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<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"> en </a> |
<a href="../fr/mod/mod_rewrite.html" hreflang="fr" rel="alternate" title="Français"> fr </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="#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="#vhosts">Rewriting in Virtual Hosts</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="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="vhosts" id="vhosts">Rewriting in Virtual Hosts</a></h2>
<p>By default, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> configuration
settings from the main server context are not inherited by
virtual hosts. To make the main server settings apply to virtual
hosts, you must place the following directives in each <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> section:</p>
<div class="example"><p><code>
RewriteEngine On<br />
RewriteOptions Inherit
</code></p></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/">extended rewrite
documentation.</a></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 -> /abc/def/oldstuff.html (per-server Alias)
/abc/def/oldstuff.html -> /abc/def/newstuff.html (per-dir RewriteRule)
/abc/def/newstuff.html -> /xyz/newstuff.html (per-dir RewriteBase)
/xyz/newstuff.html -> /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/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>$N</code></strong>
(0 <= N <= 9), which provide access to the grouped
parts (in parentheses) of the pattern, from the
<code>RewriteRule</code> which is subject to the current
set of <code>RewriteCond</code> conditions..
</li>
<li>
<strong>RewriteCond backreferences</strong>: These are
backreferences of the form <strong><code>%N</code></strong>
(1 <= N <= 9), which provide access to the grouped
parts (again, in parentheses) of the pattern, from the last matched
<code>RewriteCond</code> in the current set
of conditions.
</li>
<li>
<strong>RewriteMap expansions</strong>: These are
expansions of the form <strong><code>${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 & 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>date and time:</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.</p>
<p>SERVER_NAME and SERVER_PORT depend on the values of
<code class="directive"><a href="../mod/core.html#usecanonicalname">UseCanonicalName</a></code> and
<code class="directive"><a href="../mod/core.html#usecanonicalphysicalport">UseCanonicalPhysicalPort</a></code>
respectively.</p>
<p>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. This value has not been unescaped
(decoded), unlike most other variables below.</dd>
<dt><code>REQUEST_URI</code></dt>
<dd>The path component of the requested URI,
such as "/index.html". This notably excludes the
query string which is available as as its own variable
named <code>QUERY_STRING</code>.</dd>
<dt><code>REQUEST_FILENAME</code></dt>
<dd>The full local filesystem path to the file or
script matching the request, if this has already
been determined by the server at the time
<code>REQUEST_FILENAME</code> is referenced. Otherwise,
such as when used in virtual host context, the same
value as <code>REQUEST_URI</code>.</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><p>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>).</p>
<p>If a substitution occurred and the rewriting continues,
the value of both variables will be updated accordingly.</p>
<p>If used in per-server context (<em>i.e.</em>, before the
request is mapped to the filesystem) SCRIPT_FILENAME and
REQUEST_FILENAME cannot contain the full local filesystem
path since the path is unknown at this stage of processing.
Both variables will initially contain the value of REQUEST_URI
in that case. In order to obtain the full local filesystem
path of the request in per-server context, use an URL-based
look-ahead <code>%{LA-U:REQUEST_FILENAME}</code> to determine
the final value of REQUEST_FILENAME.</p></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>''.
<p>If a HTTP header is used in a condition this header is added to
the Vary header of the response in case the condition evaluates to
to true for the request. It is <strong>not</strong> added if the
condition evaluates to false for the request. Adding the HTTP header
to the Vary header of the response is needed for proper caching.</p>
<p>It has to be kept in mind that conditions follow a short circuit
logic in the case of the '<strong><code>ornext|OR</code></strong>' flag
so that certain conditions might not be evaluated at all.</p></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><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>>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>-x</strong>' (has e<strong>x</strong>ecutable
permissions)<br />
Treats the <em>TestString</em> as a pathname and tests
whether or not it exists, and has executable permissions.
These permissions are determined according to
the underlying OS.</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>
<li>'<strong><code>novary|NV</code></strong>'
(<strong>n</strong>o <strong>v</strong>ary)<br />
If a HTTP header is used in the condition, this flag prevents
this header from being added to the Vary header of the response. <br />
Using this flag might break proper caching of the response if
the representation of this response varies on the value of this header.
So this flag should be only used if the meaning of the Vary header
is well understood.
</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 rewrite configurations are not
inherited by virtual hosts. This means that you need to have a
<code>RewriteEngine on</code> directive for each virtual host
in which you wish to use rewrite rules.</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>
<p>The <code class="directive">RewriteLog</code> log file format is as
follows:</p>
<table>
<tr><th>Description</th><th> Example</th></tr>
<tr>
<td>Remote host IP address</td>
<td>192.168.200.166</td></tr>
<tr><td>Remote login name</td><td>Will usually be "-"</td></tr>
<tr><td>HTTP user auth name</td><td>Username, or "-" if no auth</td></tr>
<tr><td>Date and time of request</td><td>[28/Aug/2009:13:09:09 --0400]</td></tr>
<tr><td>Virtualhost and virtualhost ID</td><td>[www.example.com/sid#84a650]</td></tr>
<tr><td>Request ID, and whether it's a subrequest</td><td>[rid#9f0e58/subreq]</td></tr>
<tr><td>Log entry severity level</td><td>(2)</td></tr>
<tr><td>Text error message</td><td>forcing proxy-throughput with http://127.0.0.1:8080/index.html</td></tr>
</table>
<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. Empty values
behave as if the key was absent, therefore it is not possible
to distinguish between empty-valued keys and absent keys.</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 omitted, the
compile-time default will be chosen.</p>
<p>To create a dbm file from a source text file, use the <a href="../programs/httxt2dbm.html">httxt2dbm</a> utility.</p>
<div class="example"><p><code>
$ httxt2dbm -i mapfile.txt -o mapfile.map
</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.
Module authors can provide additional internal functions by registering
them with the <code>ap_register_rewrite_mapfunc</code> API.
The functions that are provided by default are:
</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 (<STDIN>) {
# ...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#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 no longer available in version 2.1 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> string can currently
only be one of the following:</p>
<dl>
<dt><code>inherit</code></dt>
<dd>
<p>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.</p>
<div class="warning">
Rules inherited from the parent scope are applied
<strong>after</strong> rules specified in the child scope.
</div>
</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> [<em>flags</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">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>. On the first RewriteRule it is applied to the (%-decoded)
<a href="./directive-dict.html#Syntax">URL-path</a> of the request;
subsequent patterns are applied to the output of the last matched
RewriteRule.</p>
<div class="note"><h3>What is matched?</h3>
<p>In <code class="directive"><a href="../mod/core.html#virtualhost">VirtualHost</a></code> context,
The <em>Pattern</em> will initially be matched against the part of the
URL after the hostname and port, and before the query string (e.g. "/app1/index.html").</p>
<p>In <code class="directive"><a href="../mod/core.html#directory">Directory</a></code> and htaccess context,
the <em>Pattern</em> will initially be matched against the
<em>filesystem</em> path, after removing the prefix that lead the server
to the current <code class="directive">RewriteRule</code> (e.g. "app1/index.html"
or "index.html" depending on where the directives are defined).</p>
<p>If you wish to match against the hostname, port, or query string, use a
<code class="directive"><a href="#rewritecond">RewriteCond</a></code> with the
<code>%{HTTP_HOST}</code>, <code>%{SERVER_PORT}</code>, or
<code>%{QUERY_STRING}</code> variables respectively.</p>
</div>
<div class="note"><h3>Per-directory Rewrites</h3>
<ul>
<li>The rewrite engine may be used in <a href="../howto/htaccess.html">.htaccess</a> files and in <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> sections, with some additional
complexity.</li>
<li>To enable the rewrite engine in this context, you need to set
"<code>RewriteEngine On</code>" <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 rewrite engine. This
restriction is required for security reasons.</li>
<li>When using the rewrite engine in <code>.htaccess</code> files the
per-directory prefix (which always is the same for a specific
directory) is automatically <em>removed</em> for the RewriteRule pattern matching
and automatically <em>added</em> after any relative (not starting with a
slash or protocol name) substitution encounters the end of a rule set.
See the <code class="directive"><a href="#rewritebase">RewriteBase</a></code>
directive for more information regarding what prefix will be added back to
relative substitions.</li>
<li> If you wish to match against the full URL-path in a per-directory
(htaccess) RewriteRule, use the <code>%{REQUEST_URI}</code> variable in
a <code class="directive">RewriteCond</code>.</li>
<li>The removed prefix always ends with a slash, meaning the matching occurs against a string which
<em>never</em> has a leading slash. Therefore, a <em>Pattern</em> with <code>^/</code> never
matches in per-directory context.</li>
<li>Although rewrite rules are syntactically permitted in <code class="directive"><a href="../mod/core.html#location"><Location></a></code> and <code class="directive"><a href="../mod/core.html#files"><Files></a></code> sections, this
should never be necessary and is unsupported.</li>
</ul>
</div>
<p>For some hints on <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
expressions</a>, see
the <a href="../rewrite/intro.html#regex">mod_rewrite
Introduction</a>.</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 that replaces the original URL-path that
was matched by <em>Pattern</em>. The <em>Substitution</em> may
be a:</p>
<dl>
<dt>file-system path</dt>
<dd>Designates the location on the file-system of the resource
to be delivered to the client. Substitutions are only
treated as a file-system path when the rule is configured in
server (virtualhost) context and the first component of the
path in the substitution is exists in the file-system</dd>
<dt>URL-path</dt>
<dd>A <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>-relative path to the
resource to be served. Note that <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
tries to guess whether you have specified a file-system path
or a URL-path by checking to see if the first segment of the
path exists at the root of the file-system. For example, if
you specify a <em>Substitution</em> string of
<code>/www/file.html</code>, then this will be treated as a
URL-path <em>unless</em> a directory named <code>www</code>
exists at the root or your file-system, in which case it will
be treated as a file-system path. If you wish other
URL-mapping directives (such as <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code>) to be applied to the
resulting URL-path, use the <code>[PT]</code> flag as
described below.</dd>
<dt>Absolute URL</dt>
<dd>If an absolute URL is specified,
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> checks to see whether the
hostname matches the current host. If it does, the scheme and
hostname are stripped out and the resulting path is treated as
a URL-path. Otherwise, an external redirect is performed for
the given URL. To force an external redirect back to the
current host, see the <code>[R]</code> flag below.</dd>
<dt><code>-</code> (dash)</dt>
<dd>A dash indicates that no substitution should be performed
(the existing path is passed through untouched). This is used
when a flag (see below) needs to be applied without changing
the path.</dd>
</dl>
<p>In addition to plain text, the <em>Substition</em> string 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>Rewrite rules are a applied to the results of previous rewrite
rules, 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
<a href="../rewrite/flags.html#flag_l"><code><strong>L</strong></code> flag</a>,
or other flag which implies immediate termination, such as
<code><strong>END</strong></code> or
<code><strong>F</strong></code>.</p>
<div class="note"><h3>Modifying the Query String</h3>
<p>By default, the query string is passed through unchanged. 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 new and old query strings, use the
<code>[QSA]</code> flag.</p>
</div>
<p>Additionally you can set special <a name="rewriteflags" id="rewriteflags">actions</a> to be performed 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, surround by square
brackets, of any of the flags in the following table. More
details, and examples, for each flag, are available in the <a href="../rewrite/flags.html">Rewrite Flags document</a>.</p>
<table class="bordered">
<tr><th>Flag and syntax</th>
<th>Function</th>
</tr>
<tr>
<td>B</td>
<td>Escape non-alphanumeric characters <em>before</em> applying
the transformation. <em><a href="../rewrite/flags.html#flag_b">details ...</a></em></td>
</tr>
<tr>
<td>chain|C</td>
<td>Rule is chained to the following rule. If the rule fails,
the rule(s) chained to it will be skipped. <em><a href="../rewrite/flags.html#flag_c">details ...</a></em></td>
</tr>
<tr>
<td>cookie|CO=<em>NAME</em>:<em>VAL</em></td>
<td>Sets a cookie in the client browser. Full syntax is:
CO=<em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>[:<em>secure</em>[:<em>httponly</em>]]]] <em><a href="../rewrite/flags.html#flag_co">details ...</a></em>
</td>
</tr>
<tr>
<td>discardpath|DPI</td>
<td>Causes the PATH_INFO portion of the rewritten URI to be
discarded. <em><a href="../rewrite/flags.html#flag_dpi">details
...</a></em></td>
</tr>
<tr>
<td>env|E=[!]<em>VAR</em>[:<em>VAL</em>]</td>
<td>Causes an environment variable <em>VAR</em> to be set (to the
value <em>VAL</em> if provided). The form !<em>VAR</em> causes
the environment variable <em>VAR</em> to be unset.<em><a href="../rewrite/flags.html#flag_e">details ...</a></em></td>
</tr>
<tr>
<td>forbidden|F</td>
<td>Returns a 403 FORBIDDEN response to the client browser.
<em><a href="../rewrite/flags.html#flag_f">details ...</a></em></td>
</tr>
<tr>
<td>gone|G</td>
<td>Returns a 410 GONE response to the client browser. <em><a href="../rewrite/flags.html#flag_g">details ...</a></em></td>
</tr>
<tr>
<td>Handler|H=<em>Content-handler</em></td>
<td>Causes the resulting URI to be sent to the specified
<em>Content-handler</em> for processing. <em><a href="../rewrite/flags.html#flag_h">details ...</a></em></td>
</tr>
<tr>
<td>last|L</td>
<td>Stop the rewriting process immediately and don't apply any
more rules. Especially note caveats for per-directory and
.htaccess context (see also the END flag). <em><a href="../rewrite/flags.html#flag_l">details ...</a></em></td>
</tr>
<tr>
<td>next|N</td>
<td>Re-run the rewriting process, starting again with the first
rule, using the result of the ruleset so far as a starting
point. <em><a href="../rewrite/flags.html#flag_n">details
...</a></em></td>
</tr>
<tr>
<td>nocase|NC</td>
<td>Makes the pattern pattern comparison case-insensitive.
<em><a href="../rewrite/flags.html#flag_nc">details ...</a></em></td>
</tr>
<tr>
<td>noescape|NE</td>
<td>Prevent mod_rewrite from applying hexcode escaping of
special characters in the result of the rewrite. <em><a href="../rewrite/flags.html#flag_ne">details ...</a></em></td>
</tr>
<tr>
<td>nosubreq|NS</td>
<td>Causes a rule to be skipped if the current request is an
internal sub-request. <em><a href="../rewrite/flags.html#flag_ns">details ...</a></em></td>
</tr>
<tr>
<td>proxy|P</td>
<td>Force the substitution URL to be internally sent as a proxy
request. <em><a href="../rewrite/flags.html#flag_p">details
...</a></em></td>
</tr>
<tr>
<td>passthrough|PT</td>
<td>Forces the resulting URI to be passed back to the URL
mapping engine for processing of other URI-to-filename
translators, such as <code>Alias</code> or
<code>Redirect</code>. <em><a href="../rewrite/flags.html#flag_pt">details ...</a></em></td>
</tr>
<tr>
<td>qsappend|QSA</td>
<td>Appends any query string created in the rewrite target to
any query string that was in the original request URL. <em><a href="../rewrite/flags.html#flag_qsa">details ...</a></em></td>
</tr>
<tr>
<td>redirect|R[=<em>code</em>]</td>
<td>Forces an external redirect, optionally with the specified
HTTP status code. <em><a href="../rewrite/flags.html#flag_r">details ...</a></em>
</td>
</tr>
<tr>
<td>skip|S=<em>num</em></td>
<td>Tells the rewriting engine to skip the next <em>num</em>
rules if the current rule matches. <em><a href="../rewrite/flags.html#flag_s">details ...</a></em></td>
</tr>
<tr>
<td>type|T=<em>MIME-type</em></td>
<td>Force the <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME-type</a> of the target file
to be the specified type. <em><a href="../rewrite/flags.html#flag_t">details ...</a></em></td>
</tr>
</table>
<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>
<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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