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authorhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:35:09 -0500
committerhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 01:36:35 -0500
commitcc40af334e619bb549038238507407866f774f8f (patch)
tree43ddc1974f72997a57173151eafb23e6025a13c9 /rubbos/app/apache2/manual/mod/mod_rewrite.html.en
parent68e74fd78b2485e5914ce34a5b30f4485029e021 (diff)
upload apache
JIRA: BOTTLENECK-10 Change-Id: I67eae31de6dc824097dfa56ab454ba36fdd23a2c Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
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+<?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>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>
+<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="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">Modules</a></div>
+<div id="page-content">
+<div id="preamble"><h1>Apache Module mod_rewrite</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/mod/mod_rewrite.html" title="English">&nbsp;en&nbsp;</a></p>
+</div>
+<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Provides a rule-based rewriting engine to rewrite requested
+URLs on the fly</td></tr>
+<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>rewrite_module</td></tr>
+<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_rewrite.c</td></tr>
+<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 1.3 and later</td></tr></table>
+<h3>Summary</h3>
+
+ <p>This module uses a rule-based rewriting engine (based on a
+ regular-expression parser) to rewrite requested URLs on the
+ fly. It supports an unlimited number of rules and an
+ unlimited number of attached rule conditions for each rule, to
+ provide a really flexible and powerful URL manipulation
+ mechanism. The URL manipulations can depend on various tests,
+ of server variables, environment variables, HTTP
+ headers, or time stamps. Even external database lookups in
+ various formats can be used to achieve highly granular URL
+ matching.</p>
+
+ <p>This module operates on the full URLs (including the
+ path-info part) both in per-server context
+ (<code>httpd.conf</code>) and per-directory context
+ (<code>.htaccess</code>) and can generate query-string
+ parts on result. The rewritten result can lead to internal
+ sub-processing, external request redirection or even to an
+ internal proxy throughput.</p>
+
+ <p>Further details, discussion, and examples, are provided in the
+ <a href="../rewrite/">detailed mod_rewrite documentation</a>.</p>
+</div>
+<div id="quickview"><h3 class="directives">Directives</h3>
+<ul id="toc">
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritebase">RewriteBase</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritecond">RewriteCond</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewriteengine">RewriteEngine</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritelock">RewriteLock</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritelog">RewriteLog</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewriteloglevel">RewriteLogLevel</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewritemap">RewriteMap</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewriteoptions">RewriteOptions</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#rewriterule">RewriteRule</a></li>
+</ul>
+<h3>Topics</h3>
+<ul id="topics">
+<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>
+<li><img alt="" src="../images/down.gif" /> <a href="#InternalBackRefs">Regex Back-Reference Availability</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#quoting">Quoting Special Characters</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#EnvVar">Environment Variables</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#Solutions">Practical Solutions</a></li>
+</ul><h3>See also</h3>
+<ul class="seealso">
+<li><a href="#rewriteflags">Rewrite Flags</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="InternalAPI" id="InternalAPI">API Phases</a></h2>
+
+ <p>Apache processes a HTTP request in several phases.
+ A hook for each of these
+ phases is provided by the Apache API. <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> uses two of
+ these hooks: the URL-to-filename translation hook
+ (used after the HTTP request has been read, but before any
+ authorization starts) and the Fixup hook (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>Once a request comes in, and Apache has determined the
+ appropriate server (or virtual server), the rewrite engine
+ starts the URL-to-filename translation,
+ processing the mod_rewrite directives from the
+ per-server configuration. 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. </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>When mod_rewrite is triggered during these two API phases, it
+ reads the relevant rulesets from its configuration
+ structure (which was either created on startup, for
+ per-server context, or during the directory traversal
+ for per-directory context). The URL rewriting
+ engine is started with the appropriate ruleset (one or more
+ rules together with their conditions), and its operation
+ 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
+ rewrite engine processes them in a particular (not always
+ obvious) order, as follows: The rewrite engine loops
+ through the rulesets (each ruleset being made up of <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives, with or without
+ <code class="directive"><a href="#rewritecond">RewriteCond</a></code>s), rule by rule.
+ When a particular rule is matched, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
+ also checks the corresponding conditions (<code>RewriteCond</code>
+ directives). For historical reasons the conditions are given
+ first, making the control flow 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 of the rewrite engine through a
+ rewrite ruleset
+</p>
+ <p>As above, first the URL is matched against the
+ <em>Pattern</em> of a rule. If it does not match, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> immediately stops processing that rule,
+ and goes on to the next rule. If the <em>Pattern</em> matches,
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> checks for rule conditions.
+ If none are present, the URL will be replaced with a new string,
+ constructed from the <em>Substitution</em> string, and <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> goes on to the next rule.</p>
+ <p>If <code class="directive">RewriteCond</code>s exist, an
+ inner loop is started, processing them in the order that they are
+ listed. Conditions are not matched against the current URL directly.
+ A <em>TestString</em> is constructed by expanding variables,
+ back-references, map lookups, etc., against which the
+ <em>CondPattern</em> is matched. If the pattern fails to match one
+ of the conditions, the complete set of rule and associated conditions
+ fails. If the pattern matches a given condition, then matching continues
+ to the next condition, until no more conditions are
+ available. If all conditions match, processing is continued
+ with the substitution of the <em>Substitution</em> string for the URL.</p>
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="InternalBackRefs" id="InternalBackRefs">Regex Back-Reference Availability</a></h2>
+
+ <p>Using parentheses in <em>Pattern</em> or in one of the
+ <em>CondPattern</em>s causes back-references to be internally
+ created.
+ These can later be referenced using the strings <code>$N</code> and
+ <code>%N</code> (see below), for creating
+ the <em>Substitution</em> and <em>TestString</em> strings.
+ Figure 2 attempts to show how the back-references are
+ transferred through the process for later expansion.</p>
+
+<p class="figure">
+ <img src="../images/mod_rewrite_fig2.gif" width="381" height="179" alt="[Needs graphics capability to display]" /><br />
+ <dfn>Figure 2:</dfn> The back-reference flow through a rule.
+</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="quoting" id="quoting">Quoting Special Characters</a></h2>
+
+ <p>As of Apache 1.3.20, special characters in
+ <em>TestString</em> and <em>Substitution</em> strings can be
+ escaped (that is, treated as normal characters without their
+ usual special meaning) by prefixing them with a backslash ('\')
+ character. In other words, you can include an actual
+ dollar-sign character in a <em>Substitution</em> string by
+ using '<code>\$</code>'; this keeps mod_rewrite from trying
+ to treat it as a backreference.</p>
+</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>, that is, <em>before</em> any
+ rewriting. This is important to note because the rewriting process is
+ primarily used to rewrite logical URLs to physical
+ pathnames.</p>
+
+<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 class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="Solutions" id="Solutions">Practical Solutions</a></h2>
+
+ <p>For numerous examples of common, and not-so-common, uses for
+ mod_rewrite, see the <a href="../rewrite/rewrite_guide.html">Rewrite
+ Guide</a>, and the <a href="../rewrite/rewrite_guide_advanced.html">Advanced Rewrite
+ Guide</a> documents.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteBase" id="RewriteBase">RewriteBase</a> <a name="rewritebase" id="rewritebase">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the base URL for per-directory rewrites</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteBase <em>URL-path</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for information.</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+ <p>The <code class="directive">RewriteBase</code> directive explicitly
+ sets the base URL for per-directory rewrites. As you will see
+ below, <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
+ can be used in per-directory config files
+ (<code>.htaccess</code>). In such a case, it will act locally,
+ stripping the local directory prefix before processing, and applying
+ rewrite rules only to the remainder. When processing is complete, the
+ prefix is automatically added back to the
+ path. The default setting is; <code class="directive">RewriteBase</code> <em>physical-directory-path</em></p>
+
+ <p>When a substitution occurs for a new URL, this module has
+ to re-inject the URL into the server processing. To be able
+ to do this it needs to know what the corresponding URL-prefix
+ or URL-base is. By default this prefix is the corresponding
+ filepath itself. <strong>However, for most websites, URLs are NOT
+ directly related to physical filename paths, so this
+ assumption will often be wrong!</strong> Therefore, you can
+ use the <code>RewriteBase</code> directive to specify the
+ correct URL-prefix.</p>
+
+<div class="note"> If your webserver's URLs are <strong>not</strong> directly
+related to physical file paths, you will need to use
+<code class="directive">RewriteBase</code> in every <code>.htaccess</code>
+file where you want to use <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives.
+</div>
+
+ <p> For example, assume the following per-directory config file:</p>
+
+<div class="example"><pre>
+#
+# /abc/def/.htaccess -- per-dir config file for directory /abc/def
+# Remember: /abc/def is the physical path of /xyz, <em>i.e.</em>, the server
+# has a 'Alias /xyz /abc/def' directive <em>e.g.</em>
+#
+
+RewriteEngine On
+
+# let the server know that we were reached via /xyz and not
+# via the physical path prefix /abc/def
+RewriteBase /xyz
+
+# now the rewriting rules
+RewriteRule ^oldstuff\.html$ newstuff.html
+</pre></div>
+
+ <p>In the above example, a request to
+ <code>/xyz/oldstuff.html</code> gets correctly rewritten to
+ the physical file <code>/abc/def/newstuff.html</code>.</p>
+
+<div class="note"><h3>For Apache Hackers</h3>
+<p>The following list gives detailed information about
+ the internal processing steps:</p>
+<pre>
+Request:
+ /xyz/oldstuff.html
+
+Internal Processing:
+ /xyz/oldstuff.html -&gt; /abc/def/oldstuff.html (per-server Alias)
+ /abc/def/oldstuff.html -&gt; /abc/def/newstuff.html (per-dir RewriteRule)
+ /abc/def/newstuff.html -&gt; /xyz/newstuff.html (per-dir RewriteBase)
+ /xyz/newstuff.html -&gt; /abc/def/newstuff.html (per-server Alias)
+
+Result:
+ /abc/def/newstuff.html
+</pre>
+ <p>This seems very complicated, but is in fact
+ correct Apache internal processing. Because the
+ per-directory rewriting comes late in the
+ process, the rewritten request
+ has to be re-injected into the Apache kernel, as if it
+ were a new request. (See <a href="../rewrite/rewrite_tech.html">mod_rewrite technical
+ details</a>.)
+ This is not the serious overhead it may seem to be -
+ this re-injection is completely internal to the
+ Apache server (and the same procedure is used by
+ many other operations within Apache).</p>
+</div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteCond" id="RewriteCond">RewriteCond</a> <a name="rewritecond" id="rewritecond">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines a condition under which rewriting will take place
+</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code> RewriteCond
+ <em>TestString</em> <em>CondPattern</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+ <p>The <code class="directive">RewriteCond</code> directive defines a
+ rule condition. One or more <code class="directive">RewriteCond</code>
+ can precede a <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
+ directive. The following rule is then only used if both
+ the current state of the URI matches its pattern, <strong>and</strong> if these conditions are met.</p>
+
+ <p><em>TestString</em> is a string which can contain the
+ following expanded constructs in addition to plain text:</p>
+
+ <ul>
+ <li>
+ <strong>RewriteRule backreferences</strong>: These are
+ backreferences of the form <strong><code>$N</code></strong>
+ (0 &lt;= N &lt;= 9), which provide access to the grouped
+ parts (in parentheses) of the pattern, from the
+ <code>RewriteRule</code> which is subject to the current
+ set of <code>RewriteCond</code> conditions..
+ </li>
+ <li>
+ <strong>RewriteCond backreferences</strong>: These are
+ backreferences of the form <strong><code>%N</code></strong>
+ (1 &lt;= N &lt;= 9), which provide access to the grouped
+ parts (again, in parentheses) of the pattern, from the last matched
+ <code>RewriteCond</code> in the current set
+ of conditions.
+ </li>
+ <li>
+ <strong>RewriteMap expansions</strong>: These are
+ expansions of the form <strong><code>${mapname:key|default}</code></strong>.
+ See <a href="#mapfunc">the documentation for
+ RewriteMap</a> for more details.
+ </li>
+ <li>
+ <strong>Server-Variables</strong>: These are variables of
+ the form
+ <strong><code>%{</code> <em>NAME_OF_VARIABLE</em>
+ <code>}</code></strong>
+ where <em>NAME_OF_VARIABLE</em> can be a string taken
+ from the following list:
+
+ <table>
+
+ <tr>
+ <th>HTTP headers:</th> <th>connection &amp; request:</th> <th />
+ </tr>
+
+ <tr>
+ <td>
+ HTTP_USER_AGENT<br />
+ HTTP_REFERER<br />
+ HTTP_COOKIE<br />
+ HTTP_FORWARDED<br />
+ HTTP_HOST<br />
+ HTTP_PROXY_CONNECTION<br />
+ HTTP_ACCEPT<br />
+ </td>
+
+ <td>
+ REMOTE_ADDR<br />
+ REMOTE_HOST<br />
+ REMOTE_PORT<br />
+ REMOTE_USER<br />
+ REMOTE_IDENT<br />
+ REQUEST_METHOD<br />
+ SCRIPT_FILENAME<br />
+ PATH_INFO<br />
+ QUERY_STRING<br />
+ AUTH_TYPE<br />
+ </td>
+
+ <td />
+ </tr>
+
+ <tr>
+ <th>server internals:</th> <th>system stuff:</th> <th>specials:</th>
+ </tr>
+
+ <tr>
+ <td>
+ DOCUMENT_ROOT<br />
+ SERVER_ADMIN<br />
+ SERVER_NAME<br />
+ SERVER_ADDR<br />
+ SERVER_PORT<br />
+ SERVER_PROTOCOL<br />
+ SERVER_SOFTWARE<br />
+ </td>
+
+ <td>
+ TIME_YEAR<br />
+ TIME_MON<br />
+ TIME_DAY<br />
+ TIME_HOUR<br />
+ TIME_MIN<br />
+ TIME_SEC<br />
+ TIME_WDAY<br />
+ TIME<br />
+ </td>
+
+ <td>
+ API_VERSION<br />
+ THE_REQUEST<br />
+ REQUEST_URI<br />
+ REQUEST_FILENAME<br />
+ IS_SUBREQ<br />
+ HTTPS<br />
+ </td>
+ </tr>
+ </table>
+
+ <p>These variables all
+ correspond to the similarly named HTTP
+ MIME-headers, C variables of the Apache server or
+ <code>struct tm</code> fields of the Unix system.
+ Most are documented elsewhere in the Manual or in
+ the CGI specification. Those that are special to
+ mod_rewrite include those below.</p>
+ <div class="note">
+ <dl>
+ <dt><code>IS_SUBREQ</code></dt>
+
+ <dd>Will contain the text "true" if the request
+ currently being processed is a sub-request,
+ "false" otherwise. Sub-requests may be generated
+ by modules that need to resolve additional files
+ or URIs in order to complete their tasks.</dd>
+
+ <dt><code>API_VERSION</code></dt>
+
+ <dd>This is the version of the Apache module API
+ (the internal interface between server and
+ module) in the current httpd build, as defined in
+ include/ap_mmn.h. The module API version
+ corresponds to the version of Apache in use (in
+ the release version of Apache 1.3.14, for
+ instance, it is 19990320:10), but is mainly of
+ interest to module authors.</dd>
+
+ <dt><code>THE_REQUEST</code></dt>
+
+ <dd>The full HTTP request line sent by the
+ browser to the server (e.g., "<code>GET
+ /index.html HTTP/1.1</code>"). This does not
+ include any additional headers sent by the
+ browser.</dd>
+
+ <dt><code>REQUEST_URI</code></dt>
+
+ <dd>The resource requested in the HTTP request
+ line. (In the example above, this would be
+ "/index.html".)</dd>
+
+ <dt><code>REQUEST_FILENAME</code></dt>
+
+ <dd>The full local filesystem path to the file or
+ script matching the request.</dd>
+
+ <dt><code>HTTPS</code></dt>
+
+ <dd>Will contain the text "on" if the connection is
+ using SSL/TLS, or "off" otherwise. (This variable
+ can be safely used regardless of whether or not
+ <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is loaded).</dd>
+
+ </dl>
+</div>
+ </li>
+ </ul>
+
+ <p>Other things you should be aware of:</p>
+
+ <ol>
+ <li>The variables SCRIPT_FILENAME and REQUEST_FILENAME
+ contain the same value - the value of the
+ <code>filename</code> field of the internal
+ <code>request_rec</code> structure of the Apache server.
+ The first name is the commonly known CGI variable name
+ while the second is the appropriate counterpart of
+ REQUEST_URI (which contains the value of the
+ <code>uri</code> field of <code>request_rec</code>).</li>
+
+ <li>
+ <code>%{ENV:variable}</code>, where <em>variable</em> can be
+ any environment variable, is also available.
+ This is looked-up via internal
+ Apache structures and (if not found there) via
+ <code>getenv()</code> from the Apache server process.</li>
+
+ <li>
+ <code>%{SSL:variable}</code>, where <em>variable</em> is the
+ name of an <a href="mod_ssl.html#envvars">SSL environment
+ variable</a>, can be used whether or not
+ <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is loaded, but will always expand to
+ the empty string if it is not. Example:
+ <code>%{SSL:SSL_CIPHER_USEKEYSIZE}</code> may expand to
+ <code>128</code>.</li>
+
+ <li>
+ <code>%{HTTP:header}</code>, where <em>header</em> can be
+ any HTTP MIME-header name, can always be used to obtain the
+ value of a header sent in the HTTP request.
+ Example: <code>%{HTTP:Proxy-Connection}</code> is
+ the value of the HTTP header
+ ``<code>Proxy-Connection:</code>''.</li>
+
+ <li>
+ <code>%{LA-U:variable}</code> can be used for look-aheads which perform
+ an internal (URL-based) sub-request to determine the final
+ value of <em>variable</em>. This can be used to access
+ variable for rewriting which is not available at the current
+ stage, but will be set in a later phase.
+ <p>For instance, to rewrite according to the
+ <code>REMOTE_USER</code> variable from within the
+ per-server context (<code>httpd.conf</code> file) you must
+ use <code>%{LA-U:REMOTE_USER}</code> - this
+ variable is set by the authorization phases, which come
+ <em>after</em> the URL translation phase (during which mod_rewrite
+ operates).</p>
+ <p>On the other hand, because mod_rewrite implements
+ its per-directory context (<code>.htaccess</code> file) via
+ the Fixup phase of the API and because the authorization
+ phases come <em>before</em> this phase, you just can use
+ <code>%{REMOTE_USER}</code> in that context.</p></li>
+
+ <li>
+ <code>%{LA-F:variable}</code> can be used to perform an internal
+ (filename-based) sub-request, to determine the final value
+ of <em>variable</em>. Most of the time, this is the same as
+ LA-U above.</li>
+ </ol>
+
+ <p><em>CondPattern</em> is the condition pattern,
+ a regular expression which is applied to the
+ current instance of the <em>TestString</em>.
+ <em>TestString</em> is first evaluated, before being matched against
+ <em>CondPattern</em>.</p>
+
+ <p><strong>Remember:</strong> <em>CondPattern</em> is a
+ <em>perl compatible regular expression</em> with some
+ additions:</p>
+
+ <ol>
+ <li>You can prefix the pattern string with a
+ '<code>!</code>' character (exclamation mark) to specify a
+ <strong>non</strong>-matching pattern.</li>
+
+ <li>
+ There are some special variants of <em>CondPatterns</em>.
+ Instead of real regular expression strings you can also
+ use one of the following:
+
+ <ul>
+
+ <li>'<strong>&lt;CondPattern</strong>' (lexicographically
+ precedes)<br />
+ Treats the <em>CondPattern</em> as a plain string and
+ compares it lexicographically to <em>TestString</em>. True if
+ <em>TestString</em> lexicographically precedes
+ <em>CondPattern</em>.</li>
+
+ <li>'<strong>&gt;CondPattern</strong>' (lexicographically
+ follows)<br />
+ Treats the <em>CondPattern</em> as a plain string and
+ compares it lexicographically to <em>TestString</em>. True if
+ <em>TestString</em> lexicographically follows
+ <em>CondPattern</em>.</li>
+
+ <li>'<strong>=CondPattern</strong>' (lexicographically
+ equal)<br />
+ Treats the <em>CondPattern</em> as a plain string and
+ compares it lexicographically to <em>TestString</em>. True if
+ <em>TestString</em> is lexicographically equal to
+ <em>CondPattern</em> (the two strings are exactly
+ equal, character for character). If <em>CondPattern</em>
+ is <code>""</code> (two quotation marks) this
+ compares <em>TestString</em> to the empty string.</li>
+
+ <li>'<strong>-d</strong>' (is
+ <strong>d</strong>irectory)<br />
+ Treats the <em>TestString</em> as a pathname and tests
+ whether or not it exists, and is a directory.</li>
+
+ <li>'<strong>-f</strong>' (is regular
+ <strong>f</strong>ile)<br />
+ Treats the <em>TestString</em> as a pathname and tests
+ whether or not it exists, and is a regular file.</li>
+
+ <li>'<strong>-s</strong>' (is regular file, with
+ <strong>s</strong>ize)<br />
+ Treats the <em>TestString</em> as a pathname and tests
+ whether or not it exists, and is a regular file with size greater
+ than zero.</li>
+
+ <li>'<strong>-l</strong>' (is symbolic
+ <strong>l</strong>ink)<br />
+ Treats the <em>TestString</em> as a pathname and tests
+ whether or not it exists, and is a symbolic link.</li>
+
+ <li>'<strong>-F</strong>' (is existing file, via
+ subrequest)<br />
+ Checks whether or not <em>TestString</em> is a valid file,
+ accessible via all the server's currently-configured
+ access controls for that path. This uses an internal
+ subrequest to do the check, so use it with care -
+ it can impact your server's performance!</li>
+
+ <li>'<strong>-U</strong>' (is existing URL, via
+ subrequest)<br />
+ Checks whether or not <em>TestString</em> is a valid URL,
+ accessible via all the server's currently-configured
+ access controls for that path. This uses an internal
+ subrequest to do the check, so use it with care -
+ it can impact your server's performance!</li>
+ </ul>
+
+<div class="note"><h3>Note</h3>
+ All of these tests can
+ also be prefixed by an exclamation mark ('!') to
+ negate their meaning.
+</div>
+ </li>
+
+ <li>You can also set special flags for
+ <em>CondPattern</em> by appending
+ <strong><code>[</code><em>flags</em><code>]</code></strong>
+ as the third argument to the <code>RewriteCond</code>
+ directive, where <em>flags</em> is a comma-separated list of any of the
+ following flags:
+
+ <ul>
+ <li>'<strong><code>nocase|NC</code></strong>'
+ (<strong>n</strong>o <strong>c</strong>ase)<br />
+ This makes the test case-insensitive - differences
+ between 'A-Z' and 'a-z' are ignored, both in the
+ expanded <em>TestString</em> and the <em>CondPattern</em>.
+ This flag is effective only for comparisons between
+ <em>TestString</em> and <em>CondPattern</em>. It has no
+ effect on filesystem and subrequest checks.</li>
+
+ <li>
+ '<strong><code>ornext|OR</code></strong>'
+ (<strong>or</strong> next condition)<br />
+ Use this to combine rule conditions with a local OR
+ instead of the implicit AND. Typical example:
+
+<div class="example"><pre>
+RewriteCond %{REMOTE_HOST} ^host1.* [OR]
+RewriteCond %{REMOTE_HOST} ^host2.* [OR]
+RewriteCond %{REMOTE_HOST} ^host3.*
+RewriteRule ...some special stuff for any of these hosts...
+</pre></div>
+
+ Without this flag you would have to write the condition/rule
+ pair three times.
+ </li>
+ </ul>
+ </li>
+ </ol>
+
+ <p><strong>Example:</strong></p>
+
+ <p>To rewrite the Homepage of a site according to the
+ ``<code>User-Agent:</code>'' header of the request, you can
+ use the following: </p>
+
+<div class="example"><pre>
+RewriteCond %{HTTP_USER_AGENT} ^Mozilla.*
+RewriteRule ^/$ /homepage.max.html [L]
+
+RewriteCond %{HTTP_USER_AGENT} ^Lynx.*
+RewriteRule ^/$ /homepage.min.html [L]
+
+RewriteRule ^/$ /homepage.std.html [L]
+</pre></div>
+
+ <p>Explanation: If you use a browser which identifies itself
+ as 'Mozilla' (including Netscape Navigator, Mozilla etc), then you
+ get the max homepage (which could include frames, or other special
+ features).
+ If you use the Lynx browser (which is terminal-based), then
+ you get the min homepage (which could be a version designed for
+ easy, text-only browsing).
+ If neither of these conditions apply (you use any other browser,
+ or your browser identifies itself as something non-standard), you get
+ the std (standard) homepage.</p>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteEngine" id="RewriteEngine">RewriteEngine</a> <a name="rewriteengine" id="rewriteengine">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables or disables runtime rewriting engine</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteEngine on|off</code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>RewriteEngine off</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+
+ <p>The <code class="directive">RewriteEngine</code> directive enables or
+ disables the runtime rewriting engine. If it is set to
+ <code>off</code> this module does no runtime processing at
+ all. It does not even update the <code>SCRIPT_URx</code>
+ environment variables.</p>
+
+ <p>Use this directive to disable the module instead of
+ commenting out all the <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives!</p>
+
+ <p>Note that, by default, rewrite configurations are not
+ inherited. This means that you need to have a
+ <code>RewriteEngine on</code> directive for each virtual host
+ in which you wish to use it.</p>
+
+ <p><code class="directive">RewriteMap</code> directives of the type <code>prg</code>
+ are not started during server initialization if they're defined in a
+ context that does not have <code class="directive">RewriteEngine</code> set to
+ <code>on</code></p>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteLock" id="RewriteLock">RewriteLock</a> <a name="rewritelock" id="rewritelock">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the name of the lock file used for <code class="directive"><a href="#rewritemap">RewriteMap</a></code>
+synchronization</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteLock <em>file-path</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+ <p>This directive sets the filename for a synchronization
+ lockfile which mod_rewrite needs to communicate with <code class="directive"><a href="#rewritemap">RewriteMap</a></code>
+ <em>programs</em>. Set this lockfile to a local path (not on a
+ NFS-mounted device) when you want to use a rewriting
+ map-program. It is not required for other types of rewriting
+ maps.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteLog" id="RewriteLog">RewriteLog</a> <a name="rewritelog" id="rewritelog">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the name of the file used for logging rewrite engine
+processing</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteLog <em>file-path</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+ <p>The <code class="directive">RewriteLog</code> directive sets the name
+ of the file to which the server logs any rewriting actions it
+ performs. If the name does not begin with a slash
+ ('<code>/</code>') then it is assumed to be relative to the
+ <em>Server Root</em>. The directive should occur only once per
+ server config.</p>
+
+<div class="note"> To disable the logging of
+ rewriting actions it is not recommended to set
+ <em>Filename</em> to <code>/dev/null</code>, because
+ although the rewriting engine does not then output to a
+ logfile it still creates the logfile output internally.
+ <strong>This will slow down the server with no advantage
+ to the administrator!</strong> To disable logging either
+ remove or comment out the <code class="directive">RewriteLog</code>
+ directive or use <code>RewriteLogLevel 0</code>!
+</div>
+
+<div class="note"><h3>Security</h3>
+
+See the <a href="../misc/security_tips.html">Apache Security Tips</a>
+document for details on how your security could be compromised if the
+directory where logfiles are stored is writable by anyone other than
+the user that starts the server.
+</div>
+
+<div class="example"><h3>Example</h3><p><code>
+RewriteLog "/usr/local/var/apache/logs/rewrite.log"
+</code></p></div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteLogLevel" id="RewriteLogLevel">RewriteLogLevel</a> <a name="rewriteloglevel" id="rewriteloglevel">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the verbosity of the log file used by the rewrite
+engine</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteLogLevel <em>Level</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>RewriteLogLevel 0</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+</table>
+ <p>The <code class="directive">RewriteLogLevel</code> directive sets the
+ verbosity level of the rewriting logfile. The default level 0
+ means no logging, while 9 or more means that practically all
+ actions are logged.</p>
+
+ <p>To disable the logging of rewriting actions simply set
+ <em>Level</em> to 0. This disables all rewrite action
+ logs.</p>
+
+<div class="note"> Using a high value for
+ <em>Level</em> will slow down your Apache server
+ dramatically! Use the rewriting logfile at a
+ <em>Level</em> greater than 2 only for debugging!
+</div>
+
+<div class="example"><h3>Example</h3><p><code>
+RewriteLogLevel 3
+</code></p></div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteMap" id="RewriteMap">RewriteMap</a> <a name="rewritemap" id="rewritemap">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines a mapping function for key-lookup</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteMap <em>MapName</em> <em>MapType</em>:<em>MapSource</em>
+</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The choice of different dbm types is available in
+Apache 2.0.41 and later</td></tr>
+</table>
+ <p>The <code class="directive">RewriteMap</code> directive defines a
+ <em>Rewriting Map</em> which can be used inside rule
+ substitution strings by the mapping-functions to
+ insert/substitute fields through a key lookup. The source of
+ this lookup can be of various types.</p>
+
+ <p>The <a id="mapfunc" name="mapfunc"><em>MapName</em></a> is
+ the name of the map and will be used to specify a
+ mapping-function for the substitution strings of a rewriting
+ rule via one of the following constructs:</p>
+
+ <p class="indent">
+ <strong><code>${</code> <em>MapName</em> <code>:</code>
+ <em>LookupKey</em> <code>}</code><br />
+ <code>${</code> <em>MapName</em> <code>:</code>
+ <em>LookupKey</em> <code>|</code> <em>DefaultValue</em>
+ <code>}</code></strong>
+ </p>
+
+ <p>When such a construct occurs, the map <em>MapName</em> is
+ consulted and the key <em>LookupKey</em> is looked-up. If the
+ key is found, the map-function construct is substituted by
+ <em>SubstValue</em>. If the key is not found then it is
+ substituted by <em>DefaultValue</em> or by the empty string
+ if no <em>DefaultValue</em> was specified.</p>
+
+ <p>For example, you might define a
+ <code class="directive">RewriteMap</code> as:</p>
+
+ <div class="example"><p><code>
+ RewriteMap examplemap txt:/path/to/file/map.txt
+ </code></p></div>
+
+ <p>You would then be able to use this map in a
+ <code class="directive">RewriteRule</code> as follows:</p>
+
+ <div class="example"><p><code>
+ RewriteRule ^/ex/(.*) ${examplemap:$1}
+ </code></p></div>
+
+ <p>The following combinations for <em>MapType</em> and
+ <em>MapSource</em> can be used:</p>
+
+ <ul>
+ <li>
+ <strong>Standard Plain Text</strong><br />
+ MapType: <code>txt</code>, MapSource: Unix filesystem
+ path to valid regular file
+
+ <p>This is the standard rewriting map feature where the
+ <em>MapSource</em> is a plain ASCII file containing
+ either blank lines, comment lines (starting with a '#'
+ character) or pairs like the following - one per
+ line.</p>
+
+ <p class="indent">
+ <strong><em>MatchingKey</em>
+ <em>SubstValue</em></strong>
+ </p>
+
+<div class="example"><h3>Example</h3><pre>
+##
+## map.txt -- rewriting map
+##
+
+Ralf.S.Engelschall rse # Bastard Operator From Hell
+Mr.Joe.Average joe # Mr. Average
+</pre></div>
+
+<div class="example"><p><code>
+RewriteMap real-to-user txt:/path/to/file/map.txt
+</code></p></div>
+ </li>
+
+ <li>
+ <strong>Randomized Plain Text</strong><br />
+ MapType: <code>rnd</code>, MapSource: Unix filesystem
+ path to valid regular file
+
+ <p>This is identical to the Standard Plain Text variant
+ above but with a special post-processing feature: After
+ looking up a value it is parsed according to contained
+ ``<code>|</code>'' characters which have the meaning of
+ ``or''. In other words they indicate a set of
+ alternatives from which the actual returned value is
+ chosen randomly. For example, you might use the following map
+ file and directives to provide a random load balancing between
+ several back-end server, via a reverse-proxy. Images are sent
+ to one of the servers in the 'static' pool, while everything
+ else is sent to one of the 'dynamic' pool.</p>
+ <p>Example:</p>
+
+<div class="example"><h3>Rewrite map file</h3><pre>
+##
+## map.txt -- rewriting map
+##
+
+static www1|www2|www3|www4
+dynamic www5|www6
+</pre></div>
+
+<div class="example"><h3>Configuration directives</h3><p><code>
+RewriteMap servers rnd:/path/to/file/map.txt<br />
+<br />
+RewriteRule ^/(.*\.(png|gif|jpg)) http://${servers:static}/$1
+[NC,P,L]<br />
+RewriteRule ^/(.*) http://${servers:dynamic}/$1 [P,L]
+</code></p></div>
+ </li>
+
+ <li>
+ <strong>Hash File</strong><br /> MapType:
+ <code>dbm[=<em>type</em>]</code>, MapSource: Unix filesystem
+ path to valid regular file
+
+ <p>Here the source is a binary format DBM file containing
+ the same contents as a <em>Plain Text</em> format file, but
+ in a special representation which is optimized for really
+ fast lookups. The <em>type</em> can be sdbm, gdbm, ndbm, or
+ db depending on <a href="../install.html#dbm">compile-time
+ settings</a>. If the <em>type</em> is ommitted, the
+ compile-time default will be chosen. You can create such a
+ file with any DBM tool or with the following Perl
+ script. Be sure to adjust it to create the appropriate
+ type of DBM. The example creates an NDBM file.</p>
+
+<div class="example"><pre>
+#!/path/to/bin/perl
+##
+## txt2dbm -- convert txt map to dbm format
+##
+
+use NDBM_File;
+use Fcntl;
+
+($txtmap, $dbmmap) = @ARGV;
+
+open(TXT, "&lt;$txtmap") or die "Couldn't open $txtmap!\n";
+tie (%DB, 'NDBM_File', $dbmmap,O_RDWR|O_TRUNC|O_CREAT, 0644)
+ or die "Couldn't create $dbmmap!\n";
+
+while (&lt;TXT&gt;) {
+ next if (/^\s*#/ or /^\s*$/);
+ $DB{$1} = $2 if (/^\s*(\S+)\s+(\S+)/);
+}
+
+untie %DB;
+close(TXT);
+</pre></div>
+
+<div class="example"><p><code>
+$ txt2dbm map.txt map.db
+</code></p></div>
+ </li>
+
+ <li>
+ <strong>Internal Function</strong><br />
+ MapType: <code>int</code>, MapSource: Internal Apache
+ function
+
+ <p>Here, the source is an internal Apache function.
+ Currently you cannot create your own, but the following
+ functions already exist:</p>
+
+ <ul>
+ <li><strong>toupper</strong>:<br />
+ Converts the key to all upper case.</li>
+
+ <li><strong>tolower</strong>:<br />
+ Converts the key to all lower case.</li>
+
+ <li><strong>escape</strong>:<br />
+ Translates special characters in the key to
+ hex-encodings.</li>
+
+ <li><strong>unescape</strong>:<br />
+ Translates hex-encodings in the key back to
+ special characters.</li>
+ </ul>
+ </li>
+
+ <li>
+ <strong>External Rewriting Program</strong><br />
+ MapType: <code>prg</code>, MapSource: Unix filesystem
+ path to valid regular file
+
+ <p>Here the source is a program, not a map file. To
+ create it you can use a language of your choice, but
+ the result has to be an executable program (either
+ object-code or a script with the magic cookie trick
+ '<code>#!/path/to/interpreter</code>' as the first
+ line).</p>
+
+ <p>This program is started once, when the Apache server
+ is started, and then communicates with the rewriting engine
+ via its <code>stdin</code> and <code>stdout</code>
+ file-handles. For each map-function lookup it will
+ receive the key to lookup as a newline-terminated string
+ on <code>stdin</code>. It then has to give back the
+ looked-up value as a newline-terminated string on
+ <code>stdout</code> or the four-character string
+ ``<code>NULL</code>'' if it fails (<em>i.e.</em>, there
+ is no corresponding value for the given key). A trivial
+ program which will implement a 1:1 map (<em>i.e.</em>,
+ key == value) could be:</p>
+
+ <p>External rewriting programs are not started if they're defined in a
+ context that does not have <code class="directive">RewriteEngine</code> set to
+ <code>on</code></p>.
+
+<div class="example"><pre>
+#!/usr/bin/perl
+$| = 1;
+while (&lt;STDIN&gt;) {
+ # ...put here any transformations or lookups...
+ print $_;
+}
+</pre></div>
+
+ <p>But be very careful:</p>
+
+ <ol>
+ <li>``<em>Keep it simple, stupid</em>'' (KISS).
+ If this program hangs, it will cause Apache to hang
+ when trying to use the relevant rewrite rule.</li>
+
+ <li>A common mistake is to use buffered I/O on
+ <code>stdout</code>. Avoid this, as it will cause a deadloop!
+ ``<code>$|=1</code>'' is used above, to prevent this.</li>
+
+ <li>The <code class="directive"><a href="#rewritelock">RewriteLock</a></code> directive can
+ be used to define a lockfile which mod_rewrite can use to synchronize
+ communication with the mapping program. By default no such
+ synchronization takes place.</li>
+ </ol>
+ </li>
+ </ul>
+ <p>The <code class="directive">RewriteMap</code> directive can occur more than
+ once. For each mapping-function use one
+ <code class="directive">RewriteMap</code> directive to declare its rewriting
+ mapfile. While you cannot <strong>declare</strong> a map in
+ per-directory context it is of course possible to
+ <strong>use</strong> this map in per-directory context. </p>
+
+<div class="note"><h3>Note</h3> For plain text and DBM format files the
+looked-up keys are cached in-core until the <code>mtime</code> of the
+mapfile changes or the server does a restart. This way you can have
+map-functions in rules which are used for <strong>every</strong>
+request. This is no problem, because the external lookup only happens
+once!
+</div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteOptions" id="RewriteOptions">RewriteOptions</a> <a name="rewriteoptions" id="rewriteoptions">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets some special options for the rewrite engine</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteOptions <var>Options</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>RewriteOptions MaxRedirects=10</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td><code>MaxRedirects</code> is available in Apache 2.0.45 and
+later</td></tr>
+</table>
+
+ <p>The <code class="directive">RewriteOptions</code> directive sets some
+ special options for the current per-server or per-directory
+ configuration. The <em>Option</em> strings can be one of the
+ following:</p>
+
+ <dl>
+ <dt><code>inherit</code></dt>
+ <dd>This forces the current configuration to inherit the
+ configuration of the parent. In per-virtual-server context
+ this means that the maps, conditions and rules of the main
+ server are inherited. In per-directory context this means
+ that conditions and rules of the parent directory's
+ <code>.htaccess</code> configuration are inherited.</dd>
+
+ <dt><code>MaxRedirects=<var>number</var></code></dt>
+ <dd>In order to prevent endless loops of internal redirects
+ issued by per-directory <code class="directive"><a href="#rewriterule">RewriteRule</a></code>s, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> aborts
+ the request after reaching a maximum number of such redirects and
+ responds with an 500 Internal Server Error. If you really need
+ more internal redirects than 10 per request, you may increase
+ the default to the desired value.</dd>
+ </dl>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="RewriteRule" id="RewriteRule">RewriteRule</a> <a name="rewriterule" id="rewriterule">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Defines rules for the rewriting engine</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RewriteRule
+ <em>Pattern</em> <em>Substitution</em></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_rewrite</td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The cookie-flag is available in Apache 2.0.40 and later.</td></tr>
+</table>
+ <p>The <code class="directive">RewriteRule</code> directive is the real
+ rewriting workhorse. The directive can occur more than once, with
+ each instance defining a single rewrite rule. The
+ order in which these rules are defined is important - this is the order
+ in which they will be applied at run-time.</p>
+
+ <p><a id="patterns" name="patterns"><em>Pattern</em></a> is
+ a perl compatible <a id="regexp" name="regexp">regular
+ expression</a>, which is applied to the current URL.
+ ``Current'' means the value of the URL when this rule is
+ applied. This may not be the originally requested URL,
+ which may already have matched a previous rule, and have
+ been altered.</p>
+
+ <p>Some hints on the syntax of regular expressions:</p>
+
+<div class="note"><pre>
+<strong>Text:</strong>
+ <strong><code>.</code></strong> Any single character
+ <strong><code>[</code></strong>chars<strong><code>]</code></strong> Character class: Any character of the class ``chars''
+ <strong><code>[^</code></strong>chars<strong><code>]</code></strong> Character class: Not a character of the class ``chars''
+ text1<strong><code>|</code></strong>text2 Alternative: text1 or text2
+
+<strong>Quantifiers:</strong>
+ <strong><code>?</code></strong> 0 or 1 occurrences of the preceding text
+ <strong><code>*</code></strong> 0 or N occurrences of the preceding text (N &gt; 0)
+ <strong><code>+</code></strong> 1 or N occurrences of the preceding text (N &gt; 1)
+
+<strong>Grouping:</strong>
+ <strong><code>(</code></strong>text<strong><code>)</code></strong> Grouping of text
+ (used either to set the borders of an alternative as above, or
+ to make backreferences, where the <strong>N</strong>th group can
+ be referred to on the RHS of a RewriteRule as <code>$</code><strong>N</strong>)
+
+<strong>Anchors:</strong>
+ <strong><code>^</code></strong> Start-of-line anchor
+ <strong><code>$</code></strong> End-of-line anchor
+
+<strong>Escaping:</strong>
+ <strong><code>\</code></strong>char escape the given char
+ (for instance, to specify the chars "<code>.[]()</code>" <em>etc.</em>)
+</pre></div>
+
+ <p>For more information about regular expressions, have a look at the
+ perl regular expression manpage ("<a href="http://perldoc.perl.org/perlre.html">perldoc
+ perlre</a>"). If you are interested in more detailed
+ information about regular expressions and their variants
+ (POSIX regex etc.) the following book is dedicated to this topic:</p>
+
+ <p class="indent">
+ <em>Mastering Regular Expressions, 2nd Edition</em><br />
+ Jeffrey E.F. Friedl<br />
+ O'Reilly &amp; Associates, Inc. 2002<br />
+ ISBN 0-596-00289-0<br />
+ </p>
+
+ <p>In mod_rewrite, the NOT character
+ ('<code>!</code>') is also available as a possible pattern
+ prefix. This enables you to negate a pattern; to say, for instance:
+ ``<em>if the current URL does <strong>NOT</strong> match this
+ pattern</em>''. This can be used for exceptional cases, where
+ it is easier to match the negative pattern, or as a last
+ default rule.</p>
+
+<div class="note"><h3>Note</h3>
+When using the NOT character to negate a pattern, you cannot include
+grouped wildcard parts in that pattern. This is because, when the
+pattern does NOT match (ie, the negation matches), there are no
+contents for the groups. Thus, if negated patterns are used, you
+cannot use <code>$N</code> in the substitution string!
+</div>
+
+ <p>The <a id="rhs" name="rhs"><em>substitution</em></a> of a
+ rewrite rule is the string which is substituted for (or
+ replaces) the original URL which <em>Pattern</em>
+ matched. In addition to plain text, it can include</p>
+
+ <ol>
+ <li>back-references (<code>$N</code>) to the RewriteRule
+ pattern</li>
+
+ <li>back-references (<code>%N</code>) to the last matched
+ RewriteCond pattern</li>
+
+ <li>server-variables as in rule condition test-strings
+ (<code>%{VARNAME}</code>)</li>
+
+ <li><a href="#mapfunc">mapping-function</a> calls
+ (<code>${mapname:key|default}</code>)</li>
+ </ol>
+
+ <p>Back-references are identifiers of the form
+ <code>$</code><strong>N</strong>
+ (<strong>N</strong>=0..9), which will be replaced
+ by the contents of the <strong>N</strong>th group of the
+ matched <em>Pattern</em>. The server-variables are the same
+ as for the <em>TestString</em> of a <code>RewriteCond</code>
+ directive. The mapping-functions come from the
+ <code>RewriteMap</code> directive and are explained there.
+ These three types of variables are expanded in the order above.</p>
+
+ <p>As already mentioned, all rewrite rules are
+ applied to the <em>Substitution</em> (in the order in which
+ they are defined
+ in the config file). The URL is <strong>completely
+ replaced</strong> by the <em>Substitution</em> and the
+ rewriting process continues until all rules have been applied,
+ or it is explicitly terminated by a
+ <code><strong>L</strong></code> flag - see below.</p>
+
+ <p>There is a special substitution string named
+ '<code>-</code>' which means: <strong>NO
+ substitution</strong>! This is useful in providing
+ rewriting rules which <strong>only</strong> match
+ URLs but do not substitute anything for them. It is commonly used
+ in conjunction with the <strong>C</strong> (chain) flag, in order
+ to apply more than one pattern before substitution occurs.</p>
+
+ <p>Additionally you can set special <a name="rewriteflags" id="rewriteflags">flags</a> for <em>Substitution</em> by
+ appending <strong><code>[</code><em>flags</em><code>]</code></strong>
+ as the third argument to the <code>RewriteRule</code>
+ directive. <em>Flags</em> is a comma-separated list of any of the
+ following flags: </p>
+
+ <ul>
+ <li>'<strong><code>chain|C</code></strong>'
+ (<strong>c</strong>hained with next rule)<br />
+ This flag chains the current rule with the next rule
+ (which itself can be chained with the following rule,
+ and so on). This has the following effect: if a rule
+ matches, then processing continues as usual -
+ the flag has no effect. If the rule does
+ <strong>not</strong> match, then all following chained
+ rules are skipped. For instance, it can be used to remove the
+ ``<code>.www</code>'' part, inside a per-directory rule set,
+ when you let an external redirect happen (where the
+ ``<code>.www</code>'' part should not occur!).</li>
+
+ <li>
+ '<strong><code>cookie|CO=</code></strong><em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>]]'
+ (set <strong>co</strong>okie)<br />
+ This sets a cookie in the client's browser. The cookie's name
+ is specified by <em>NAME</em> and the value is
+ <em>VAL</em>. The <em>domain</em> field is the domain of the
+ cookie, such as '.apache.org', the optional <em>lifetime</em>
+ is the lifetime of the cookie in minutes, and the optional
+ <em>path</em> is the path of the cookie</li>
+
+ <li>
+ '<strong><code>env|E=</code></strong><em>VAR</em>:<em>VAL</em>'
+ (set <strong>e</strong>nvironment variable)<br />
+ This forces an environment variable named <em>VAR</em> to
+ be set to the value <em>VAL</em>, where <em>VAL</em> can
+ contain regexp backreferences (<code>$N</code> and
+ <code>%N</code>) which will be expanded. You can use this
+ flag more than once, to set more than one variable. The
+ variables can later be dereferenced in many situations, most commonly
+ from within XSSI (via <code>&lt;!--#echo
+ var="VAR"--&gt;</code>) or CGI (<code>$ENV{'VAR'}</code>).
+ You can also dereference the variable in a later RewriteCond pattern, using
+ <code>%{ENV:VAR}</code>. Use this to strip
+ information from URLs, while maintaining a record of that information.</li>
+
+ <li>'<strong><code>forbidden|F</code></strong>' (force URL
+ to be <strong>f</strong>orbidden)<br />
+ This forces the current URL to be forbidden - it immediately
+ sends back a HTTP response of 403 (FORBIDDEN).
+ Use this flag in conjunction with
+ appropriate RewriteConds to conditionally block some
+ URLs.</li>
+
+ <li>'<strong><code>gone|G</code></strong>' (force URL to be
+ <strong>g</strong>one)<br />
+ This forces the current URL to be gone - it
+ immediately sends back a HTTP response of 410 (GONE). Use
+ this flag to mark pages which no longer exist as gone.</li>
+
+ <li>'<strong><code>last|L</code></strong>'
+ (<strong>l</strong>ast rule)<br />
+ Stop the rewriting process here and don't apply any more
+ rewrite rules. This corresponds to the Perl
+ <code>last</code> command or the <code>break</code> command
+ in C. Use this flag to prevent the currently
+ rewritten URL from being rewritten further by following
+ rules. For example, use it to rewrite the root-path URL
+ ('<code>/</code>') to a real one, <em>e.g.</em>,
+ '<code>/e/www/</code>'.</li>
+
+ <li>'<strong><code>next|N</code></strong>'
+ (<strong>n</strong>ext round)<br />
+ Re-run the rewriting process (starting again with the
+ first rewriting rule). This time, the URL to match is no longer
+ the original URL, but rather the URL returned by the last rewriting rule.
+ This corresponds to the Perl <code>next</code> command or
+ the <code>continue</code> command in C. Use
+ this flag to restart the rewriting process -
+ to immediately go to the top of the loop.<br />
+ <strong>Be careful not to create an infinite
+ loop!</strong></li>
+
+ <li>'<strong><code>nocase|NC</code></strong>'
+ (<strong>n</strong>o <strong>c</strong>ase)<br />
+ This makes the <em>Pattern</em> case-insensitive,
+ ignoring difference between 'A-Z' and
+ 'a-z' when <em>Pattern</em> is matched against the current
+ URL.</li>
+
+ <li>
+ '<strong><code>noescape|NE</code></strong>'
+ (<strong>n</strong>o URI <strong>e</strong>scaping of
+ output)<br />
+ This flag prevents mod_rewrite from applying the usual URI
+ escaping rules to the result of a rewrite. Ordinarily,
+ special characters (such as '%', '$', ';', and so on)
+ will be escaped into their hexcode equivalents ('%25',
+ '%24', and '%3B', respectively); this flag prevents this
+ from happening. This allows percent symbols to appear in
+ the output, as in
+<div class="example"><p><code>
+ RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE]
+</code></p></div>
+
+ which would turn '<code>/foo/zed</code>' into a safe
+ request for '<code>/bar?arg=P1=zed</code>'.
+ </li>
+
+ <li>
+ '<strong><code>nosubreq|NS</code></strong>' (
+ <strong>n</strong>ot for internal
+ <strong>s</strong>ub-requests)<br />
+ This flag forces the rewrite engine to skip a
+ rewrite rule if the current request is an internal
+ sub-request. For instance, sub-requests occur internally
+ in Apache when <code class="module"><a href="../mod/mod_include.html">mod_include</a></code> tries to find out
+ information about possible directory default files
+ (<code>index.xxx</code>). On sub-requests it is not
+ always useful, and can even cause errors, if
+ the complete set of rules are applied. Use this flag to
+ exclude some rules.<br />
+ To decide whether or not to use this rule: if you
+ prefix URLs with CGI-scripts, to force them to be
+ processed by the CGI-script, it's likely that you
+ will run into problems (or significant overhead) on
+ sub-requests. In these cases, use this flag.
+ </li>
+
+ <li>
+ '<strong><code>proxy|P</code></strong>' (force
+ <strong>p</strong>roxy)<br />
+ This flag forces the substitution part to be internally
+ sent as a proxy request and immediately (rewrite
+ processing stops here) put through the <a href="mod_proxy.html">proxy module</a>. You must make
+ sure that the substitution string is a valid URI
+ (typically starting with
+ <code>http://</code><em>hostname</em>) which can be
+ handled by the Apache proxy module. If not, you will get an
+ error from the proxy module. Use this flag to achieve a
+ more powerful implementation of the <a href="mod_proxy.html#proxypass">ProxyPass</a> directive,
+ to map remote content into the namespace of the local
+ server.
+
+ <p>Note: <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> must be enabled in order
+ to use this flag.</p>
+ </li>
+
+ <li>
+ '<strong><code>passthrough|PT</code></strong>'
+ (<strong>p</strong>ass <strong>t</strong>hrough to next
+ handler)<br />
+ This flag forces the rewrite engine to set the
+ <code>uri</code> field of the internal
+ <code>request_rec</code> structure to the value of the
+ <code>filename</code> field. This flag is just a hack to
+ enable post-processing of the output of
+ <code>RewriteRule</code> directives, using
+ <code>Alias</code>, <code>ScriptAlias</code>,
+ <code>Redirect</code>, and other directives from
+ various URI-to-filename translators. For example, to rewrite
+ <code>/abc</code> to <code>/def</code> using
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>, and then
+ <code>/def</code> to <code>/ghi</code> using
+ <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code>:
+<div class="example"><p><code>
+ RewriteRule ^/abc(.*) /def$1 [PT]<br />
+ Alias /def /ghi
+</code></p></div>
+ If you omit the <code>PT</code> flag,
+ <code>mod_rewrite</code> will rewrite
+ <code>uri=/abc/...</code> to
+ <code>filename=/def/...</code> as a full API-compliant
+ URI-to-filename translator should do. Then
+ <code>mod_alias</code> will try to do a
+ URI-to-filename transition, which will fail.
+
+ <p>Note: <strong>You must use this flag if you want to
+ mix directives from different modules which allow
+ URL-to-filename translators</strong>. The typical example
+ is the use of <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> and
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
+ </li>
+
+ <li>'<strong><code>qsappend|QSA</code></strong>'
+ (<strong>q</strong>uery <strong>s</strong>tring
+ <strong>a</strong>ppend)<br />
+ This flag forces the rewrite engine to append a query
+ string part of the substitution string to the existing string,
+ instead of replacing it. Use this when you want to add more
+ data to the query string via a rewrite rule.</li>
+
+ <li>'<strong><code>redirect|R</code>
+ [=<em>code</em>]</strong>' (force <a id="redirect" name="redirect"><strong>r</strong>edirect</a>)<br />
+ Prefix <em>Substitution</em> with
+ <code>http://thishost[:thisport]/</code> (which makes the
+ new URL a URI) to force a external redirection. If no
+ <em>code</em> is given, a HTTP response of 302 (MOVED
+ TEMPORARILY) will be returned. If you want to use other response
+ codes in the range 300-400, simply specify the appropriate number
+ or use one of the following symbolic names:
+ <code>temp</code> (default), <code>permanent</code>,
+ <code>seeother</code>. Use this for rules to
+ canonicalize the URL and return it to the client - to
+ translate ``<code>/~</code>'' into
+ ``<code>/u/</code>'', or to always append a slash to
+ <code>/u/</code><em>user</em>, etc.<br />
+ <strong>Note:</strong> When you use this flag, make
+ sure that the substitution field is a valid URL! Otherwise,
+ you will be redirecting to an invalid location. Remember
+ that this flag on its own will only prepend
+ <code>http://thishost[:thisport]/</code> to the URL, and rewriting
+ will continue. Usually, you will want to stop rewriting at this point,
+ and redirect immediately. To stop rewriting, you should add
+ the 'L' flag.
+ </li>
+
+ <li>'<strong><code>skip|S</code></strong>=<em>num</em>'
+ (<strong>s</strong>kip next rule(s))<br />
+ This flag forces the rewriting engine to skip the next
+ <em>num</em> rules in sequence, if the current rule
+ matches. Use this to make pseudo if-then-else constructs:
+ The last rule of the then-clause becomes
+ <code>skip=N</code>, where N is the number of rules in the
+ else-clause. (This is <strong>not</strong> the same as the
+ 'chain|C' flag!)</li>
+
+ <li>
+ '<strong><code>type|T</code></strong>=<em>MIME-type</em>'
+ (force MIME <strong>t</strong>ype)<br />
+ Force the MIME-type of the target file to be
+ <em>MIME-type</em>. This can be used to
+ set up the content-type based on some conditions.
+ For example, the following snippet allows <code>.php</code> files to
+ be <em>displayed</em> by <code>mod_php</code> if they are called with
+ the <code>.phps</code> extension:
+ <div class="example"><p><code>
+ RewriteRule ^(.+\.php)s$ $1 [T=application/x-httpd-php-source]
+ </code></p></div>
+ </li>
+
+ </ul>
+
+<div class="note"><h3>Home directory expansion</h3>
+<p> When the substitution string begins with a string
+resembling "/~user" (via explicit text or backreferences), mod_rewrite performs
+home directory expansion independent of the presence or configuration
+of <code class="module"><a href="../mod/mod_userdir.html">mod_userdir</a></code>.</p>
+
+<p> This expansion does not occur when the <em>PT</em>
+flag is used on the <code class="directive"><a href="#rewriterule">RewriteRule</a></code>
+directive.</p>
+</div>
+
+<div class="note"><h3>Note: Enabling rewrites in per-directory context</h3>
+ To enable the rewriting engine
+ for per-directory configuration files, you need to set
+ ``<code>RewriteEngine On</code>'' in these files
+ <strong>and</strong> ``<code>Options
+ FollowSymLinks</code>'' must be enabled. If your
+ administrator has disabled override of
+ <code>FollowSymLinks</code> for a user's directory, then
+ you cannot use the rewriting engine. This restriction is
+ needed for security reasons.
+ </div>
+
+ <div class="note"><h3>Note: Pattern matching in per-directory context</h3>
+ Never forget that <em>Pattern</em> is
+applied to a complete URL in per-server configuration
+files. <strong>However, in per-directory configuration files, the
+per-directory prefix (which always is the same for a specific
+directory) is automatically <em>removed</em> for the pattern matching
+and automatically <em>added</em> after the substitution has been
+done.</strong> This feature is essential for many sorts of rewriting -
+without this, you would always have to match the parent
+directory which is not always possible.
+
+ <p>There is one exception: If a substitution string
+ starts with ``<code>http://</code>'', then the directory
+ prefix will <strong>not</strong> be added, and an
+ external redirect or proxy throughput (if flag
+ <strong>P</strong> is used) is forced!</p>
+</div>
+
+
+<div class="note"><h3>Note: Substitution of Absolute URLs</h3>
+ <p>When you prefix a substitution field with
+ <code>http://thishost[:thisport]</code>,
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> will automatically strip that
+ out. This auto-reduction on URLs with an implicit external redirect
+ is most useful in combination with
+ a mapping-function which generates the
+ hostname part.</p>
+
+ <p><strong>Remember:</strong> An unconditional external
+ redirect to your own server will not work with the prefix
+ <code>http://thishost</code> because of this feature. To
+ achieve such a self-redirect, you have to use the
+ <strong>R</strong>-flag.</p>
+</div>
+
+<div class="note"><h3>Note: Query String</h3>
+ <p>The <em>Pattern</em> will not be matched against the query string.
+ Instead, you must use a <code class="directive"><a href="#rewritecond">RewriteCond</a></code> with the
+ <code>%{QUERY_STRING}</code> variable. You can, however, create
+ URLs in the substitution string, containing a query string
+ part. Simply use a question mark inside the substitution string, to
+ indicate that the following text should be re-injected into the
+ query string. When you want to erase an existing query string,
+ end the substitution string with just a question mark. To
+ combine a new query string with an old one, use the
+ <code>[QSA]</code> flag.</p>
+</div>
+
+ <p>Here are all possible substitution combinations and their
+ meanings:</p>
+
+ <p><strong>Inside per-server configuration
+ (<code>httpd.conf</code>)<br />
+ for request ``<code>GET
+ /somepath/pathinfo</code>'':</strong><br />
+ </p>
+
+<div class="note"><pre>
+<strong>Given Rule</strong> <strong>Resulting Substitution</strong>
+---------------------------------------------- ----------------------------------
+^/somepath(.*) otherpath$1 invalid, not supported
+
+^/somepath(.*) otherpath$1 [R] invalid, not supported
+
+^/somepath(.*) otherpath$1 [P] invalid, not supported
+---------------------------------------------- ----------------------------------
+^/somepath(.*) /otherpath$1 /otherpath/pathinfo
+
+^/somepath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo
+ via external redirection
+
+^/somepath(.*) /otherpath$1 [P] doesn't make sense, not supported
+---------------------------------------------- ----------------------------------
+^/somepath(.*) http://thishost/otherpath$1 /otherpath/pathinfo
+
+^/somepath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo
+ via external redirection
+
+^/somepath(.*) http://thishost/otherpath$1 [P] doesn't make sense, not supported
+---------------------------------------------- ----------------------------------
+^/somepath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo
+ via external redirection
+
+^/somepath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo
+ via external redirection
+ (the [R] flag is redundant)
+
+^/somepath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo
+ via internal proxy
+</pre></div>
+
+ <p><strong>Inside per-directory configuration for
+ <code>/somepath</code><br />
+ (<code>/physical/path/to/somepath/.htacccess</code>, with
+ <code>RewriteBase /somepath</code>)<br />
+ for request ``<code>GET
+ /somepath/localpath/pathinfo</code>'':</strong><br />
+ </p>
+
+<div class="note"><pre>
+<strong>Given Rule</strong> <strong>Resulting Substitution</strong>
+---------------------------------------------- ----------------------------------
+^localpath(.*) otherpath$1 /somepath/otherpath/pathinfo
+
+^localpath(.*) otherpath$1 [R] http://thishost/somepath/otherpath/pathinfo
+ via external redirection
+
+^localpath(.*) otherpath$1 [P] doesn't make sense, not supported
+---------------------------------------------- ----------------------------------
+^localpath(.*) /otherpath$1 /otherpath/pathinfo
+
+^localpath(.*) /otherpath$1 [R] http://thishost/otherpath/pathinfo
+ via external redirection
+
+^localpath(.*) /otherpath$1 [P] doesn't make sense, not supported
+---------------------------------------------- ----------------------------------
+^localpath(.*) http://thishost/otherpath$1 /otherpath/pathinfo
+
+^localpath(.*) http://thishost/otherpath$1 [R] http://thishost/otherpath/pathinfo
+ via external redirection
+
+^localpath(.*) http://thishost/otherpath$1 [P] doesn't make sense, not supported
+---------------------------------------------- ----------------------------------
+^localpath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo
+ via external redirection
+
+^localpath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo
+ via external redirection
+ (the [R] flag is redundant)
+
+^localpath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo
+ via internal proxy
+</pre></div>
+
+</div>
+</div>
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