting (which would occur
+ when using the Basic Auth via <code class="module"><a href="../mod/mod_auth.html">mod_auth</a></code>).</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a list of rewrite conditions to exclude all except
+ our friends:</p>
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend1@client1.quux-corp\.com$</strong>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend2</strong>@client2.quux-corp\.com$
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend3</strong>@client3.quux-corp\.com$
+RewriteRule ^/~quux/only-for-friends/ - [F]
+</pre></div>
+ </dd>
+ </dl>
+
+
+
+ <h3>Referer-based Deflector</h3>
+
+
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we program a flexible URL Deflector which acts
+ on the "Referer" HTTP header and can be configured with as
+ many referring pages as we like?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use the following really tricky ruleset...</p>
+
+<div class="example"><pre>
+RewriteMap deflector txt:/path/to/deflector.map
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}} ^-$
+RewriteRule ^.* %{HTTP_REFERER} [R,L]
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND
+RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L]
+</pre></div>
+
+ <p>... in conjunction with a corresponding rewrite
+ map:</p>
+
+<div class="example"><pre>
+##
+## deflector.map
+##
+
+http://www.badguys.com/bad/index.html -
+http://www.badguys.com/bad/index2.html -
+http://www.badguys.com/bad/index3.html http://somewhere.com/
+</pre></div>
+
+ <p>This automatically redirects the request back to the
+ referring page (when "<code>-</code>" is used as the value
+ in the map) or to a specific URL (when an URL is specified
+ in the map as the second argument).</p>
+ </dd>
+ </dl>
+
+
+
+ </div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_guide_advanced.html" title="English"> en </a></p>
+</div><div id="footer">
+<p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html>
\ No newline at end of file
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
+<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
+<!-- $LastChangedRevision: 123578 $ -->
+
+<!--
+ Copyright 2002-2005 The Apache Software Foundation or its licensors, as
+ applicable.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<manualpage metafile="rewrite_guide_advanced.xml.meta">
+ <parentdocument href="./index.html" />
+
+ <title>URL Rewriting Guide - Advanced topics</title>
+
+ <summary>
+
+ <p>This document supplements the <module>mod_rewrite</module>
+ <a href="../mod/mod_rewrite.html">reference documentation</a>.
+ It describes how one can use Apache's <module>mod_rewrite</module>
+ to solve typical URL-based problems with which webmasters are
+ commonony confronted. We give detailed descriptions on how to
+ solve each problem by configuring URL rewriting rulesets.</p>
+
+ <note type="warning">ATTENTION: Depending on your server configuration
+ it may be necessary to slightly change the examples for your
+ situation, e.g. adding the <code>[PT]</code> flag when
+ additionally using <module>mod_alias</module> and
+ <module>mod_userdir</module>, etc. Or rewriting a ruleset
+ to fit in <code>.htaccess</code> context instead
+ of per-server context. Always try to understand what a
+ particular ruleset really does before you use it. This
+ avoids many problems.</note>
+
+ </summary>
+<seealso><a href="../mod/mod_rewrite.html">Module
+documentation</a></seealso>
+<seealso><a href="rewrite_intro.html">mod_rewrite
+introduction</a></seealso>
+<seealso><a href="rewrite_tech.html">Technical details</a></seealso>
+
+
+ <section id="cluster">
+
+ <title>Webcluster through Homogeneous URL Layout</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>We want to create a homogeneous and consistent URL
+ layout over all WWW servers on a Intranet webcluster, i.e.
+ all URLs (per definition server local and thus server
+ dependent!) become actually server <em>independent</em>!
+ What we want is to give the WWW namespace a consistent
+ server-independent layout: no URL should have to include
+ any physically correct target server. The cluster itself
+ should drive us automatically to the physical target
+ host.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First, the knowledge of the target servers come from
+ (distributed) external maps which contain information
+ where our users, groups and entities stay. The have the
+ form</p>
+
+<example><pre>
+user1 server_of_user1
+user2 server_of_user2
+: :
+</pre></example>
+
+ <p>We put them into files <code>map.xxx-to-host</code>.
+ Second we need to instruct all servers to redirect URLs
+ of the forms</p>
+
+<example><pre>
+/u/user/anypath
+/g/group/anypath
+/e/entity/anypath
+</pre></example>
+
+ <p>to</p>
+
+<example><pre>
+http://physical-host/u/user/anypath
+http://physical-host/g/group/anypath
+http://physical-host/e/entity/anypath
+</pre></example>
+
+ <p>when the URL is not locally valid to a server. The
+ following ruleset does this for us by the help of the map
+ files (assuming that server0 is a default server which
+ will be used if a user has no entry in the map):</p>
+
+<example><pre>
+RewriteEngine on
+
+RewriteMap user-to-host txt:/path/to/map.user-to-host
+RewriteMap group-to-host txt:/path/to/map.group-to-host
+RewriteMap entity-to-host txt:/path/to/map.entity-to-host
+
+RewriteRule ^/u/<strong>([^/]+)</strong>/?(.*) http://<strong>${user-to-host:$1|server0}</strong>/u/$1/$2
+RewriteRule ^/g/<strong>([^/]+)</strong>/?(.*) http://<strong>${group-to-host:$1|server0}</strong>/g/$1/$2
+RewriteRule ^/e/<strong>([^/]+)</strong>/?(.*) http://<strong>${entity-to-host:$1|server0}</strong>/e/$1/$2
+
+RewriteRule ^/([uge])/([^/]+)/?$ /$1/$2/.www/
+RewriteRule ^/([uge])/([^/]+)/([^.]+.+) /$1/$2/.www/$3\
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="structuredhomedirs">
+
+ <title>Structured Homedirs</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Some sites with thousands of users usually use a
+ structured homedir layout, i.e. each homedir is in a
+ subdirectory which begins for instance with the first
+ character of the username. So, <code>/~foo/anypath</code>
+ is <code>/home/<strong>f</strong>/foo/.www/anypath</code>
+ while <code>/~bar/anypath</code> is
+ <code>/home/<strong>b</strong>/bar/.www/anypath</code>.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use the following ruleset to expand the tilde URLs
+ into exactly the above layout.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteRule ^/~(<strong>([a-z])</strong>[a-z0-9]+)(.*) /home/<strong>$2</strong>/$1/.www$3
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="filereorg">
+
+ <title>Filesystem Reorganization</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>This really is a hardcore example: a killer application
+ which heavily uses per-directory
+ <code>RewriteRules</code> to get a smooth look and feel
+ on the Web while its data structure is never touched or
+ adjusted. Background: <strong><em>net.sw</em></strong> is
+ my archive of freely available Unix software packages,
+ which I started to collect in 1992. It is both my hobby
+ and job to to this, because while I'm studying computer
+ science I have also worked for many years as a system and
+ network administrator in my spare time. Every week I need
+ some sort of software so I created a deep hierarchy of
+ directories where I stored the packages:</p>
+
+<example><pre>
+drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/
+drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/
+drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/
+drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/
+drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/
+drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/
+drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/
+drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/
+drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/
+drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/
+drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/
+drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/
+drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/
+drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/
+drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/
+drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/
+</pre></example>
+
+ <p>In July 1996 I decided to make this archive public to
+ the world via a nice Web interface. "Nice" means that I
+ wanted to offer an interface where you can browse
+ directly through the archive hierarchy. And "nice" means
+ that I didn't wanted to change anything inside this
+ hierarchy - not even by putting some CGI scripts at the
+ top of it. Why? Because the above structure should be
+ later accessible via FTP as well, and I didn't want any
+ Web or CGI stuff to be there.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution has two parts: The first is a set of CGI
+ scripts which create all the pages at all directory
+ levels on-the-fly. I put them under
+ <code>/e/netsw/.www/</code> as follows:</p>
+
+<example><pre>
+-rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl
+drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/
+-rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE
+-rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO
+-rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html
+-rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl
+-rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi
+-rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi
+drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/
+-rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi
+-rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi
+-rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi
+-rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst
+</pre></example>
+
+ <p>The <code>DATA/</code> subdirectory holds the above
+ directory structure, i.e. the real
+ <strong><em>net.sw</em></strong> stuff and gets
+ automatically updated via <code>rdist</code> from time to
+ time. The second part of the problem remains: how to link
+ these two structures together into one smooth-looking URL
+ tree? We want to hide the <code>DATA/</code> directory
+ from the user while running the appropriate CGI scripts
+ for the various URLs. Here is the solution: first I put
+ the following into the per-directory configuration file
+ in the <directive module="core">DocumentRoot</directive>
+ of the server to rewrite the announced URL
+ <code>/net.sw/</code> to the internal path
+ <code>/e/netsw</code>:</p>
+
+<example><pre>
+RewriteRule ^net.sw$ net.sw/ [R]
+RewriteRule ^net.sw/(.*)$ e/netsw/$1
+</pre></example>
+
+ <p>The first rule is for requests which miss the trailing
+ slash! The second rule does the real thing. And then
+ comes the killer configuration which stays in the
+ per-directory config file
+ <code>/e/netsw/.www/.wwwacl</code>:</p>
+
+<example><pre>
+Options ExecCGI FollowSymLinks Includes MultiViews
+
+RewriteEngine on
+
+# we are reached via /net.sw/ prefix
+RewriteBase /net.sw/
+
+# first we rewrite the root dir to
+# the handling cgi script
+RewriteRule ^$ netsw-home.cgi [L]
+RewriteRule ^index\.html$ netsw-home.cgi [L]
+
+# strip out the subdirs when
+# the browser requests us from perdir pages
+RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L]
+
+# and now break the rewriting for local files
+RewriteRule ^netsw-home\.cgi.* - [L]
+RewriteRule ^netsw-changes\.cgi.* - [L]
+RewriteRule ^netsw-search\.cgi.* - [L]
+RewriteRule ^netsw-tree\.cgi$ - [L]
+RewriteRule ^netsw-about\.html$ - [L]
+RewriteRule ^netsw-img/.*$ - [L]
+
+# anything else is a subdir which gets handled
+# by another cgi script
+RewriteRule !^netsw-lsdir\.cgi.* - [C]
+RewriteRule (.*) netsw-lsdir.cgi/$1
+</pre></example>
+
+ <p>Some hints for interpretation:</p>
+
+ <ol>
+ <li>Notice the <code>L</code> (last) flag and no
+ substitution field ('<code>-</code>') in the forth part</li>
+
+ <li>Notice the <code>!</code> (not) character and
+ the <code>C</code> (chain) flag at the first rule
+ in the last part</li>
+
+ <li>Notice the catch-all pattern in the last rule</li>
+ </ol>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="redirect404">
+
+ <title>Redirect Failing URLs To Other Webserver</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>A typical FAQ about URL rewriting is how to redirect
+ failing requests on webserver A to webserver B. Usually
+ this is done via <directive module="core"
+ >ErrorDocument</directive> CGI-scripts in Perl, but
+ there is also a <module>mod_rewrite</module> solution.
+ But notice that this performs more poorly than using an
+ <directive module="core">ErrorDocument</directive>
+ CGI-script!</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The first solution has the best performance but less
+ flexibility, and is less error safe:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteCond /your/docroot/%{REQUEST_FILENAME} <strong>!-f</strong>
+RewriteRule ^(.+) http://<strong>webserverB</strong>.dom/$1
+</pre></example>
+
+ <p>The problem here is that this will only work for pages
+ inside the <directive module="core">DocumentRoot</directive>. While you can add more
+ Conditions (for instance to also handle homedirs, etc.)
+ there is better variant:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteCond %{REQUEST_URI} <strong>!-U</strong>
+RewriteRule ^(.+) http://<strong>webserverB</strong>.dom/$1
+</pre></example>
+
+ <p>This uses the URL look-ahead feature of <module>mod_rewrite</module>.
+ The result is that this will work for all types of URLs
+ and is a safe way. But it does a performance impact on
+ the webserver, because for every request there is one
+ more internal subrequest. So, if your webserver runs on a
+ powerful CPU, use this one. If it is a slow machine, use
+ the first approach or better a <directive module="core"
+ >ErrorDocument</directive> CGI-script.</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Archive Access Multiplexer</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Do you know the great CPAN (Comprehensive Perl Archive
+ Network) under <a href="http://www.perl.com/CPAN"
+ >http://www.perl.com/CPAN</a>?
+ This does a redirect to one of several FTP servers around
+ the world which carry a CPAN mirror and is approximately
+ near the location of the requesting client. Actually this
+ can be called an FTP access multiplexing service. While
+ CPAN runs via CGI scripts, how can a similar approach
+ implemented via <module>mod_rewrite</module>?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First we notice that from version 3.0.0
+ <module>mod_rewrite</module> can
+ also use the "<code>ftp:</code>" scheme on redirects.
+ And second, the location approximation can be done by a
+ <directive module="mod_rewrite">RewriteMap</directive>
+ over the top-level domain of the client.
+ With a tricky chained ruleset we can use this top-level
+ domain as a key to our multiplexing map.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteMap multiplex txt:/path/to/map.cxan
+RewriteRule ^/CxAN/(.*) %{REMOTE_HOST}::$1 [C]
+RewriteRule ^.+\.<strong>([a-zA-Z]+)</strong>::(.*)$ ${multiplex:<strong>$1</strong>|ftp.default.dom}$2 [R,L]
+</pre></example>
+
+<example><pre>
+##
+## map.cxan -- Multiplexing Map for CxAN
+##
+
+de ftp://ftp.cxan.de/CxAN/
+uk ftp://ftp.cxan.uk/CxAN/
+com ftp://ftp.cxan.com/CxAN/
+ :
+##EOF##
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section id="content">
+
+ <title>Content Handling</title>
+
+ <section>
+
+ <title>Browser Dependent Content</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>At least for important top-level pages it is sometimes
+ necessary to provide the optimum of browser dependent
+ content, i.e. one has to provide a maximum version for the
+ latest Netscape variants, a minimum version for the Lynx
+ browsers and a average feature version for all others.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We cannot use content negotiation because the browsers do
+ not provide their type in that form. Instead we have to
+ act on the HTTP header "User-Agent". The following condig
+ does the following: If the HTTP header "User-Agent"
+ begins with "Mozilla/3", the page <code>foo.html</code>
+ is rewritten to <code>foo.NS.html</code> and and the
+ rewriting stops. If the browser is "Lynx" or "Mozilla" of
+ version 1 or 2 the URL becomes <code>foo.20.html</code>.
+ All other browsers receive page <code>foo.32.html</code>.
+ This is done by the following ruleset:</p>
+
+<example><pre>
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Mozilla/3</strong>.*
+RewriteRule ^foo\.html$ foo.<strong>NS</strong>.html [<strong>L</strong>]
+
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Lynx/</strong>.* [OR]
+RewriteCond %{HTTP_USER_AGENT} ^<strong>Mozilla/[12]</strong>.*
+RewriteRule ^foo\.html$ foo.<strong>20</strong>.html [<strong>L</strong>]
+
+RewriteRule ^foo\.html$ foo.<strong>32</strong>.html [<strong>L</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Dynamic Mirror</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Assume there are nice webpages on remote hosts we want
+ to bring into our namespace. For FTP servers we would use
+ the <code>mirror</code> program which actually maintains an
+ explicit up-to-date copy of the remote data on the local
+ machine. For a webserver we could use the program
+ <code>webcopy</code> which acts similar via HTTP. But both
+ techniques have one major drawback: The local copy is
+ always just as up-to-date as often we run the program. It
+ would be much better if the mirror is not a static one we
+ have to establish explicitly. Instead we want a dynamic
+ mirror with data which gets updated automatically when
+ there is need (updated data on the remote host).</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>To provide this feature we map the remote webpage or even
+ the complete remote webarea to our namespace by the use
+ of the <dfn>Proxy Throughput</dfn> feature
+ (flag <code>[P]</code>):</p>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>hotsheet/</strong>(.*)$ <strong>http://www.tstimpreso.com/hotsheet/</strong>$1 [<strong>P</strong>]
+</pre></example>
+
+<example><pre>
+RewriteEngine on
+RewriteBase /~quux/
+RewriteRule ^<strong>usa-news\.html</strong>$ <strong>http://www.quux-corp.com/news/index.html</strong> [<strong>P</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Reverse Dynamic Mirror</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>...</dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+<example><pre>
+RewriteEngine on
+RewriteCond /mirror/of/remotesite/$1 -U
+RewriteRule ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Retrieve Missing Data from Intranet</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>This is a tricky way of virtually running a corporate
+ (external) Internet webserver
+ (<code>www.quux-corp.dom</code>), while actually keeping
+ and maintaining its data on a (internal) Intranet webserver
+ (<code>www2.quux-corp.dom</code>) which is protected by a
+ firewall. The trick is that on the external webserver we
+ retrieve the requested data on-the-fly from the internal
+ one.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>First, we have to make sure that our firewall still
+ protects the internal webserver and that only the
+ external webserver is allowed to retrieve data from it.
+ For a packet-filtering firewall we could for instance
+ configure a firewall ruleset like the following:</p>
+
+<example><pre>
+<strong>ALLOW</strong> Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port <strong>80</strong>
+<strong>DENY</strong> Host * Port * --> Host www2.quux-corp.dom Port <strong>80</strong>
+</pre></example>
+
+ <p>Just adjust it to your actual configuration syntax.
+ Now we can establish the <module>mod_rewrite</module>
+ rules which request the missing data in the background
+ through the proxy throughput feature:</p>
+
+<example><pre>
+RewriteRule ^/~([^/]+)/?(.*) /home/$1/.www/$2
+RewriteCond %{REQUEST_FILENAME} <strong>!-f</strong>
+RewriteCond %{REQUEST_FILENAME} <strong>!-d</strong>
+RewriteRule ^/home/([^/]+)/.www/?(.*) http://<strong>www2</strong>.quux-corp.dom/~$1/pub/$2 [<strong>P</strong>]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Load Balancing</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Suppose we want to load balance the traffic to
+ <code>www.foo.com</code> over <code>www[0-5].foo.com</code>
+ (a total of 6 servers). How can this be done?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>There are a lot of possible solutions for this problem.
+ We will discuss first a commonly known DNS-based variant
+ and then the special one with <module>mod_rewrite</module>:</p>
+
+ <ol>
+ <li>
+ <strong>DNS Round-Robin</strong>
+
+ <p>The simplest method for load-balancing is to use
+ the DNS round-robin feature of <code>BIND</code>.
+ Here you just configure <code>www[0-9].foo.com</code>
+ as usual in your DNS with A(address) records, e.g.</p>
+
+<example><pre>
+www0 IN A 1.2.3.1
+www1 IN A 1.2.3.2
+www2 IN A 1.2.3.3
+www3 IN A 1.2.3.4
+www4 IN A 1.2.3.5
+www5 IN A 1.2.3.6
+</pre></example>
+
+ <p>Then you additionally add the following entry:</p>
+
+<example><pre>
+www IN CNAME www0.foo.com.
+ IN CNAME www1.foo.com.
+ IN CNAME www2.foo.com.
+ IN CNAME www3.foo.com.
+ IN CNAME www4.foo.com.
+ IN CNAME www5.foo.com.
+ IN CNAME www6.foo.com.
+</pre></example>
+
+ <p>Notice that this seems wrong, but is actually an
+ intended feature of <code>BIND</code> and can be used
+ in this way. However, now when <code>www.foo.com</code> gets
+ resolved, <code>BIND</code> gives out <code>www0-www6</code>
+ - but in a slightly permutated/rotated order every time.
+ This way the clients are spread over the various
+ servers. But notice that this not a perfect load
+ balancing scheme, because DNS resolve information
+ gets cached by the other nameservers on the net, so
+ once a client has resolved <code>www.foo.com</code>
+ to a particular <code>wwwN.foo.com</code>, all
+ subsequent requests also go to this particular name
+ <code>wwwN.foo.com</code>. But the final result is
+ ok, because the total sum of the requests are really
+ spread over the various webservers.</p>
+ </li>
+
+ <li>
+ <strong>DNS Load-Balancing</strong>
+
+ <p>A sophisticated DNS-based method for
+ load-balancing is to use the program
+ <code>lbnamed</code> which can be found at <a
+ href="http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html">
+ http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html</a>.
+ It is a Perl 5 program in conjunction with auxilliary
+ tools which provides a real load-balancing for
+ DNS.</p>
+ </li>
+
+ <li>
+ <strong>Proxy Throughput Round-Robin</strong>
+
+ <p>In this variant we use <module>mod_rewrite</module>
+ and its proxy throughput feature. First we dedicate
+ <code>www0.foo.com</code> to be actually
+ <code>www.foo.com</code> by using a single</p>
+
+<example><pre>
+www IN CNAME www0.foo.com.
+</pre></example>
+
+ <p>entry in the DNS. Then we convert
+ <code>www0.foo.com</code> to a proxy-only server,
+ i.e. we configure this machine so all arriving URLs
+ are just pushed through the internal proxy to one of
+ the 5 other servers (<code>www1-www5</code>). To
+ accomplish this we first establish a ruleset which
+ contacts a load balancing script <code>lb.pl</code>
+ for all URLs.</p>
+
+<example><pre>
+RewriteEngine on
+RewriteMap lb prg:/path/to/lb.pl
+RewriteRule ^/(.+)$ ${lb:$1} [P,L]
+</pre></example>
+
+ <p>Then we write <code>lb.pl</code>:</p>
+
+<example><pre>
+#!/path/to/perl
+##
+## lb.pl -- load balancing script
+##
+
+$| = 1;
+
+$name = "www"; # the hostname base
+$first = 1; # the first server (not 0 here, because 0 is myself)
+$last = 5; # the last server in the round-robin
+$domain = "foo.dom"; # the domainname
+
+$cnt = 0;
+while (<STDIN>) {
+ $cnt = (($cnt+1) % ($last+1-$first));
+ $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain);
+ print "http://$server/$_";
+}
+
+##EOF##
+</pre></example>
+
+ <note>A last notice: Why is this useful? Seems like
+ <code>www0.foo.com</code> still is overloaded? The
+ answer is yes, it is overloaded, but with plain proxy
+ throughput requests, only! All SSI, CGI, ePerl, etc.
+ processing is completely done on the other machines.
+ This is the essential point.</note>
+ </li>
+
+ <li>
+ <strong>Hardware/TCP Round-Robin</strong>
+
+ <p>There is a hardware solution available, too. Cisco
+ has a beast called LocalDirector which does a load
+ balancing at the TCP/IP level. Actually this is some
+ sort of a circuit level gateway in front of a
+ webcluster. If you have enough money and really need
+ a solution with high performance, use this one.</p>
+ </li>
+ </ol>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>New MIME-type, New Service</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>On the net there are a lot of nifty CGI programs. But
+ their usage is usually boring, so a lot of webmaster
+ don't use them. Even Apache's Action handler feature for
+ MIME-types is only appropriate when the CGI programs
+ don't need special URLs (actually <code>PATH_INFO</code>
+ and <code>QUERY_STRINGS</code>) as their input. First,
+ let us configure a new file type with extension
+ <code>.scgi</code> (for secure CGI) which will be processed
+ by the popular <code>cgiwrap</code> program. The problem
+ here is that for instance we use a Homogeneous URL Layout
+ (see above) a file inside the user homedirs has the URL
+ <code>/u/user/foo/bar.scgi</code>. But
+ <code>cgiwrap</code> needs the URL in the form
+ <code>/~user/foo/bar.scgi/</code>. The following rule
+ solves the problem:</p>
+
+<example><pre>
+RewriteRule ^/[uge]/<strong>([^/]+)</strong>/\.www/(.+)\.scgi(.*) ...
+... /internal/cgi/user/cgiwrap/~<strong>$1</strong>/$2.scgi$3 [NS,<strong>T=application/x-http-cgi</strong>]
+</pre></example>
+
+ <p>Or assume we have some more nifty programs:
+ <code>wwwlog</code> (which displays the
+ <code>access.log</code> for a URL subtree and
+ <code>wwwidx</code> (which runs Glimpse on a URL
+ subtree). We have to provide the URL area to these
+ programs so they know on which area they have to act on.
+ But usually this ugly, because they are all the times
+ still requested from that areas, i.e. typically we would
+ run the <code>swwidx</code> program from within
+ <code>/u/user/foo/</code> via hyperlink to</p>
+
+<example><pre>
+/internal/cgi/user/swwidx?i=/u/user/foo/
+</pre></example>
+
+ <p>which is ugly. Because we have to hard-code
+ <strong>both</strong> the location of the area
+ <strong>and</strong> the location of the CGI inside the
+ hyperlink. When we have to reorganize the area, we spend a
+ lot of time changing the various hyperlinks.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>The solution here is to provide a special new URL format
+ which automatically leads to the proper CGI invocation.
+ We configure the following:</p>
+
+<example><pre>
+RewriteRule ^/([uge])/([^/]+)(/?.*)/\* /internal/cgi/user/wwwidx?i=/$1/$2$3/
+RewriteRule ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3
+</pre></example>
+
+ <p>Now the hyperlink to search at
+ <code>/u/user/foo/</code> reads only</p>
+
+<example><pre>
+HREF="*"
+</pre></example>
+
+ <p>which internally gets automatically transformed to</p>
+
+<example><pre>
+/internal/cgi/user/wwwidx?i=/u/user/foo/
+</pre></example>
+
+ <p>The same approach leads to an invocation for the
+ access log CGI program when the hyperlink
+ <code>:log</code> gets used.</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>On-the-fly Content-Regeneration</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Here comes a really esoteric feature: Dynamically
+ generated but statically served pages, i.e. pages should be
+ delivered as pure static pages (read from the filesystem
+ and just passed through), but they have to be generated
+ dynamically by the webserver if missing. This way you can
+ have CGI-generated pages which are statically served unless
+ one (or a cronjob) removes the static contents. Then the
+ contents gets refreshed.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ This is done via the following ruleset:
+
+<example><pre>
+RewriteCond %{REQUEST_FILENAME} <strong>!-s</strong>
+RewriteRule ^page\.<strong>html</strong>$ page.<strong>cgi</strong> [T=application/x-httpd-cgi,L]
+</pre></example>
+
+ <p>Here a request to <code>page.html</code> leads to a
+ internal run of a corresponding <code>page.cgi</code> if
+ <code>page.html</code> is still missing or has filesize
+ null. The trick here is that <code>page.cgi</code> is a
+ usual CGI script which (additionally to its <code>STDOUT</code>)
+ writes its output to the file <code>page.html</code>.
+ Once it was run, the server sends out the data of
+ <code>page.html</code>. When the webmaster wants to force
+ a refresh the contents, he just removes
+ <code>page.html</code> (usually done by a cronjob).</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Document With Autorefresh</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Wouldn't it be nice while creating a complex webpage if
+ the webbrowser would automatically refresh the page every
+ time we write a new version from within our editor?
+ Impossible?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>No! We just combine the MIME multipart feature, the
+ webserver NPH feature and the URL manipulation power of
+ <module>mod_rewrite</module>. First, we establish a new
+ URL feature: Adding just <code>:refresh</code> to any
+ URL causes this to be refreshed every time it gets
+ updated on the filesystem.</p>
+
+<example><pre>
+RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1
+</pre></example>
+
+ <p>Now when we reference the URL</p>
+
+<example><pre>
+/u/foo/bar/page.html:refresh
+</pre></example>
+
+ <p>this leads to the internal invocation of the URL</p>
+
+<example><pre>
+/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
+</pre></example>
+
+ <p>The only missing part is the NPH-CGI script. Although
+ one would usually say "left as an exercise to the reader"
+ ;-) I will provide this, too.</p>
+
+<example><pre>
+#!/sw/bin/perl
+##
+## nph-refresh -- NPH/CGI script for auto refreshing pages
+## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
+##
+$| = 1;
+
+# split the QUERY_STRING variable
+@pairs = split(/&/, $ENV{'QUERY_STRING'});
+foreach $pair (@pairs) {
+ ($name, $value) = split(/=/, $pair);
+ $name =~ tr/A-Z/a-z/;
+ $name = 'QS_' . $name;
+ $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
+ eval "\$$name = \"$value\"";
+}
+$QS_s = 1 if ($QS_s eq '');
+$QS_n = 3600 if ($QS_n eq '');
+if ($QS_f eq '') {
+ print "HTTP/1.0 200 OK\n";
+ print "Content-type: text/html\n\n";
+ print "&lt;b&gt;ERROR&lt;/b&gt;: No file given\n";
+ exit(0);
+}
+if (! -f $QS_f) {
+ print "HTTP/1.0 200 OK\n";
+ print "Content-type: text/html\n\n";
+ print "&lt;b&gt;ERROR&lt;/b&gt;: File $QS_f not found\n";
+ exit(0);
+}
+
+sub print_http_headers_multipart_begin {
+ print "HTTP/1.0 200 OK\n";
+ $bound = "ThisRandomString12345";
+ print "Content-type: multipart/x-mixed-replace;boundary=$bound\n";
+ &print_http_headers_multipart_next;
+}
+
+sub print_http_headers_multipart_next {
+ print "\n--$bound\n";
+}
+
+sub print_http_headers_multipart_end {
+ print "\n--$bound--\n";
+}
+
+sub displayhtml {
+ local($buffer) = @_;
+ $len = length($buffer);
+ print "Content-type: text/html\n";
+ print "Content-length: $len\n\n";
+ print $buffer;
+}
+
+sub readfile {
+ local($file) = @_;
+ local(*FP, $size, $buffer, $bytes);
+ ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
+ $size = sprintf("%d", $size);
+ open(FP, "&lt;$file");
+ $bytes = sysread(FP, $buffer, $size);
+ close(FP);
+ return $buffer;
+}
+
+$buffer = &readfile($QS_f);
+&print_http_headers_multipart_begin;
+&displayhtml($buffer);
+
+sub mystat {
+ local($file) = $_[0];
+ local($time);
+
+ ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
+ return $mtime;
+}
+
+$mtimeL = &mystat($QS_f);
+$mtime = $mtime;
+for ($n = 0; $n &lt; $QS_n; $n++) {
+ while (1) {
+ $mtime = &mystat($QS_f);
+ if ($mtime ne $mtimeL) {
+ $mtimeL = $mtime;
+ sleep(2);
+ $buffer = &readfile($QS_f);
+ &print_http_headers_multipart_next;
+ &displayhtml($buffer);
+ sleep(5);
+ $mtimeL = &mystat($QS_f);
+ last;
+ }
+ sleep($QS_s);
+ }
+}
+
+&print_http_headers_multipart_end;
+
+exit(0);
+
+##EOF##
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Mass Virtual Hosting</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>The <directive type="section" module="core"
+ >VirtualHost</directive> feature of Apache is nice
+ and works great when you just have a few dozens
+ virtual hosts. But when you are an ISP and have hundreds of
+ virtual hosts to provide this feature is not the best
+ choice.</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>To provide this feature we map the remote webpage or even
+ the complete remote webarea to our namespace by the use
+ of the <dfn>Proxy Throughput</dfn> feature (flag <code>[P]</code>):</p>
+
+<example><pre>
+##
+## vhost.map
+##
+www.vhost1.dom:80 /path/to/docroot/vhost1
+www.vhost2.dom:80 /path/to/docroot/vhost2
+ :
+www.vhostN.dom:80 /path/to/docroot/vhostN
+</pre></example>
+
+<example><pre>
+##
+## httpd.conf
+##
+ :
+# use the canonical hostname on redirects, etc.
+UseCanonicalName on
+
+ :
+# add the virtual host in front of the CLF-format
+CustomLog /path/to/access_log "%{VHOST}e %h %l %u %t \"%r\" %>s %b"
+ :
+
+# enable the rewriting engine in the main server
+RewriteEngine on
+
+# define two maps: one for fixing the URL and one which defines
+# the available virtual hosts with their corresponding
+# DocumentRoot.
+RewriteMap lowercase int:tolower
+RewriteMap vhost txt:/path/to/vhost.map
+
+# Now do the actual virtual host mapping
+# via a huge and complicated single rule:
+#
+# 1. make sure we don't map for common locations
+RewriteCond %{REQUEST_URI} !^/commonurl1/.*
+RewriteCond %{REQUEST_URI} !^/commonurl2/.*
+ :
+RewriteCond %{REQUEST_URI} !^/commonurlN/.*
+#
+# 2. make sure we have a Host header, because
+# currently our approach only supports
+# virtual hosting through this header
+RewriteCond %{HTTP_HOST} !^$
+#
+# 3. lowercase the hostname
+RewriteCond ${lowercase:%{HTTP_HOST}|NONE} ^(.+)$
+#
+# 4. lookup this hostname in vhost.map and
+# remember it only when it is a path
+# (and not "NONE" from above)
+RewriteCond ${vhost:%1} ^(/.*)$
+#
+# 5. finally we can map the URL to its docroot location
+# and remember the virtual host for logging puposes
+RewriteRule ^/(.*)$ %1/$1 [E=VHOST:${lowercase:%{HTTP_HOST}}]
+ :
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ </section>
+
+ <section id="access">
+
+ <title>Access Restriction</title>
+
+ <section>
+
+ <title>Host Deny</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a list of externally configured hosts
+ from using our server?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>For Apache >= 1.3b6:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteMap hosts-deny txt:/path/to/hosts.deny
+RewriteCond ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
+RewriteCond ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
+RewriteRule ^/.* - [F]
+</pre></example>
+
+ <p>For Apache <= 1.3b6:</p>
+
+<example><pre>
+RewriteEngine on
+RewriteMap hosts-deny txt:/path/to/hosts.deny
+RewriteRule ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1
+RewriteRule !^NOT-FOUND/.* - [F]
+RewriteRule ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1
+RewriteRule !^NOT-FOUND/.* - [F]
+RewriteRule ^NOT-FOUND/(.*)$ /$1
+</pre></example>
+
+<example><pre>
+##
+## hosts.deny
+##
+## ATTENTION! This is a map, not a list, even when we treat it as such.
+## mod_rewrite parses it for key/value pairs, so at least a
+## dummy value "-" must be present for each entry.
+##
+
+193.102.180.41 -
+bsdti1.sdm.de -
+192.76.162.40 -
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Proxy Deny</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we forbid a certain host or even a user of a
+ special host from using the Apache proxy?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We first have to make sure <module>mod_rewrite</module>
+ is below(!) <module>mod_proxy</module> in the Configuration
+ file when compiling the Apache webserver. This way it gets
+ called <em>before</em> <module>mod_proxy</module>. Then we
+ configure the following for a host-dependent deny...</p>
+
+<example><pre>
+RewriteCond %{REMOTE_HOST} <strong>^badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></example>
+
+ <p>...and this one for a user@host-dependent deny:</p>
+
+<example><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>^badguy@badhost\.mydomain\.com$</strong>
+RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Special Authentication Variant</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>Sometimes a very special authentication is needed, for
+ instance a authentication which checks for a set of
+ explicitly configured users. Only these should receive
+ access and without explicit prompting (which would occur
+ when using the Basic Auth via <module>mod_auth</module>).</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>We use a list of rewrite conditions to exclude all except
+ our friends:</p>
+
+<example><pre>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend1@client1.quux-corp\.com$</strong>
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend2</strong>@client2.quux-corp\.com$
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <strong>!^friend3</strong>@client3.quux-corp\.com$
+RewriteRule ^/~quux/only-for-friends/ - [F]
+</pre></example>
+ </dd>
+ </dl>
+
+ </section>
+
+ <section>
+
+ <title>Referer-based Deflector</title>
+
+ <dl>
+ <dt>Description:</dt>
+
+ <dd>
+ <p>How can we program a flexible URL Deflector which acts
+ on the "Referer" HTTP header and can be configured with as
+ many referring pages as we like?</p>
+ </dd>
+
+ <dt>Solution:</dt>
+
+ <dd>
+ <p>Use the following really tricky ruleset...</p>
+
+<example><pre>
+RewriteMap deflector txt:/path/to/deflector.map
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}} ^-$
+RewriteRule ^.* %{HTTP_REFERER} [R,L]
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND
+RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L]
+</pre></example>
+
+ <p>... in conjunction with a corresponding rewrite
+ map:</p>
+
+<example><pre>
+##
+## deflector.map
+##
+
+http://www.badguys.com/bad/index.html -
+http://www.badguys.com/bad/index2.html -
+http://www.badguys.com/bad/index3.html http://somewhere.com/
+</pre></example>
+
+ <p>This automatically redirects the request back to the
+ referring page (when "<code>-</code>" is used as the value
+ in the map) or to a specific URL (when an URL is specified
+ in the map as the second argument).</p>
+ </dd>
+ </dl>
+
+ </section>
+
+ </section>
+
+</manualpage>
+
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<metafile>
+ <basename>rewrite_guide_advanced</basename>
+ <path>/rewrite/</path>
+ <relpath>..</relpath>
+
+ <variants>
+ <variant>en</variant>
+ </variants>
+</metafile>
--- /dev/null
+URI: rewrite_intro.html.en
+Content-Language: en
+Content-type: text/html; charset=ISO-8859-1
--- /dev/null
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>Apache mod_rewrite Introduction - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./index.html"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Apache mod_rewrite Introduction</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_intro.html" title="English"> en </a></p>
+</div>
+
+<p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+<a href="../mod/mod_rewrite.html">reference documentation</a>. It
+describes the basic concepts necessary for use of
+<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. Other documents go into greater detail,
+but this doc should help the beginner get their feet wet.
+</p>
+</div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#introduction">Introduction</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#regex">Regular Expressions</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewriterule">RewriteRule basics</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#flags">Rewrite Flags</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritecond">Rewrite conditions</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritemap">Rewrite maps</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#htaccess">.htaccess files</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#EnvVar">Environment Variables</a></li>
+</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module
+documentation</a></li><li><a href="rewrite_tech.html">Technical details</a></li><li><a href="rewrite_guide.html">Practical solutions to common
+problems</a></li></ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="introduction" id="introduction">Introduction</a></h2>
+<p>The Apache module <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is a very powerful and
+sophisticated module which provides a way to do URL manipulations. With
+it, you can do nearly all types of URL rewriting that you may need. It
+is, however, somewhat complex, and may be intimidating to the beginner.
+There is also a tendency to treat rewrite rules as magic incantation,
+using them without actually understanding what they do.</p>
+
+<p>This document attempts to give sufficient background so that what
+follows is understood, rather than just copied blindly.
+</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="regex" id="regex">Regular Expressions</a></h2>
+<p>Basic regex building blocks</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="rewriterule" id="rewriterule">RewriteRule basics</a></h2>
+<p>
+Basic anatomy of a RewriteRule, with exhaustively annotated simple
+examples.
+</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="flags" id="flags">Rewrite Flags</a></h2>
+<p>Discussion of the flags to RewriteRule, and when and why one might
+use them.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="rewritecond" id="rewritecond">Rewrite conditions</a></h2>
+<p>Discussion of RewriteCond, looping, and other related concepts.
+</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="rewritemap" id="rewritemap">Rewrite maps</a></h2>
+<p>Discussion of RewriteMap, including simple, but heavily annotated,
+examples.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="htaccess" id="htaccess">.htaccess files</a></h2>
+<p>Discussion of the differences between rewrite rules in httpd.conf and
+in .htaccess files.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="EnvVar" id="EnvVar">Environment Variables</a></h2>
+
+<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>, <em>i.e.</em>, <em>before</em> any
+rewriting. This is important because the rewriting process is
+primarily used to rewrite logical URLs to physical
+pathnames.</p>
+
+<div class="example"><h3>Example</h3><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></div>
+
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_intro.html" title="English"> en </a></p>
+</div><div id="footer">
+<p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html>
\ No newline at end of file
--- /dev/null
+<?xml version='1.0' encoding='UTF-8' ?>
+<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
+<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
+<!-- $LastChangedRevision$ -->
+
+<!--
+ Copyright 2002-2005 The Apache Software Foundation or its licensors, as
+ applicable.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<manualpage metafile="rewrite_intro.xml.meta">
+<parentdocument href="./index.html"/>
+
+ <title>Apache mod_rewrite Introduction</title>
+
+<summary>
+<p>This document supplements the <module>mod_rewrite</module>
+<a href="../mod/mod_rewrite.html">reference documentation</a>. It
+describes the basic concepts necessary for use of
+<module>mod_rewrite</module>. Other documents go into greater detail,
+but this doc should help the beginner get their feet wet.
+</p>
+</summary>
+
+<seealso><a href="../mod/mod_rewrite.html">Module
+documentation</a></seealso>
+<seealso><a href="rewrite_tech.html">Technical details</a></seealso>
+<seealso><a href="rewrite_guide.html">Practical solutions to common
+problems</a></seealso>
+
+<section id="introduction"><title>Introduction</title>
+<p>The Apache module <module>mod_rewrite</module> is a very powerful and
+sophisticated module which provides a way to do URL manipulations. With
+it, you can do nearly all types of URL rewriting that you may need. It
+is, however, somewhat complex, and may be intimidating to the beginner.
+There is also a tendency to treat rewrite rules as magic incantation,
+using them without actually understanding what they do.</p>
+
+<p>This document attempts to give sufficient background so that what
+follows is understood, rather than just copied blindly.
+</p>
+</section>
+
+<section id="regex"><title>Regular Expressions</title>
+<p>Basic regex building blocks</p>
+</section>
+
+<section id="rewriterule"><title>RewriteRule basics</title>
+<p>
+Basic anatomy of a RewriteRule, with exhaustively annotated simple
+examples.
+</p>
+</section>
+
+<section id="flags"><title>Rewrite Flags</title>
+<p>Discussion of the flags to RewriteRule, and when and why one might
+use them.</p>
+</section>
+
+<section id="rewritecond"><title>Rewrite conditions</title>
+<p>Discussion of RewriteCond, looping, and other related concepts.
+</p>
+</section>
+
+<section id="rewritemap"><title>Rewrite maps</title>
+<p>Discussion of RewriteMap, including simple, but heavily annotated,
+examples.</p>
+</section>
+
+<section id="htaccess"><title>.htaccess files</title>
+<p>Discussion of the differences between rewrite rules in httpd.conf and
+in .htaccess files.</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>, <em>i.e.</em>, <em>before</em> any
+rewriting. This is important 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>
+
+</manualpage>
+
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<metafile>
+ <basename>rewrite_intro</basename>
+ <path>/rewrite/</path>
+ <relpath>..</relpath>
+
+ <variants>
+ <variant>en</variant>
+ </variants>
+</metafile>
--- /dev/null
+URI: rewrite_tech.html.en
+Content-Language: en
+Content-type: text/html; charset=ISO-8859-1
--- /dev/null
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>Apache mod_rewrite Technical Details - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./index.html"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Apache mod_rewrite Technical Details</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_tech.html" title="English"> en </a></p>
+</div>
+
+<p>This document discusses some of the technical details of mod_rewrite
+and URL matching.</p>
+</div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#Internal">Internal Processing</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#InternalAPI">API Phases</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#InternalRuleset">Ruleset Processing</a></li>
+</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module
+documentation</a></li><li><a href="rewrite_intro.html">mod_rewrite
+introduction</a></li><li><a href="rewrite_guide.html">Practical solutions to common
+problems</a></li></ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="Internal" id="Internal">Internal Processing</a></h2>
+
+ <p>The internal processing of this module is very complex but
+ needs to be explained once even to the average user to avoid
+ common mistakes and to let you exploit its full
+ functionality.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="InternalAPI" id="InternalAPI">API Phases</a></h2>
+
+ <p>First you have to understand that when Apache processes a
+ HTTP request it does this in phases. A hook for each of these
+ phases is provided by the Apache API. Mod_rewrite uses two of
+ these hooks: the URL-to-filename translation hook which is
+ used after the HTTP request has been read but before any
+ authorization starts and the Fixup hook which is triggered
+ after the authorization phases and after the per-directory
+ config files (<code>.htaccess</code>) have been read, but
+ before the content handler is activated.</p>
+
+ <p>So, after a request comes in and Apache has determined the
+ corresponding server (or virtual server) the rewriting engine
+ starts processing of all mod_rewrite directives from the
+ per-server configuration in the URL-to-filename phase. A few
+ steps later when the final data directories are found, the
+ per-directory configuration directives of mod_rewrite are
+ triggered in the Fixup phase. In both situations mod_rewrite
+ rewrites URLs either to new URLs or to filenames, although
+ there is no obvious distinction between them. This is a usage
+ of the API which was not intended to be this way when the API
+ was designed, but as of Apache 1.x this is the only way
+ mod_rewrite can operate. To make this point more clear
+ remember the following two points:</p>
+
+ <ol>
+ <li>Although mod_rewrite rewrites URLs to URLs, URLs to
+ filenames and even filenames to filenames, the API
+ currently provides only a URL-to-filename hook. In Apache
+ 2.0 the two missing hooks will be added to make the
+ processing more clear. But this point has no drawbacks for
+ the user, it is just a fact which should be remembered:
+ Apache does more in the URL-to-filename hook than the API
+ intends for it.</li>
+
+ <li>
+ Unbelievably mod_rewrite provides URL manipulations in
+ per-directory context, <em>i.e.</em>, within
+ <code>.htaccess</code> files, although these are reached
+ a very long time after the URLs have been translated to
+ filenames. It has to be this way because
+ <code>.htaccess</code> files live in the filesystem, so
+ processing has already reached this stage. In other
+ words: According to the API phases at this time it is too
+ late for any URL manipulations. To overcome this chicken
+ and egg problem mod_rewrite uses a trick: When you
+ manipulate a URL/filename in per-directory context
+ mod_rewrite first rewrites the filename back to its
+ corresponding URL (which is usually impossible, but see
+ the <code>RewriteBase</code> directive below for the
+ trick to achieve this) and then initiates a new internal
+ sub-request with the new URL. This restarts processing of
+ the API phases.
+
+ <p>Again mod_rewrite tries hard to make this complicated
+ step totally transparent to the user, but you should
+ remember here: While URL manipulations in per-server
+ context are really fast and efficient, per-directory
+ rewrites are slow and inefficient due to this chicken and
+ egg problem. But on the other hand this is the only way
+ mod_rewrite can provide (locally restricted) URL
+ manipulations to the average user.</p>
+ </li>
+ </ol>
+
+ <p>Don't forget these two points!</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="InternalRuleset" id="InternalRuleset">Ruleset Processing</a></h2>
+
+ <p>Now when mod_rewrite is triggered in these two API phases, it
+ reads the configured rulesets from its configuration
+ structure (which itself was either created on startup for
+ per-server context or during the directory walk of the Apache
+ kernel for per-directory context). Then the URL rewriting
+ engine is started with the contained ruleset (one or more
+ rules together with their conditions). The operation of the
+ URL rewriting engine itself is exactly the same for both
+ configuration contexts. Only the final result processing is
+ different. </p>
+
+ <p>The order of rules in the ruleset is important because the
+ rewriting engine processes them in a special (and not very
+ obvious) order. The rule is this: The rewriting engine loops
+ through the ruleset rule by rule (<code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> directives) and
+ when a particular rule matches it optionally loops through
+ existing corresponding conditions (<code>RewriteCond</code>
+ directives). For historical reasons the conditions are given
+ first, and so the control flow is a little bit long-winded. See
+ Figure 1 for more details.</p>
+<p class="figure">
+ <img src="../images/mod_rewrite_fig1.gif" width="428" height="385" alt="[Needs graphics capability to display]" /><br />
+ <dfn>Figure 1:</dfn>The control flow through the rewriting ruleset
+</p>
+ <p>As you can see, first the URL is matched against the
+ <em>Pattern</em> of each rule. When it fails mod_rewrite
+ immediately stops processing this rule and continues with the
+ next rule. If the <em>Pattern</em> matches, mod_rewrite looks
+ for corresponding rule conditions. If none are present, it
+ just substitutes the URL with a new value which is
+ constructed from the string <em>Substitution</em> and goes on
+ with its rule-looping. But if conditions exist, it starts an
+ inner loop for processing them in the order that they are
+ listed. For conditions the logic is different: we don't match
+ a pattern against the current URL. Instead we first create a
+ string <em>TestString</em> by expanding variables,
+ back-references, map lookups, <em>etc.</em> and then we try
+ to match <em>CondPattern</em> against it. If the pattern
+ doesn't match, the complete set of conditions and the
+ corresponding rule fails. If the pattern matches, then the
+ next condition is processed until no more conditions are
+ available. If all conditions match, processing is continued
+ with the substitution of the URL with
+ <em>Substitution</em>.</p>
+
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/rewrite/rewrite_tech.html" title="English"> en </a></p>
+</div><div id="footer">
+<p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
+</body></html>
\ No newline at end of file
--- /dev/null
+<?xml version='1.0' encoding='UTF-8' ?>
+<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd">
+<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
+<!-- $LastChangedRevision$ -->
+
+<!--
+ Copyright 2002-2005 The Apache Software Foundation or its licensors, as
+ applicable.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+<manualpage metafile="rewrite_tech.xml.meta">
+<parentdocument href="./index.html"/>
+
+ <title>Apache mod_rewrite Technical Details</title>
+
+<summary>
+<p>This document discusses some of the technical details of mod_rewrite
+and URL matching.</p>
+</summary>
+<seealso><a href="../mod/mod_rewrite.html">Module
+documentation</a></seealso>
+<seealso><a href="rewrite_intro.html">mod_rewrite
+introduction</a></seealso>
+<seealso><a href="rewrite_guide.html">Practical solutions to common
+problems</a></seealso>
+
+<section id="Internal"><title>Internal Processing</title>
+
+ <p>The internal processing of this module is very complex but
+ needs to be explained once even to the average user to avoid
+ common mistakes and to let you exploit its full
+ functionality.</p>
+</section>
+
+<section id="InternalAPI"><title>API Phases</title>
+
+ <p>First you have to understand that when Apache processes a
+ HTTP request it does this in phases. A hook for each of these
+ phases is provided by the Apache API. Mod_rewrite uses two of
+ these hooks: the URL-to-filename translation hook which is
+ used after the HTTP request has been read but before any
+ authorization starts and the Fixup hook which is triggered
+ after the authorization phases and after the per-directory
+ config files (<code>.htaccess</code>) have been read, but
+ before the content handler is activated.</p>
+
+ <p>So, after a request comes in and Apache has determined the
+ corresponding server (or virtual server) the rewriting engine
+ starts processing of all mod_rewrite directives from the
+ per-server configuration in the URL-to-filename phase. A few
+ steps later when the final data directories are found, the
+ per-directory configuration directives of mod_rewrite are
+ triggered in the Fixup phase. In both situations mod_rewrite
+ rewrites URLs either to new URLs or to filenames, although
+ there is no obvious distinction between them. This is a usage
+ of the API which was not intended to be this way when the API
+ was designed, but as of Apache 1.x this is the only way
+ mod_rewrite can operate. To make this point more clear
+ remember the following two points:</p>
+
+ <ol>
+ <li>Although mod_rewrite rewrites URLs to URLs, URLs to
+ filenames and even filenames to filenames, the API
+ currently provides only a URL-to-filename hook. In Apache
+ 2.0 the two missing hooks will be added to make the
+ processing more clear. But this point has no drawbacks for
+ the user, it is just a fact which should be remembered:
+ Apache does more in the URL-to-filename hook than the API
+ intends for it.</li>
+
+ <li>
+ Unbelievably mod_rewrite provides URL manipulations in
+ per-directory context, <em>i.e.</em>, within
+ <code>.htaccess</code> files, although these are reached
+ a very long time after the URLs have been translated to
+ filenames. It has to be this way because
+ <code>.htaccess</code> files live in the filesystem, so
+ processing has already reached this stage. In other
+ words: According to the API phases at this time it is too
+ late for any URL manipulations. To overcome this chicken
+ and egg problem mod_rewrite uses a trick: When you
+ manipulate a URL/filename in per-directory context
+ mod_rewrite first rewrites the filename back to its
+ corresponding URL (which is usually impossible, but see
+ the <code>RewriteBase</code> directive below for the
+ trick to achieve this) and then initiates a new internal
+ sub-request with the new URL. This restarts processing of
+ the API phases.
+
+ <p>Again mod_rewrite tries hard to make this complicated
+ step totally transparent to the user, but you should
+ remember here: While URL manipulations in per-server
+ context are really fast and efficient, per-directory
+ rewrites are slow and inefficient due to this chicken and
+ egg problem. But on the other hand this is the only way
+ mod_rewrite can provide (locally restricted) URL
+ manipulations to the average user.</p>
+ </li>
+ </ol>
+
+ <p>Don't forget these two points!</p>
+</section>
+
+<section id="InternalRuleset"><title>Ruleset Processing</title>
+
+ <p>Now when mod_rewrite is triggered in these two API phases, it
+ reads the configured rulesets from its configuration
+ structure (which itself was either created on startup for
+ per-server context or during the directory walk of the Apache
+ kernel for per-directory context). Then the URL rewriting
+ engine is started with the contained ruleset (one or more
+ rules together with their conditions). The operation of the
+ URL rewriting engine itself is exactly the same for both
+ configuration contexts. Only the final result processing is
+ different. </p>
+
+ <p>The order of rules in the ruleset is important because the
+ rewriting engine processes them in a special (and not very
+ obvious) order. The rule is this: The rewriting engine loops
+ through the ruleset rule by rule (<directive
+ module="mod_rewrite">RewriteRule</directive> directives) and
+ when a particular rule matches it optionally loops through
+ existing corresponding conditions (<code>RewriteCond</code>
+ directives). For historical reasons the conditions are given
+ first, and so the control flow is a little bit long-winded. See
+ Figure 1 for more details.</p>
+<p class="figure">
+ <img src="../images/mod_rewrite_fig1.gif" width="428"
+ height="385" alt="[Needs graphics capability to display]" /><br />
+ <dfn>Figure 1:</dfn>The control flow through the rewriting ruleset
+</p>
+ <p>As you can see, first the URL is matched against the
+ <em>Pattern</em> of each rule. When it fails mod_rewrite
+ immediately stops processing this rule and continues with the
+ next rule. If the <em>Pattern</em> matches, mod_rewrite looks
+ for corresponding rule conditions. If none are present, it
+ just substitutes the URL with a new value which is
+ constructed from the string <em>Substitution</em> and goes on
+ with its rule-looping. But if conditions exist, it starts an
+ inner loop for processing them in the order that they are
+ listed. For conditions the logic is different: we don't match
+ a pattern against the current URL. Instead we first create a
+ string <em>TestString</em> by expanding variables,
+ back-references, map lookups, <em>etc.</em> and then we try
+ to match <em>CondPattern</em> against it. If the pattern
+ doesn't match, the complete set of conditions and the
+ corresponding rule fails. If the pattern matches, then the
+ next condition is processed until no more conditions are
+ available. If all conditions match, processing is continued
+ with the substitution of the URL with
+ <em>Substitution</em>.</p>
+
+</section>
+
+
+</manualpage>
+
--- /dev/null
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<metafile>
+ <basename>rewrite_tech</basename>
+ <path>/rewrite/</path>
+ <relpath>..</relpath>
+
+ <variants>
+ <variant>en</variant>
+ </variants>
+</metafile>
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