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<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
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This file is generated from xml source: DO NOT EDIT
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<title>Apache mod_rewrite Introduction - Apache HTTP Server</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
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<script src="../style/scripts/prettify.js" type="text/javascript">
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</script>
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body id="manual-page"><div id="page-header">
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.5</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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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="../">Version 2.5</a> > <a href="./">Rewrite</a></div><div id="page-content"><div id="preamble"><h1>Apache mod_rewrite Introduction</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/rewrite/intro.html" title="English"> en </a> |
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<a href="../fr/rewrite/intro.html" hreflang="fr" rel="alternate" title="Fran<61>ais"> fr </a></p>
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</div>
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<p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
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<a href="../mod/mod_rewrite.html">reference documentation</a>. It
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describes the basic concepts necessary for use of
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<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. Other documents go into greater detail,
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but this doc should help the beginner get their feet wet.
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</p>
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</div>
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<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#introduction">Introduction</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#regex">Regular Expressions</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#rewriterule">RewriteRule Basics</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#flags">Rewrite Flags</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#rewritecond">Rewrite Conditions</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#rewritemap">Rewrite maps</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#htaccess">.htaccess files</a></li>
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</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module documentation</a></li><li><a href="remapping.html">Redirection and remapping</a></li><li><a href="access.html">Controlling access</a></li><li><a href="vhosts.html">Virtual hosts</a></li><li><a href="proxy.html">Proxying</a></li><li><a href="rewritemap.html">Using RewriteMap</a></li><li><a href="advanced.html">Advanced techniques</a></li><li><a href="avoid.html">When not to use mod_rewrite</a></li></ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="introduction" id="introduction">Introduction</a></h2>
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<p>The Apache module <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is a very powerful and
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sophisticated module which provides a way to do URL manipulations. With
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it, you can do nearly all types of URL rewriting that you may need. It
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is, however, somewhat complex, and may be intimidating to the beginner.
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There is also a tendency to treat rewrite rules as magic incantation,
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using them without actually understanding what they do.</p>
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<p>This document attempts to give sufficient background so that what
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follows is understood, rather than just copied blindly.
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</p>
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<p>Remember that many common URL-manipulation tasks don't require the
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full power and complexity of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. For simple
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tasks, see <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> and the documentation
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on <a href="../urlmapping.html">mapping URLs to the
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filesystem</a>.</p>
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<p>Finally, before proceeding, be sure to configure
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<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>'s log level to one of the trace levels using
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the <code class="directive"><a href="../mod/core.html#loglevel">LogLevel</a></code> directive. Although this
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can give an overwhelming amount of information, it is indispensable in
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debugging problems with <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> configuration, since
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it will tell you exactly how each rule is processed.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="regex" id="regex">Regular Expressions</a></h2>
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<p>mod_rewrite uses the <a href="http://pcre.org/">Perl Compatible
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Regular Expression</a> vocabulary. In this document, we do not attempt
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to provide a detailed reference to regular expressions. For that, we
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recommend the <a href="http://pcre.org/pcre.txt">PCRE man pages</a>, the
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<a href="http://perldoc.perl.org/perlre.html">Perl regular
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expression man page</a>, and <a href="http://shop.oreilly.com/product/9780596528126.do">Mastering
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Regular Expressions, by Jeffrey Friedl</a>.</p>
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<p>In this document, we attempt to provide enough of a regex vocabulary
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to get you started, without being overwhelming, in the hope that
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<code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>s will be scientific
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formulae, rather than magical incantations.</p>
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<h3><a name="regexvocab" id="regexvocab">Regex vocabulary</a></h3>
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<p>The following are the minimal building blocks you will need, in order
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to write regular expressions and <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>s. They certainly do not
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represent a complete regular expression vocabulary, but they are a good
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place to start, and should help you read basic regular expressions, as
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well as write your own.</p>
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<table>
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<tr>
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<th>Character</th>
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<th>Meaning</th>
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<th>Example</th>
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</tr>
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<tr><td><code>.</code></td><td>Matches any single
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character</td><td><code>c.t</code> will match <code>cat</code>,
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<code>cot</code>, <code>cut</code>, etc.</td></tr>
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<tr><td><code>+</code></td><td>Repeats the previous match one or more
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times</td><td><code>a+</code> matches <code>a</code>, <code>aa</code>,
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<code>aaa</code>, etc</td></tr>
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<tr><td><code>*</code></td><td>Repeats the previous match zero or more
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times.</td><td><code>a*</code> matches all the same things
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<code>a+</code> matches, but will also match an empty string.</td></tr>
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<tr><td><code>?</code></td><td>Makes the match optional.</td><td>
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<code>colou?r</code> will match <code>color</code> and <code>colour</code>.</td>
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</tr>
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<tr><td><code>^</code></td><td>Called an anchor, matches the beginning
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of the string</td><td><code>^a</code> matches a string that begins with
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<code>a</code></td></tr>
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<tr><td><code>$</code></td><td>The other anchor, this matches the end of
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the string.</td><td><code>a$</code> matches a string that ends with
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<code>a</code>.</td></tr>
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<tr><td><code>( )</code></td><td>Groups several characters into a single
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unit, and captures a match for use in a backreference.</td><td><code>(ab)+</code>
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matches <code>ababab</code> - that is, the <code>+</code> applies to the group.
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For more on backreferences see <a href="#InternalBackRefs">below</a>.</td></tr>
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<tr><td><code>[ ]</code></td><td>A character class - matches one of the
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characters</td><td><code>c[uoa]t</code> matches <code>cut</code>,
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<code>cot</code> or <code>cat</code>.</td></tr>
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<tr><td><code>[^ ]</code></td><td>Negative character class - matches any character not specified</td><td><code>c[^/]t</code> matches <code>cat</code> or <code>c=t</code> but not <code>c/t</code></td></tr>
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</table>
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<p>In <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> the <code>!</code> character can be
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used before a regular expression to negate it. This is, a string will
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be considered to have matched only if it does not match the rest of
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the expression.</p>
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<h3><a name="InternalBackRefs" id="InternalBackRefs">Regex Back-Reference Availability</a></h3>
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<p>One important thing here has to be remembered: Whenever you
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use parentheses in <em>Pattern</em> or in one of the
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<em>CondPattern</em>, back-references are internally created
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which can be used with the strings <code>$N</code> and
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<code>%N</code> (see below). These are available for creating
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the strings <em>Substitution</em> and <em>TestString</em> as
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outlined in the following chapters. Figure 1 shows to which
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locations the back-references are transferred for expansion as
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well as illustrating the flow of the RewriteRule, RewriteCond
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matching. In the next chapters, we will be exploring how to use
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these back-references, so do not fret if it seems a bit alien
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to you at first.
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</p>
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<p class="figure">
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<img src="../images/rewrite_backreferences.png" alt="Flow of RewriteRule and RewriteCond matching" /><br />
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<dfn>Figure 1:</dfn> The back-reference flow through a rule.<br />
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In this example, a request for <code>/test/1234</code> would be transformed into <code>/admin.foo?page=test&id=1234&host=admin.example.com</code>.
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</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="rewriterule" id="rewriterule">RewriteRule Basics</a></h2>
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<p>A <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> consists
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of three arguments separated by spaces. The arguments are</p>
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<ol>
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<li><var>Pattern</var>: which incoming URLs should be affected by the rule;</li>
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<li><var>Substitution</var>: where should the matching requests be sent;</li>
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<li><var>[flags]</var>: options affecting the rewritten request.</li>
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</ol>
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<p>The <var>Pattern</var> is always a <a href="#regex">regular
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expression</a> matched against the URL-Path of the incoming request
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(the part after the hostname but before any question mark indicating
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the beginning of a query string) or, in per-directory context, against
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the request's path relative to the directory for which the rule is
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defined.</p>
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<p class="figure">
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<img src="../images/syntax_rewriterule.png" alt="Syntax of the RewriteRule directive" /><br />
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<dfn>Figure 2:</dfn> Syntax of the RewriteRule directive.
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</p>
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<p>The <var>Substitution</var> can itself be one of three things:</p>
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<dl>
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<dt>A full filesystem path to a resource</dt>
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<dd>
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<pre class="prettyprint lang-config">
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RewriteRule ^/games /usr/local/games/web
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</pre>
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<p>This maps a request to an arbitrary location on your filesystem, much
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like the <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> directive.</p>
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</dd>
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<dt>A web-path to a resource</dt>
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<dd>
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<pre class="prettyprint lang-config">
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RewriteRule ^/foo$ /bar
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</pre>
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<p>If <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code> is set
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to <code>/usr/local/apache2/htdocs</code>, then this directive would
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map requests for <code>http://example.com/foo</code> to the
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path <code>/usr/local/apache2/htdocs/bar</code>.</p>
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</dd>
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<dt>An absolute URL</dt>
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<dd>
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<pre class="prettyprint lang-config">
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RewriteRule ^/product/view$ http://site2.example.com/seeproduct.html [R]
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</pre>
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<p>This tells the client to make a new request for the specified URL.</p>
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</dd>
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</dl>
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<p>The <var>Substitution</var> can also
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contain <em>back-references</em> to parts of the incoming URL-path
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matched by the <var>Pattern</var>. Consider the following:</p>
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<pre class="prettyprint lang-config">
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RewriteRule ^/product/(.*)/view$ /var/web/productdb/$1
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</pre>
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<p>The variable <code>$1</code> will be replaced with whatever text
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was matched by the expression inside the parenthesis in
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the <var>Pattern</var>. For example, a request
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for <code>http://example.com/product/r14df/view</code> will be mapped
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to the path <code>/var/web/productdb/r14df</code>.</p>
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<p>If there is more than one expression in parenthesis, they are
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available in order in the
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variables <code>$1</code>, <code>$2</code>, <code>$3</code>, and so
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on.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="flags" id="flags">Rewrite Flags</a></h2>
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<p>The behavior of a <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> can be modified by the
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application of one or more flags to the end of the rule. For example, the
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matching behavior of a rule can be made case-insensitive by the
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application of the <code>[NC]</code> flag:
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</p>
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<pre class="prettyprint lang-config">
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RewriteRule ^puppy.html smalldog.html [NC]
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</pre>
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<p>For more details on the available flags, their meanings, and
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examples, see the <a href="flags.html">Rewrite Flags</a> document.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="rewritecond" id="rewritecond">Rewrite Conditions</a></h2>
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<p>One or more <code class="directive"><a href="../mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>
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directives can be used to restrict the types of requests that will be
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subject to the
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following <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. The
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first argument is a variable describing a characteristic of the
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request, the second argument is a <a href="#regex">regular
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expression</a> that must match the variable, and a third optional
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argument is a list of flags that modify how the match is evaluated.</p>
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||
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<p class="figure">
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<img src="../images/syntax_rewritecond.png" alt="Syntax of the RewriteCond directive" /><br />
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<dfn>Figure 3:</dfn> Syntax of the RewriteCond directive
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</p>
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<p>For example, to send all requests from a particular IP range to a
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different server, you could use:</p>
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<pre class="prettyprint lang-config">
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RewriteCond %{REMOTE_ADDR} ^10\.2\.
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RewriteRule (.*) http://intranet.example.com$1
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</pre>
|
||
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<p>When more than
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one <code class="directive"><a href="../mod/mod_rewrite.html#rewritecond">RewriteCond</a></code> is
|
||
specified, they must all match for
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the <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> to be
|
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applied. For example, to deny requests that contain the word "hack" in
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||
their query string, unless they also contain a cookie containing
|
||
the word "go", you could use:</p>
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||
<pre class="prettyprint lang-config">
|
||
RewriteCond %{QUERY_STRING} hack
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RewriteCond %{HTTP_COOKIE} !go
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RewriteRule . - [F]
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||
</pre>
|
||
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||
<p>Notice that the exclamation mark specifies a negative match, so the rule is only applied if the cookie does not contain "go".</p>
|
||
|
||
<p>Matches in the regular expressions contained in
|
||
the <code class="directive"><a href="../mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>s can be
|
||
used as part of the <var>Substitution</var> in
|
||
the <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> using the
|
||
variables <code>%1</code>, <code>%2</code>, etc. For example, this
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||
will direct the request to a different directory depending on the
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||
hostname used to access the site:</p>
|
||
<pre class="prettyprint lang-config">
|
||
RewriteCond %{HTTP_HOST} (.*)
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RewriteRule ^/(.*) /sites/%1/$1
|
||
</pre>
|
||
|
||
<p>If the request was for <code>http://example.com/foo/bar</code>,
|
||
then <code>%1</code> would contain <code>example.com</code>
|
||
and <code>$1</code> would contain <code>foo/bar</code>.</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>The <code class="directive"><a href="../mod/mod_rewrite.html#rewritemap">RewriteMap</a></code> directive
|
||
provides a way to call an external function, so to speak, to do your
|
||
rewriting for you. This is discussed in greater detail in the <a href="rewritemap.html">RewriteMap supplementary documentation</a>.</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>Rewriting is typically configured in the main server configuration
|
||
setting (outside any <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> section) or
|
||
inside <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
|
||
containers. This is the easiest way to do rewriting and is
|
||
recommended. It is possible, however, to do rewriting
|
||
inside <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code>
|
||
sections or <a href="../howto/htaccess.html"><code>.htaccess</code>
|
||
files</a> at the expense of some additional complexity. This technique
|
||
is called per-directory rewrites.</p>
|
||
|
||
<p>The main difference with per-server rewrites is that the path
|
||
prefix of the directory containing the <code>.htaccess</code> file is
|
||
stripped before matching in
|
||
the <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. In addition, the <code class="directive"><a href="../mod/mod_rewrite.html#rewritebase">RewriteBase</a></code> should be used to assure the request is properly mapped.</p>
|
||
|
||
</div></div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/rewrite/intro.html" title="English"> en </a> |
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