<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
+ 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,
- for instance server variables, environment variables, HTTP
- headers, time stamps and even external database lookups in
- various formats can be used to achieve a really granular URL
+ 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 even generate query-string
+ (<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>
System-view. </p>
<p>Notice: These variables hold the URI/URL <em>as they were
- initially requested</em>, <em>i.e.</em>, <em>before</em> any
- rewriting. This is important because the rewriting process is
+ 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>
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>). There it will act locally,
- <em>i.e.</em>, the local directory prefix is stripped at this
- stage of processing and your rewriting rules act only on the
- remainder. At the end it is automatically added back to the
+ (<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>But at most websites URLs are NOT
+ filepath itself. <strong>However, for most websites, URLs are NOT
directly related to physical filename paths, so this
- assumption will usually be wrong!</strong> There you have to
+ 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 have to use
+related to physical file paths, you will need to use
<code class="directive">RewriteBase</code> in every <code>.htaccess</code>
-file
s where you want to use <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directives.
+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>
Result:
/abc/def/newstuff.html
</pre>
- <p>This seems very complicated but is
- the correct Apache internal processing, because the
- per-directory rewriting comes too late in the
- process. So, when it occurs the (rewritten) request
- has to be re-injected into the Apache kernel! BUT:
- While this seems like a serious overhead, it really
- isn't, because this re-injection happens fully
- internally to the Apache server and the same
- procedure is used by many other operations inside
- Apache. So, you can be sure the design and
- implementation is correct.</p>
+ <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.
+ 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>
<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. Precede a <code class="directive"><a href="#rewriterule">RewriteRule</a></code> directive with one
- or more <code class="directive">RewriteCond</code> directives. The following
- rewriting rule is only used if its pattern matches the current
- state of the URI <strong>and</strong> if these additional
- conditions apply too.</p>
+ 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 contains the
+ <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
-
- <p class="indent">
- <strong><code>$N</code></strong>
- </p>
- (0 <= N <= 9) which provide access to the grouped
- parts (parenthesis!) of the pattern from the
- corresponding <code>RewriteRule</code> directive (the one
- following the current bunch of <code>RewriteCond</code>
- directives).
+ backreferences of the form <strong><code>$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
-
- <p class="indent">
- <strong><code>%N</code></strong>
- </p>
- (1 <= N <= 9) which provide access to the grouped
- parts (parentheses!) of the pattern from the last matched
- <code>RewriteCond</code> directive in the current bunch
+ 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
-
- <p class="indent">
- <strong><code>${mapname:key|default}</code></strong>
- </p>
+ expansions of the form <strong><code>${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
-
- <p class="indent">
<strong><code>%{</code> <em>NAME_OF_VARIABLE</em>
<code>}</code></strong>
- </p>
where <em>NAME_OF_VARIABLE</em> can be a string taken
from the following list:
</tr>
</table>
-<div class="note">
<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:</p>
-
+ mod_rewrite include those below.</p>
+ <div class="note">
<dl>
<dt><code>IS_SUBREQ</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
+ 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>
</li>
</ul>
- <p>Special Notes:</p>
+ <p>Other things you should be aware of:</p>
<ol>
<li>The variables SCRIPT_FILENAME and REQUEST_FILENAME
- contain the same value, <em>i.e.</em>, the value of the
+ 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 just the commonly known CGI variable name
- while the second is the consistent counterpart to
+ 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>There is the special format:
- <code>%{ENV:variable}</code> where <em>variable</em> can be
- any environment variable. This is looked-up via internal
+ <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>There is the special format:
- <code>%{SSL:variable}</code> where <em>variable</em> is the
+ <li>
+ <code>%{SSL:variable}</code>, where <em>variable</em> is the
name of an <a href="mod_ssl.html#envvars">SSL environment
- variable</a>; this can be used whether or not
+ 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>There is the special format:
- <code>%{HTTP:header}</code> where <em>header</em> can be
- any HTTP MIME-header name. This is looked-up from the HTTP
- request. Example: <code>%{HTTP:Proxy-Connection}</code> is
+ <li>
+ <code>%{HTTP:header}</code>, where <em>header</em> can be
+ any HTTP MIME-header name, can always be used to obtain the
+ value of a header sent in the HTTP request.
+ Example: <code>%{HTTP:Proxy-Connection}</code> is
the value of the HTTP header
``<code>Proxy-Connection:</code>''.</li>
- <li>There is the special format
- <code>%{LA-U:variable}</code> for look-aheads which perform
+ <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>. Use this when you want to use a
- variable for rewriting which is actually set later in an
- API phase and thus is not available at the current stage.
- For instance when you want to rewrite according to the
+ 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 have
- to use <code>%{LA-U:REMOTE_USER}</code> because this
- variable is set by the authorization phases which come
- <em>after</em> the URL translation phase where mod_rewrite
- operates. On the other hand, because mod_rewrite implements
+ 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> there.</li>
+ <code>%{REMOTE_USER}</code> in that context.</p></li>
- <li>There is the special format:
- <code>%{LA-F:variable}</code> which performs an internal
- (filename-based) sub-request to determine the final value
- of <em>variable</em>. Most of the time this is the same as
+ <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,
- <em>i.e.</em>, a regular expression which is applied to the
- current instance of the <em>TestString</em>, <em>i.e.</em>,
- <em>TestString</em> is evaluated and then matched against
+ 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
use one of the following:
<ul>
- <li>'<strong><CondPattern</strong>' (is lexically
- lower)<br />
- Treats the <em>CondPattern</em> as a plain string and
- compares it lexically to <em>TestString</em>. True if
- <em>TestString</em> is lexically lower than
+ <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>' (is lexically
- greater)<br />
- Treats the <em>CondPattern</em> as a plain string and
- compares it lexically to <em>TestString</em>. True if
- <em>TestString</em> is lexically greater than
+ <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>' (is lexically
+ <li>'<strong>=CondPattern</strong>' (lexicographically
equal)<br />
- Treats the <em>CondPattern</em> as a plain string and
- compares it lexically to <em>TestString</em>. True if
- <em>TestString</em> is lexically equal to
- <em>CondPattern</em>, i.e the two strings are exactly
- equal (character by character). If <em>CondPattern</em>
- is just <code>""</code> (two quotation marks) this
+ 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
- if it exists and is a directory.</li>
+ 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
- if it exists and is a regular file.</li>
+ whether or not it exists, and is a regular file.</li>
- <li>'<strong>-s</strong>' (is regular file with
+ <li>'<strong>-s</strong>' (is regular file, with
<strong>s</strong>ize)<br />
- Treats the <em>TestString</em> as a pathname and tests
- if it exists and is a regular file with size greater
+ 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
- if it exists and is a symbolic link.</li>
+ 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
- if it exists and has execution permissions. These permissions
- are determined depending on the underlying OS.</li>
+ 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
+ <li>'<strong>-F</strong>' (is existing file, via
subrequest)<br />
- Checks if <em>TestString</em> is a valid file and
+ 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 determine the check, so use it with care
- because it decreases your servers performance!</li>
+ 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
+ <li>'<strong>-U</strong>' (is existing URL, via
subrequest)<br />
- Checks if <em>TestString</em> is a valid URL and
+ 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 determine the check, so use it with care
- because it decreases your server's performance!</li>
+ subrequest to do the check, so use it with care -
+ it can impact your server's performance!</li>
</ul>
-<div class="note"><h3>Notice</h3>
+<div class="note"><h3>Note:</h3>
All of these tests can
also be prefixed by an exclamation mark ('!') to
negate their meaning.
</div>
</li>
- </ol>
-
- <p>Additionally you can set special flags for
- <em>CondPattern</em> by appending</p>
- <p class="indent">
+ <li>You can also set special flags for
+ <em>CondPattern</em> by appending
<strong><code>[</code><em>flags</em><code>]</code></strong>
- </p>
-
- <p>as the third argument to the <code>RewriteCond</code>
- directive. <em>Flags</em> is a comma-separated list of the
- following flags:</p>
+ 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:</li>
<ul>
<li>'<strong><code>nocase|NC</code></strong>'
(<strong>n</strong>o <strong>c</strong>ase)<br />
- This makes the test case-insensitive, <em>i.e.</em>, there
- is no difference between 'A-Z' and 'a-z' both in the
+ 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
<li>
'<strong><code>ornext|OR</code></strong>'
(<strong>or</strong> next condition)<br />
- Use this to combine rule conditions with a local OR
+ Use this to combine rule conditions with a local OR
instead of the implicit AND. Typical example:
<div class="example"><pre>
RewriteRule ...some special stuff for any of these hosts...
</pre></div>
- Without this flag you would have to write the cond/rule
- three times.
+ Without this flag you would have to write the condition/rule
+ pair three times.
</li>
</ul>
+ </ol>
<p><strong>Example:</strong></p>
RewriteRule ^/$ /homepage.std.html [L]
</pre></div>
- <p>Interpretation: If you use Netscape Navigator as your
- browser (which identifies itself as 'Mozilla'), then you
- get the max homepage, which includes Frames, <em>etc.</em>
- If you use the Lynx browser (which is Terminal-based), then
- you get the min homepage, which contains no images, no
- tables, <em>etc.</em> If you use any other browser you get
- the standard homepage.</p>
+ <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="note"><h3>Security</h3>
See the <a href="../misc/security_tips.html">Apache Security Tips</a>
-document for details on why your security could be compromised if the
+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>
<code>}</code></strong>
</p>
- <p>When such a construct occurs the map <em>MapName</em> is
+ <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
MapType: <code>int</code>, MapSource: Internal Apache
function
- <p>Here the source is an internal Apache function.
+ <p>Here, the source is an internal Apache function.
Currently you cannot create your own, but the following
- functions already exists:</p>
+ functions already exist:</p>
<ul>
<li><strong>toupper</strong>:<br />
- Converts the looked up key to all upper case.</li>
+ Converts the key to all upper case.</li>
<li><strong>tolower</strong>:<br />
- Converts the looked up key to all lower case.</li>
+ Converts the key to all lower case.</li>
<li><strong>escape</strong>:<br />
- Translates special characters in the looked up key to
+ Translates special characters in the key to
hex-encodings.</li>
<li><strong>unescape</strong>:<br />
- Translates hex-encodings in the looked up key back to
+ Translates hex-encodings in the key back to
special characters.</li>
</ul>
</li>
path to valid regular file
<p>Here the source is a program, not a map file. To
- create it you can use the language of your choice, but
- the result has to be a executable (<em>i.e.</em>, either
+ 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 at startup of the Apache
- servers and then communicates with the rewriting engine
- over its <code>stdin</code> and <code>stdout</code>
+ <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
<p>But be very careful:</p>
<ol>
- <li>``<em>Keep it simple, stupid</em>'' (KISS), because
- if this program hangs it will hang the Apache server
- when the rule occurs.</li>
+ <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>Avoid one common mistake: never do buffered I/O on
- <code>stdout</code>! This will cause a deadloop! Hence
- the ``<code>$|=1</code>'' in the above example...</li>
+ <li>A common mistake is to use buffered I/O on
+ <code>stdout</code>. Avoid this, as it will cause a deadloop!
+ ``<code>$|=1</code>'' is used above, to prevent this.</li>
- <li>Use the <code class="directive"><a href="#rewritelock">RewriteLock</a></code> directive to
- define a lockfile mod_rewrite can use to synchronize the
- communication to the program. By default no such
+ <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>
<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 be currently only one:</p>
+ 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
+ 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
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The cookie-flag is available in Apache 2.0.40 and later.</td></tr>
</table>
<p>The <code class="directive">RewriteRule</code> directive is the real
- rewriting workhorse. The directive can occur more than once.
- Each directive then defines one single rewriting rule. The
- <strong>definition order</strong> of these rules is
- <strong>important</strong>, because this order is used when
- applying the rules at run-time.</p>
+ rewriting workhorse. The directive can occur more than once,
+ with each instance defining a single rewrite rule. The
+ order in which these rules are defined is important - this is the order
+ in which they will be applied at run-time.</p>
<p><a id="patterns" name="patterns"><em>Pattern</em></a> is
a perl compatible <a id="regexp" name="regexp">regular
- expression</a> which gets applied to the current URL. Here
- ``current'' means the value of the URL when this rule gets
+ expression</a>, which is applied to the current URL.
+ ``Current'' means the value of the URL when this rule is
applied. This may not be the originally requested URL,
- because any number of rules may already have matched and made
- alterations to it.</p>
+ which may already have matched a previous rule, and have been
+ altered.</p>
- <p>Some hints
about the syntax of <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
+ <p>Some hints
on the syntax of <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular
expressions</a>:</p>
<div class="note"><pre>
<strong>Text:</strong>
<strong><code>.</code></strong> Any single character
- <strong><code>[</code></strong>chars<strong><code>]</code></strong> Character class: One of chars
- <strong><code>[^</code></strong>chars<strong><code>]</code></strong> Character class: None of chars
+ <strong><code>[</code></strong>chars<strong><code>]</code></strong> Character class: Any character of the class ``chars''
+ <strong><code>[^</code></strong>chars<strong><code>]</code></strong> Character class: Not a character of the class ``chars''
text1<strong><code>|</code></strong>text2 Alternative: text1 or text2
<strong>Quantifiers:</strong>
- <strong><code>?</code></strong> 0 or 1 of the preceding text
- <strong><code>*</code></strong> 0 or N of the preceding text (N > 0)
- <strong><code>+</code></strong> 1 or N of the preceding text (N > 1)
+ <strong><code>?</code></strong> 0 or 1 occurrences of the preceding text
+ <strong><code>*</code></strong> 0 or N occurrences of the preceding text (N > 0)
+ <strong><code>+</code></strong> 1 or N occurrences of the preceding text (N > 1)
<strong>Grouping:</strong>
<strong><code>(</code></strong>text<strong><code>)</code></strong> Grouping of text
- (either to set the borders of an alternative or
- for making backreferences where the <strong>N</strong>th group can
- be used on the RHS of a RewriteRule with <code>$</code><strong>N</strong>)
+ (used either to set the borders of an alternative as above, or
+ to make backreferences, where the <strong>N</strong>th group can
+ be referred to on the RHS of a RewriteRule as <code>$</code><strong>N</strong>)
<strong>Anchors:</strong>
- <strong><code>^</code></strong> Start of line anchor
- <strong><code>$</code></strong> End of line anchor
+ <strong><code>^</code></strong> Start-of-line anchor
+ <strong><code>$</code></strong> End-of-line anchor
<strong>Escaping:</strong>
- <strong><code>\</code></strong>char escape that particular char
- (for instance to specify the chars "<code>.[]()</code>" <em>etc.</em>)
+ <strong><code>\</code></strong>char escape the given char
+ (for instance, to specify the chars "<code>.[]()</code>" <em>etc.</em>)
</pre></div>
- <p>For more information about regular expressions have a look at the
+ <p>For more information about regular expressions, have a look at the
perl regular expression manpage ("<a href="http://www.perldoc.com/perl5.6.1/pod/perlre.html">perldoc
perlre</a>"). If you are interested in more detailed
information about regular expressions and their variants
- (POSIX regex <em>etc.</em>) have a look at the
- following dedicated book on this topic:</p>
+ (POSIX regex etc.) the following book is dedicated to this topic:</p>
<p class="indent">
<em>Mastering Regular Expressions, 2nd Edition</em><br />
ISBN 0-596-00289-0<br />
</p>
- <p>Additionally in mod_rewrite the NOT character
- ('<code>!</code>') is a possible pattern prefix. This gives
- you the ability to negate a pattern; to say, for instance:
+ <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>Notice</h3>
-When using the NOT character
- to negate a pattern you cannot have grouped wildcard
- parts in the pattern. This is impossible because when the
- pattern does NOT match, there are no contents for the
- groups. In consequence, if negated patterns are used, you
- cannot use <code>$N</code> in the substitution
- string!
+<div class="note"><h3>Note</h3>
+When using the NOT character to negate a pattern, you cannot include
+grouped wildcard parts in that pattern. This is because, when the
+pattern does NOT match (ie, the negation matches), there are no
+contents for the groups. Thus, if negated patterns are used, you
+cannot use <code>$N</code> in the substitution string!
</div>
- <p><a id="rhs" name="rhs"><em>Substitution</em></a> of a
- rewriting rule is the string which is substituted for (or
- replaces) the original URL for which <em>Pattern</em>
- matched. Beside plain text you can use</p>
+ <p>The <a id="rhs" name="rhs"><em>substitution</em></a> of a
+ rewrite rule is the string which is substituted for (or
+ replaces) the original URL which <em>Pattern</em>
+ matched. In addition to plain text, it can include</p>
<ol>
- <li>back-references <code>$N</code> to the RewriteRule
+ <li>back-references (<code>$N</code>) to the RewriteRule
pattern</li>
- <li>back-references <code>%N</code> to the last matched
+ <li>back-references (<code>%N</code>) to the last matched
RewriteCond pattern</li>
<li>server-variables as in rule condition test-strings
<li><a href="#mapfunc">mapping-function</a> calls
(<code>${mapname:key|default}</code>)</li>
</ol>
- <p>Back-references are <code>$</code><strong>N</strong>
- (<strong>N</strong>=0..9) identifiers which will be replaced
+ <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 of
- the above list. </p>
+ These three types of variables are expanded in the order above.</p>
- <p>As already mentioned above, all the rewriting rules are
- applied to the <em>Substitution</em> (in the order of
- definition in the config file). The URL is <strong>completely
+ <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 goes on until there are no more rules
- unless explicitly terminated by a
- <code><strong>L</strong></code> flag - see below.</p>
+ rewriting process continues until all rules have been applied,
+ or it is explicitly terminated by a
+ <code><strong>L</strong></code> flag.</p>
<p>There is a special substitution string named
'<code>-</code>' which means: <strong>NO
- substitution</strong>! Sounds silly? No, it is useful to
- provide rewriting rules which <strong>only</strong> match
- some URLs but do no substitution, <em>e.g.</em>, in
- conjunction with the <strong>C</strong> (chain) flag to be
- able to have more than one pattern to be applied before a
- substitution occurs.</p>
-
-<div class="note"><h3>Query String</h3>
- <p>The <em>Pattern</em> will not match against the query string.
- Instead, you must use a <code class="directive"><a href="#rewritecond">RewriteCond</a></code> with the
- <code>%{QUERY_STRING}</code> variable. You can, however, create
- URLs in the substitution string containing a query string
- part. Just use a question mark inside the substitution string to
- indicate that the following stuff should be re-injected into the
- query string. When you want to erase an existing query string,
- end the substitution string with just the question mark. To
- combine a new query string with an old one, use the
- <code>[QSA]</code> flag (see below).</p>
-</div>
+ substitution</strong>! This is useful in providing
+ rewriting rules which <strong>only</strong> match
+ URLs but do not substitute anything for them. It is commonly used
+ in conjunction with the <strong>C</strong> (chain) flag, in order
+ to apply more than one pattern before substitution occurs.</p>
-<div class="note"><h3>Substitution of Absolute URLs</h3>
- <p>There is a special feature:
- When you prefix a substitution field with
- <code>http://</code><em>thishost</em>[<em>:thisport</em>]
- then <strong>mod_rewrite</strong> automatically strips it
- out. This auto-reduction on implicit external redirect
- URLs is a useful and important feature when used in
- combination with a mapping-function which generates the
- hostname part. Have a look at the first example in the
- example section below to understand this.</p>
-
- <p><strong>Remember:</strong> An unconditional external
- redirect to your own server will not work with the prefix
- <code>http://thishost</code> because of this feature. To
- achieve such a self-redirect, you have to use the
- <strong>R</strong>-flag (see below).</p>
-</div>
<p>Additionally you can set special <a name="rewriteflags" id="rewriteflags">flags</a> for <em>Substitution</em> by
- appending</p>
-
- <p class="indent">
- <strong><code>[</code><em>flags</em><code>]</code></strong>
- </p>
- <p>
+ appending <strong><code>[</code><em>flags</em><code>]</code></strong>
as the third argument to the <code>RewriteRule</code>
- directive. <em>Flags</em> is a comma-separated list of the
+ directive. <em>Flags</em> is a comma-separated list of any of the
following flags: </p>
<ul>
(<strong>c</strong>hained with next rule)<br />
This flag chains the current rule with the next rule
(which itself can be chained with the following rule,
- <em>etc.</em>). This has the following effect: if a rule
- matches, then processing continues as usual, <em>i.e.</em>,
+ 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, use it to remove the
- ``<code>.www</code>'' part inside a per-directory rule set
+ 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 to occur!).</li>
+ ``<code>.www</code>'' part should not occur!).</li>
<li>
'<strong><code>cookie|CO=</code></strong><em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>]]'
(set <strong>co</strong>okie)<br />
- This sets a cookie on the client's browser. The cookie's name
+ 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>
+ cookie, such as '.apache.org', the optional <em>lifetime</em>
is the lifetime of the cookie in minutes, and the optional
<em>path</em> is the path of the cookie</li>
<li>
'<strong><code>env|E=</code></strong><em>VAR</em>:<em>VAL</em>'
(set <strong>e</strong>nvironment variable)<br />
- This forces an environment variable named <em>VAR</em> to
+ 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 be later dereferenced in many situations, but
- usually from within XSSI (via <code><!--#echo
- var="VAR"--></code>) or CGI (<em>e.g.</em>
- <code>$ENV{'VAR'}</code>). Additionally you can dereference
- it in a following RewriteCond pattern via
- <code>%{ENV:VAR}</code>. Use this to strip but remember
- information from URLs.</li>
+ contain regexp backreferences (<code>$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><!--#echo
+ var="VAR"--></code>) or CGI (<code>$ENV{'VAR'}</code>).
+ You can also dereference the variable in a later RewriteCond pattern, using
+ <code>%{ENV:VAR}</code>. Use this to strip
+ information from URLs, while maintaining a record of that information.</li>
<li>'<strong><code>forbidden|F</code></strong>' (force URL
to be <strong>f</strong>orbidden)<br />
- This forces the current URL to be forbidden,
- <em>i.e.</em>, it immediately sends back a HTTP response of
- 403 (FORBIDDEN). Use this flag in conjunction with
+ This forces the current URL to be forbidden - it immediately
+ sends back a HTTP response of 403 (FORBIDDEN).
+ Use this flag in conjunction with
appropriate RewriteConds to conditionally block some
URLs.</li>
<li>'<strong><code>gone|G</code></strong>' (force URL to be
<strong>g</strong>one)<br />
- This forces the current URL to be gone, <em>i.e.</em>, it
+ This forces the current URL to be gone - it
immediately sends back a HTTP response of 410 (GONE). Use
this flag to mark pages which no longer exist as gone.</li>
(force Content <strong>h</strong>andler)<br />
Force the Content-handler of the target file to be
<em>Content-handler</em>. For instance, this can be used to
- simulate the <code>mod_alias</code> directive
- <code>ScriptAlias</code> which internally forces all files
+ 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>''.</li>
<li>'<strong><code>last|L</code></strong>'
(<strong>l</strong>ast rule)<br />
- Stop the rewriting process here and don't apply any more
- rewriting rules. This corresponds to the Perl
+ 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
- from the C language. Use this flag to prevent the currently
+ in C. Use this flag to prevent the currently
rewritten URL from being rewritten further by following
rules. For example, use it to rewrite the root-path URL
('<code>/</code>') to a real one, <em>e.g.</em>,
<li>'<strong><code>next|N</code></strong>'
(<strong>n</strong>ext round)<br />
- Re-run the rewriting process (starting again with the
- first rewriting rule). Here the URL to match is again not
- the original URL but the URL from the last rewriting rule.
+ 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 from the C language. Use
- this flag to restart the rewriting process, <em>i.e.</em>,
+ the <code>continue</code> command in C. Use
+ this flag to restart the rewriting process -
to immediately go to the top of the loop.<br />
- <strong>But be careful not to create an infinite
+ <strong>Be careful not to create an infinite
loop!</strong></li>
<li>'<strong><code>nocase|NC</code></strong>'
(<strong>n</strong>o <strong>c</strong>ase)<br />
- This makes the <em>Pattern</em> case-insensitive,
- <em>i.e.</em>, there is no difference between 'A-Z' and
+ This makes the <em>Pattern</em> case-insensitive,
+ ignoring difference between 'A-Z' and
'a-z' when <em>Pattern</em> is matched against the current
URL.</li>
'<strong><code>noescape|NE</code></strong>'
(<strong>n</strong>o URI <strong>e</strong>scaping of
output)<br />
- This flag keeps mod_rewrite from applying the usual URI
+ 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 being done. This allows percent symbols to appear in
+ from happening. This allows percent symbols to appear in
the output, as in
<div class="example"><p><code>
RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE]
</code></p></div>
-
which would turn '<code>/foo/zed</code>' into a safe
request for '<code>/bar?arg=P1=zed</code>'.
</li>
<li>
- '<strong><code>nosubreq|NS</code></strong>' (used only if
- <strong>n</strong>o internal
- <strong>s</strong>ub-request)<br />
- This flag forces the rewriting engine to skip a
+ '<strong><code>nosubreq|NS</code></strong>'
+ (<strong>n</strong>ot for internal
+ <strong>s</strong>ub-requests)<br />
+ 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>mod_include</code> tries to find out
+ in Apache when <code class="module"><a href="../mod/mod_include.html">mod_include</a></code> tries to find out
information about possible directory default files
- (<code>index.xxx</code>). On sub-requests it is not
- always useful and even sometimes causes a failure to if
+ (<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.<br />
-
-
- <p>Use the following rule for your decision: whenever you
- prefix some URLs with CGI-scripts to force them to be
- processed by the CGI-script, the chance is high that you
- will run into problems (or even overhead) on
- sub-requests. In these cases, use this flag.</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.
</li>
<li>
'<strong><code>proxy|P</code></strong>' (force
<strong>p</strong>roxy)<br />
- This flag forces the substitution part to be internally
- forced as a proxy request and immediately (<em>i.e.</em>,
- rewriting rule processing stops here) put through the <a href="mod_proxy.html">proxy module</a>. You have to make
+ 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
- (<em>e.g.</em>, typically starting with
+ (typically starting with
<code>http://</code><em>hostname</em>) which can be
- handled by the Apache proxy module. If not you get an
+ 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 some remote stuff into the namespace of the local
+ to map remote content into the namespace of the local
server.
- <p>Not
ice: <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> must be enabled in order
+ <p>Note: <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> must be enabled in order
to use this flag.</p>
</li>
'<strong><code>passthrough|PT</code></strong>'
(<strong>p</strong>ass <strong>t</strong>hrough to next
handler)<br />
- This flag forces the rewriting engine to set the
+ 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
- be able to post-process the output of
- <code>RewriteRule</code> directives by
+ enable post-processing of the output of
+ <code>RewriteRule</code> directives, using
<code>Alias</code>, <code>ScriptAlias</code>,
- <code>Redirect</code>, <em>etc.</em> directives from
- other URI-to-filename translators. A trivial example to
- show the semantics: If you want to rewrite
- <code>/abc</code> to <code>/def</code> via the rewriting
- engine of <code>mod_rewrite</code> and then
- <code>/def</code> to <code>/ghi</code> with
- <code>mod_alias</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 then
- <code>mod_rewrite</code> will do its job fine,
- <em>i.e.</em>, it rewrites <code>uri=/abc/...</code> to
+ 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> comes and tries to do a
- URI-to-filename transition which will not work.
+ <code>mod_alias</code> will try to do a
+ URI-to-filename transition, which will fail.
- <p>Note: <strong>You have to use this flag if you want to
- intermix directives of different modules which contain
+ <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>mod_alias</code> and
- <code>mod_rewrite</code>..</p>
+ is the use of <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> and
+ <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
</li>
<li>'<strong><code>qsappend|QSA</code></strong>'
(<strong>q</strong>uery <strong>s</strong>tring
<strong>a</strong>ppend)<br />
- This flag forces the rewriting engine to append a query
- string part in the substitution string to the existing one
+ This flag forces the rewrite engine to append a query
+ string part of the substitution string to the existing string,
instead of replacing it. Use this when you want to add more
data to the query string via a rewrite rule.</li>
<li>'<strong><code>redirect|R</code>
[=<em>code</em>]</strong>' (force <a id="redirect" name="redirect"><strong>r</strong>edirect</a>)<br />
- Prefix <em>Substitution</em> with
+ 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) is used. If you want to use other response
- codes in the range 300-400 just specify them as a number
+ <em>code</em> is given, a HTTP response of 302 (MOVED
+ TEMPORARILY) will be returned. If you want to use other response
+ codes in the range 300-400, simply specify the appropriate number
or use one of the following symbolic names:
<code>temp</code> (default), <code>permanent</code>,
- <code>seeother</code>. Use it for rules which should
- canonicalize the URL and give it back to the client,
- <em>e.g.</em>, translate ``<code>/~</code>'' into
- ``<code>/u/</code>'' or always append a slash to
+ <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 />
-
-
- <p><strong>Note:</strong> When you use this flag, make
- sure that the substitution field is a valid URL! If not,
- you are redirecting to an invalid location! And remember
- that this flag itself only prefixes the URL with
- <code>http://thishost[:thisport]/</code>, rewriting
- continues. Usually you also want to stop and do the
- redirection immediately. To stop the rewriting you also
- have to provide the 'L' flag.</p>
+ <strong>Note:</strong> When you use this flag, make
+ sure that the substitution field is a valid URL! Otherwise,
+ you will be redirecting to an invalid location. Remember
+ that this flag on its own will only prepend
+ <code>http://thishost[:thisport]/</code> to the URL, and rewriting
+ will continue. Usually, you will want to stop rewriting at this point,
+ and redirect immediately. To stop rewriting, you should add
+ the 'L' flag.
</li>
<li>'<strong><code>skip|S</code></strong>=<em>num</em>'
(<strong>s</strong>kip next rule(s))<br />
- This flag forces the rewriting engine to skip the next
- <em>num</em> rules in sequence when the current rule
+ 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
+ <code>skip=N</code>, where N is the number of rules in the
else-clause. (This is <strong>not</strong> the same as the
'chain|C' flag!)</li>
'<strong><code>type|T</code></strong>=<em>MIME-type</em>'
(force MIME <strong>t</strong>ype)<br />
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>. For instance, this can be used to
- setup the content-type based on some conditions.
+ <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:
RewriteRule ^(.+\.php)s$ $1 [T=application/x-httpd-php-source]
</code></p></div>
</li>
-
-
</ul>
-<div class="note"><h3>Note</h3> Never forget that <em>Pattern</em> is
+<div class="note"><h3>Note: Enabling rewrites in per-directory context</h3>
+ To enable the rewrite engine
+ for per-directory configuration files you need to set
+ ``<code>RewriteEngine On</code>'' in these files
+ <strong>and</strong> ``<code>Options
+ FollowSymLinks</code>'' must be enabled. If your
+ administrator has disabled override of
+ <code>FollowSymLinks</code> for a user's directory, then
+ you cannot use the rewrite engine. This restriction is
+ required for security reasons.
+</div>
+
+<div class="note"><h3>Note: Pattern matching in per-directory context</h3>
+ Never forget that <em>Pattern</em> is
applied to a complete URL in per-server configuration
-files. <strong>But in per-directory configuration files, the
+files. <strong>However, in per-directory configuration files, the
per-directory prefix (which always is the same for a specific
-directory!) is automatically <em>removed</em> for the pattern matching
+directory) is automatically <em>removed</em> for the pattern matching
and automatically <em>added</em> after the substitution has been
-done.</strong> This feature is essential for many sorts of rewriting,
-because without this prefix stripping you have to match the parent
-directory which is not always possible.
+done.</strong> This feature is essential for many sorts of rewriting -
+without this, you would always have to match the parent
+directory, which is not always possible.
<p>There is one exception: If a substitution string
- starts with ``<code>http://</code>'' then the directory
- prefix will <strong>not</strong> be added and an
- external redirect or proxy throughput (if flag
- <strong>P</strong> is used!) is forced!</p>
+ 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!</p>
</div>
-<div class="note"><h3>Note</h3>
- To enable the rewriting engine
- for per-directory configuration files you need to set
- ``<code>RewriteEngine On</code>'' in these files
- <strong>and</strong> ``<code>Options
- FollowSymLinks</code>'' must be enabled. If your
- administrator has disabled override of
- <code>FollowSymLinks</code> for a user's directory, then
- you cannot use the rewriting engine. This restriction is
- needed for security reasons.
+<div class="note"><h3>Note: Substitution of Absolute URLs</h3>
+ <p>
+ When you prefix a substitution field with
+ <code>http://thishost[:thisport]</code>, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> will automatically strip that
+ out. This auto-reduction on URLs with an implicit
+ external redirect is most useful in
+ combination with a mapping-function which generates the
+ hostname part.</p>
+
+ <p><strong>Remember:</strong> An unconditional external
+ redirect to your own server will not work with the prefix
+ <code>http://thishost</code> because of this feature. To
+ achieve such a self-redirect, you have to use the
+ <strong>R</strong>-flag.</p>
+</div>
+
+<div class="note"><h3>Note: Query String</h3>
+ <p>The <em>Pattern</em> will not be matched against the query string.
+ To do this, you must use a <code class="directive"><a href="#rewritecond">RewriteCond</a></code> with the
+ <code>%{QUERY_STRING}</code> variable. You can, however, create
+ URLs in the substitution string, containing a query string
+ part. Simply use a question mark inside the substitution string, to
+ indicate that the following text should be re-injected into the
+ query string. When you want to erase an existing query string,
+ end the substitution string with just a question mark. To
+ combine new and old query strings, use the
+ <code>[QSA]</code> flag.</p>
</div>
-
<p>Here are all possible substitution combinations and their
+ <p>Here are all possible substitution combinations and their
meanings:</p>
<p><strong>Inside per-server configuration
<div class="note"><pre>
<strong>Given Rule</strong> <strong>Resulting Substitution</strong>
---------------------------------------------- ----------------------------------
-^/somepath(.*) otherpath$1 not supported, because invalid!
+^/somepath(.*) otherpath$1 invalid, not supported
-^/somepath(.*) otherpath$1 [R] not supported, because invalid!
+^/somepath(.*) otherpath$1 [R] invalid, not supported
-^/somepath(.*) otherpath$1 [P] not supported, because invalid!
+^/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] not supported, because silly!
+^/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] not supported, because silly!
+^/somepath(.*) http://thishost/otherpath$1 [P] doesn't make sense, not supported
---------------------------------------------- ----------------------------------
^/somepath(.*) http://otherhost/otherpath$1 http://otherhost/otherpath/pathinfo
via external redirection
<p><strong>Inside per-directory configuration for
<code>/somepath</code><br />
- (<em>i.e.</em>, file <code>.htaccess</code> in dir
- <code>/physical/path/to/somepath</code> containing
+ (<code>/physical/path/to/somepath/.htacccess</code>, with
<code>RewriteBase /somepath</code>)<br />
for request ``<code>GET
/somepath/localpath/pathinfo</code>'':</strong><br />
^localpath(.*) otherpath$1 [R] http://thishost/somepath/otherpath/pathinfo
via external redirection
-^localpath(.*) otherpath$1 [P] not supported, because silly!
+^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] not supported, because silly!
+^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] not supported, because silly!
+^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$1 [P] http://otherhost/otherpath/pathinfo
via internal proxy
</pre></div>
-
- <p><strong>Example:</strong></p>
-
- <p>We want to rewrite URLs of the form </p>
-
- <p class="indent">
- <code>/</code> <em>Language</em> <code>/~</code>
- <em>Realname</em> <code>/.../</code> <em>File</em>
- </p>
-
- <p>into </p>
-
- <p class="indent">
- <code>/u/</code> <em>Username</em> <code>/.../</code>
- <em>File</em> <code>.</code> <em>Language</em>
- </p>
-
- <p>We take the rewrite mapfile from above and save it under
- <code>/path/to/file/map.txt</code>. Then we only have to
- add the following lines to the Apache server configuration
- file:</p>
-
-<div class="example"><pre>
-RewriteLog /path/to/file/rewrite.log
-RewriteMap real-to-user txt:/path/to/file/map.txt
-RewriteRule ^/([^/]+)/~([^/]+)/(.*)$ /u/${real-to-user:$2|nobody}/$3.$1
-</pre></div>
</div>
</div>
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