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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">&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="#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 slash ('\')
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">&lt;VirtualHost&gt;</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/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>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. 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>''.
<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>&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>-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>
<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 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.
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>
<li>
<p><strong>SQL Query</strong><br />
MapType: <code>dbd</code> or <code>fastdbd</code>,
MapSource: An SQL SELECT statement that takes a single
argument and returns a single value.</p>
<p>This uses <code class="module"><a href="../mod/mod_dbd.html">mod_dbd</a></code> to implement a rewritemap
by lookup in an SQL database. There are two forms:
<code>fastdbd</code> caches database lookups internally,
<code>dbd</code> doesn't. So <code>dbd</code> incurs a
performance penalty but responds immediately if the database
contents are updated, while <code>fastdbd</code> is more
efficient but won't re-read database contents until server
restart.</p>
<p>If a query returns more than one row, a random row from
the result set is used.</p>
<div class="example"><h3>Example</h3><p><code>
RewriteMap myquery "fastdbd:SELECT destination FROM rewrite WHERE source = %s"
</code></p></div>
</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>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>
</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
<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>The <em>Pattern</em> will initially be matched against the part of the
URL after the hostname and port, and before the query string. 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>
<p>For some hints on <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
expressions</a>, see
the <a href="../rewrite/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.</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>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.</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 following flags: </p>
<dl>
<dt>'<code>B</code>' (escape backreferences)</dt>
<dd><p>Apache has to unescape URLs before mapping them,
so backreferences will be unescaped at the time they are applied.
Using the B flag, non-alphanumeric characters in backreferences
will be escaped. For example, consider the rule:</p>
<pre><code> RewriteRule ^(.*)$ index.php?show=$1 </code></pre>
<p>This will map <code>/C++</code> to <code>index.php?show=/C++</code>.
But it will also map <code>/C%2b%2b</code> to
<code>index.php?show=/C++</code>, because the <code>%2b</code>
has been unescaped. With the B flag, it will instead map to
<code>index.php?show=/C%2b%2b</code>.</p>
<p>This escaping is particularly necessary in a proxy situation,
when the backend may break if presented with an unescaped URL.</p>
</dd>
<dt>'<code>chain|C</code>'
(chained with next rule)</dt><dd>
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!).</dd>
<dt>'<code>cookie|CO=</code><em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>[:<em>secure</em>[:<em>httponly</em>]]]]'
(set cookie)</dt><dd>
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 (0 means expires at end
of session), and the optional
<em>path</em> is the path of the cookie. If <em>secure</em>
is set to 'secure', 'true' or '1', the cookie is only transmitted via secured
connections. If <em>httponly</em> is set to 'HttpOnly', 'true' or '1', the
<code>HttpOnly</code> flag is used, making the cookie inaccessible
to JavaScript code on browsers that support this feature.</dd>
<dt>
'<code>env|E=</code><em>VAR</em>:<em>VAL</em>'
(set environment variable)</dt><dd>
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.</dd>
<dt>'<code>forbidden|F</code>' (force URL
to be forbidden)</dt><dd>
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.</dd>
<dt>'<code>gone|G</code>' (force URL to be
gone)</dt><dd>
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.</dd>
<dt>
'<code>handler|H</code>=<em>Content-handler</em>'
(force Content handler)</dt><dd>
Force the Content-handler of the target file to be
<em>Content-handler</em>. For instance, this can be used to
simulate the <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> directive
<code class="directive"><a href="../mod/mod_alias.html#scriptalias">ScriptAlias</a></code>,
which internally forces all files
inside the mapped directory to have a handler of
``<code>cgi-script</code>''.</dd>
<dt>'<code>last|L</code>'
(last rule)</dt><dd> 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. Remember, however, that if the
<code class="directive">RewriteRule</code> generates an internal
redirect (which frequently occurs when rewriting in a
per-directory context), this will reinject the request and
will cause processing to be repeated starting from the first
<code class="directive">RewriteRule</code>.</dd>
<dt>'<code>next|N</code>'
(next round)</dt><dd>
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.
<strong>Be careful not to create an infinite
loop!</strong></dd>
<dt>'<code>nocase|NC</code>'
(no case)</dt><dd>
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.</dd>
<dt>
'<code>noescape|NE</code>'
(no URI escaping of
output)</dt><dd>
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>'.
</dd>
<dt>
'<code>nosubreq|NS</code>'
(not for internal
sub-requests)</dt><dd>
<p>This flag forces the rewriting engine to skip a
rewriting 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> files). 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.</p>
<p>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.</p>
</dd>
<dt>
'<code>proxy|P</code>' (force
proxy)</dt><dd>
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>
</dd>
<dt>
'<code>passthrough|PT</code>'
(pass through to next
handler)</dt><dd>
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>
<p>The <code>PT</code> flag implies the <code>L</code> flag:
rewriting will be stopped in order to pass the request to
the next phase of processing.</p>
</dd>
<dt>'<code>qsappend|QSA</code>'
(query string
append)</dt><dd>
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.</dd>
<dt>'<code>redirect|R</code>
[=<em>code</em>]' (force <a id="redirect" name="redirect">redirect</a>)</dt><dd>
<p>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, 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.</p>
<p>While this is typically used for redirects, any valid status
code can be given here. If the status code is outside the redirect
range (300-399), then the <em>Substitution</em> string is dropped
and rewriting is stopped as if the <code>L</code> flag was
used.</p>
</dd>
<dt>'<code>skip|S</code>=<em>num</em>'
(skip next rule(s))</dt><dd>
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!)</dd>
<dt>
'<code>type|T</code>=<em>MIME-type</em>'
(force MIME type)</dt><dd>
Force the <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME-type</a> 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>
</dd>
</dl>
<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>Per-directory Rewrites</h3>
<p>The rewrite engine may be used in <a href="../howto/htaccess.html">.htaccess</a> files. To enable the
rewrite engine for these files 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.</p>
<p>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 pattern matching
and automatically <em>added</em> after the substitution has been
done. 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. 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 using flag <strong>P</strong>) is forced. See the
<code class="directive"><a href="#rewritebase">RewriteBase</a></code> directive for
more information.</p>
<p>The rewrite engine may also be used in <code class="directive"><a href="../mod/core.html#directory">&lt;Directory&gt;</a></code> sections with the same
prefix-matching rules as would be applied to <code>.htaccess</code>
files. It is usually simpler, however, to avoid the prefix substitution
complication by putting the rewrite rules in the main server or
virtual host context, rather than in a <code class="directive"><a href="../mod/core.html#directory">&lt;Directory&gt;</a></code> section.</p>
<p>Although rewrite rules are syntactically permitted in <code class="directive"><a href="../mod/core.html#location">&lt;Location&gt;</a></code> sections, this
should never be necessary and is unsupported.</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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