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<title>URL Rewriting Guide - Apache HTTP Server</title>
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<p class="menu"><a href="../mod/index.html">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/index.html">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.2</p>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../index.html">Version 2.2</a> > <a href="./index.html">Rewrite</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
commonly 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" /> <a href="#time-dependent">Time-Dependent Rewriting</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#backward-compatibility">Backward Compatibility for YYYY to XXXX migration</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#old-to-new">From Old to New (intern)</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#old-to-new-extern">From Old to New (extern)</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#static-to-dynamic">From Static to Dynamic</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#blocking-of-robots">Blocking of Robots</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#blocked-inline-images">Blocked Inline-Images</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#proxy-deny">Proxy Deny</a></li>
<li><img alt="" src="../../images/down.gif" /> <a href="#external-rewriting">External Rewriting Engine</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_advanced.html">Advanced Rewrite Guide - advanced
useful examples</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/$2 [<strong>R</strong>]
RewriteRule ^/u/(<strong>[^/]+</strong>)$ /$1/$2<strong>/</strong> [<strong>R</strong>]
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="canonicalhost" id="canonicalhost">Canonical Hostnames</a></h2>
<dl>
<dt>Description:</dt>
<dd>The goal of this rule is to force the use of a particular
hostname, in preference to other hostnames which may be used to
reach the same site. For example, if you wish to force the use
of <strong>www.example.com</strong> instead of
<strong>example.com</strong>, you might use a variant of the
following recipe.</dd>
<dt>Solution:</dt>
<dd>
<p>For sites running on a port other than 80:</p>
<div class="example"><pre>
RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST} !^$
RewriteCond %{SERVER_PORT} !^80$
RewriteRule ^/?(.*) http://www.example.com:%{SERVER_PORT}/$1 [L,R,NE]
</pre></div>
<p>And for a site running on port 80</p>
<div class="example"><pre>
RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST} !^$
RewriteRule ^/?(.*) http://www.example.com/$1 [L,R,NE]
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="moveddocroot" id="moveddocroot">Moved <code>DocumentRoot</code></a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>Usually the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
of the webserver directly relates to the URL "<code>/</code>".
But often this data is not really of top-level priority. For example,
you may wish for visitors, on first entering a site, to go to a
particular subdirectory <code>/about/</code>. This may be accomplished
using the following ruleset:</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We redirect the URL <code>/</code> to
<code>/about/</code>:
</p>
<div class="example"><pre>
RewriteEngine on
RewriteRule <strong>^/$</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 dir1/...
# ...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 dir2/...
# ...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/$1 [R,L]
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="redirectanchors" id="redirectanchors">Redirecting Anchors</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>By default, redirecting to an HTML anchor doesn't work,
because mod_rewrite escapes the <code>#</code> character,
turning it into <code>%23</code>. This, in turn, breaks the
redirection.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>Use the <code>[NE]</code> flag on the
<code>RewriteRule</code>. NE stands for No Escape.
</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="time-dependent" id="time-dependent">Time-Dependent Rewriting</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>When tricks like time-dependent content should happen a
lot of webmasters still use CGI scripts which do for
instance redirects to specialized pages. How can it be done
via <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>?</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>There are a lot of variables named <code>TIME_xxx</code>
for rewrite conditions. In conjunction with the special
lexicographic comparison patterns <code><STRING</code>,
<code>>STRING</code> and <code>=STRING</code> we can
do time-dependent redirects:</p>
<div class="example"><pre>
RewriteEngine on
RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700
RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900
RewriteRule ^foo\.html$ 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><a name="backward-compatibility" id="backward-compatibility">Backward Compatibility for YYYY to XXXX migration</a></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 ^(.*)$ $1.html
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="old-to-new" id="old-to-new">From Old to New (intern)</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>Assume we have recently renamed the page
<code>foo.html</code> to <code>bar.html</code> and now want
to provide the old URL for backward compatibility. Actually
we want that users of the old URL even not recognize that
the pages was renamed.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We rewrite the old URL to the new one internally via the
following rule:</p>
<div class="example"><pre>
RewriteEngine on
RewriteBase /~quux/
RewriteRule ^<strong>foo</strong>\.html$ <strong>bar</strong>.html
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="old-to-new-extern" id="old-to-new-extern">From Old to New (extern)</a></h2>
<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>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="static-to-dynamic" id="static-to-dynamic">From Static to Dynamic</a></h2>
<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
handler to be <strong>cgi-script</strong> so that it is
executed as a CGI program.
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> [H=<strong>cgi-script</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="blocking-of-robots" id="blocking-of-robots">Blocking of Robots</a></h2>
<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>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="blocked-inline-images" id="blocked-inline-images">Blocked Inline-Images</a></h2>
<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$</strong> - [F]
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="proxy-deny" id="proxy-deny">Proxy Deny</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>How can we forbid a certain host or even a user of a
special host from using the Apache proxy?</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We first have to make sure <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
is below(!) <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> in the Configuration
file when compiling the Apache webserver. This way it gets
called <em>before</em> <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. Then we
configure the following for a host-dependent deny...</p>
<div class="example"><pre>
RewriteCond %{REMOTE_HOST} <strong>^badhost\.mydomain\.com$</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$</strong>
RewriteRule !^http://[^/.]\.mydomain.com.* - [F]
</pre></div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../../images/up.gif" /></a></div>
<div class="section">
<h2><a name="external-rewriting" id="external-rewriting">External Rewriting Engine</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>A FAQ: How can we solve the FOO/BAR/QUUX/etc.
problem? There seems no solution by the use of
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>...</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>Use an external <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code>, i.e. a program which acts
like a <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code>. It is run once on startup of Apache
receives the requested URLs on <code>STDIN</code> and has
to put the resulting (usually rewritten) URL on
<code>STDOUT</code> (same order!).</p>
<div class="example"><pre>
RewriteEngine on
RewriteMap quux-map <strong>prg:</strong>/path/to/map.quux.pl
RewriteRule ^/~quux/(.*)$ /~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>
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