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  &project;

  <properties>
    <author email="remm@apache.org">Remy Maucherat</author>
    <title>The rewrite Valve</title>
  </properties>

<body>

<section name="Introduction">

  <p>The rewrite valve implements URL rewrite functionality in a way that is
  very similar to mod_rewrite from Apache HTTP Server.</p>

</section>

<section name="Configuration">

  <p>The rewrite valve is configured as a valve using the <code>org.apache.catalina.valves.rewrite.RewriteValve</code>
  class name.</p>

  <p>The rewrite valve can be configured as a valve added in a Host.
     See <a href="config/host.html">virtual-server</a> documentation for
     informations how to configure it. It will use a <code>rewrite.config</code> file
     containing the rewrite directives, it must be placed in the Host configuration
     folder.
  </p>

  <p>It can also be in the context.xml of a webapp.
  The valve will then use a <code>rewrite.config</code> file containing the
  rewrite directives, it must be placed in the WEB-INF folder of the web application
  </p>

</section>

<section name="Directives">

  <p>The rewrite.config file contains a list of directives which closely
  resemble the directives used by mod_rewrite, in particular the central
  RewriteRule and RewriteCond directives. Lines that start with a
  <code>#</code> character are treated as comments and will be ignored.</p>

  <p>Note: This section is a modified version of the mod_rewrite documentation,
  which is Copyright 1995-2006 The Apache Software Foundation, and licensed under the
  under the Apache License, Version 2.0.</p>

  <subsection name="RewriteCond">

    <p>Syntax: <code>RewriteCond TestString CondPattern</code></p>

    <p>The RewriteCond directive defines a rule condition. One or more RewriteCond
    can precede a RewriteRule directive. The following rule is then only used if both
    the current state of the URI matches its pattern, and 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:

          <ul>
          <li>
          <p><b>HTTP headers:</b></p>
          <p>
            HTTP_USER_AGENT<br />
            HTTP_REFERER<br />
            HTTP_COOKIE<br />
            HTTP_FORWARDED<br />
            HTTP_HOST<br />
            HTTP_PROXY_CONNECTION<br />
            HTTP_ACCEPT<br />
          </p>
          </li>
          <li>
          <p><b>connection &amp; request:</b></p>
          <p>
            REMOTE_ADDR<br />
            REMOTE_HOST<br />
            REMOTE_PORT<br />
            REMOTE_USER<br />
            REMOTE_IDENT<br />
            REQUEST_METHOD<br />
            SCRIPT_FILENAME<br />
            REQUEST_PATH<br />
            CONTEXT_PATH<br />
            SERVLET_PATH<br />
            PATH_INFO<br />
            QUERY_STRING<br />
            AUTH_TYPE<br />
          </p>
          </li>
          <li>
          <p><b>server internals:</b></p>
          <p>
            DOCUMENT_ROOT<br />
            SERVER_NAME<br />
            SERVER_ADDR<br />
            SERVER_PORT<br />
            SERVER_PROTOCOL<br />
            SERVER_SOFTWARE<br />
          </p>
          </li>
          <li>
          <p><b>date and time:</b></p>
          <p>
            TIME_YEAR<br />
            TIME_MON<br />
            TIME_DAY<br />
            TIME_HOUR<br />
            TIME_MIN<br />
            TIME_SEC<br />
            TIME_WDAY<br />
            TIME<br />
          </p>
          </li>
          <li>
          <p><b>specials:</b></p>
          <p>
            THE_REQUEST<br />
            REQUEST_URI<br />
            REQUEST_FILENAME<br />
            HTTPS<br />
          </p>
          </li>
          </ul>

                <p>These variables all
                correspond to the similarly named HTTP
                MIME-headers and Servlet API methods.
                Most are documented elsewhere in the Manual or in
                the CGI specification. Those that are special to
                the rewrite valve include those below.</p>

                <dl>

                  <dt><code>REQUEST_PATH</code></dt>

                  <dd>Corresponds to the full path that is used for mapping.</dd>

                  <dt><code>CONTEXT_PATH</code></dt>

                  <dd>Corresponds to the path of the mapped context.</dd>

                  <dt><code>SERVLET_PATH</code></dt>

                  <dd>Corresponds to the servlet path.</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 file system 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.</dd>

                </dl>

        </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 Java system property, is also available.</li>

        <li>
        <code>%{SSL:variable}</code>, where <em>variable</em> is the
        name of an SSL environment
        variable, are not implemented yet.  Example:
        <code>%{SSL:SSL_CIPHER_USEKEYSIZE}</code> may expand to
        <code>128</code>.</li>

        <li>
        <code>%{HTTP:header}</code>, where <em>header</em> can be
        any HTTP MIME-header name, can always be used to obtain the
        value of a header sent in the HTTP request.
        Example: <code>%{HTTP:Proxy-Connection}</code> is
        the value of the HTTP header
        ``<code>Proxy-Connection:</code>''.</li>

      </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>

          </ul>

<strong>Note:</strong>
              All of these tests can
              also be prefixed by an exclamation mark ('!') to
              negate their meaning.

        </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 file system 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:

<source>RewriteCond %{REMOTE_HOST}  ^host1.*  [OR]
RewriteCond %{REMOTE_HOST}  ^host2.*  [OR]
RewriteCond %{REMOTE_HOST}  ^host3.*
RewriteRule ...some special stuff for any of these hosts...</source>

          Without this flag you would have to write the condition/rule
          pair three times.
        </li>
      </ul>
      </li>
     </ol>

      <p><strong>Example:</strong></p>

       <p>To rewrite the Homepage of a site according to the
        ``<code>User-Agent:</code>'' header of the request, you can
        use the following: </p>

<source>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]</source>

        <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>

  </subsection>

  <subsection name="RewriteMap">

    <p>Syntax: <code>RewriteMap name rewriteMapClassName optionalParameters</code></p>

    <p>The maps are implemented using an interface that users must implement. Its class
    name is <code>org.apache.catalina.valves.rewrite.RewriteMap</code>, and its code is:</p>

<source><![CDATA[package org.apache.catalina.valves.rewrite;

public interface RewriteMap {
    public String setParameters(String params);
    public String lookup(String key);
}]]></source>

  </subsection>

  <subsection name="RewriteRule">

    <p>Syntax: <code>RewriteRule Pattern Substitution</code></p>

      <p>The RewriteRule 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>Pattern is a perl compatible regular
      expression, which is applied to the current URL.
      ``Current'' means the value of the URL when this rule is
      applied. This may not be the originally requested URL,
      which may already have matched a previous rule, and have been
      altered.</p>

      <p><strong>Security warning:</strong> Due to the way Java's
      regex matching is done, poorly formed regex patterns are vulnerable
      to "catastrophic backtracking", also known as "regular expression
      denial of service" or ReDoS. Therefore, extra caution should be used
      for RewriteRule patterns. In general it is difficult to automatically
      detect such vulnerable regex, and so a good defense is to read a bit
      on the subject of catastrophic backtracking. A good reference is the
      <a href="https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS">
      OWASP ReDoS guide</a>.</p>

      <p>Some hints on the syntax of regular
      expressions:</p>

<!-- TODO: Why is the following pre-formatted non-wrappable text? -->
<pre>
<strong>Text:</strong>
  <strong><code>.</code></strong>           Any single character
  <strong><code>[</code></strong>chars<strong><code>]</code></strong>     Character class: Any character of the class ``chars''
  <strong><code>[^</code></strong>chars<strong><code>]</code></strong>    Character class: Not a character of the class ``chars''
  text1<strong><code>|</code></strong>text2 Alternative: text1 or text2

<strong>Quantifiers:</strong>
  <strong><code>?</code></strong>           0 or 1 occurrences of the preceding text
  <strong><code>*</code></strong>           0 or N occurrences of the preceding text (N &gt; 0)
  <strong><code>+</code></strong>           1 or N occurrences of the preceding text (N &gt; 1)

<strong>Grouping:</strong>
  <strong><code>(</code></strong>text<strong><code>)</code></strong>      Grouping of text
              (used either to set the borders of an alternative as above, or
              to make backreferences, where the <strong>N</strong>th group can
              be referred to on the RHS of a RewriteRule as <code>$</code><strong>N</strong>)

<strong>Anchors:</strong>
  <strong><code>^</code></strong>           Start-of-line anchor
  <strong><code>$</code></strong>           End-of-line anchor

<strong>Escaping:</strong>
  <strong><code>\</code></strong>char       escape the given char
              (for instance, to specify the chars "<code>.[]()</code>" <em>etc.</em>)
</pre>

      <p>For more information about regular expressions, have a look at the
      perl regular expression manpage ("<a
      href="https://perldoc.perl.org/perlre.html">perldoc
      perlre</a>"). If you are interested in more detailed
      information about regular expressions and their variants
      (POSIX regex etc.) the following book is dedicated to this topic:</p>

      <p class="indent">
        <em>Mastering Regular Expressions, 2nd Edition</em><br />
         Jeffrey E.F. Friedl<br />
         O'Reilly &amp; Associates, Inc. 2002<br />
         ISBN 978-0-596-00289-3<br />
      </p>

      <p>In the rules, 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>

<p>
Note: 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 (i.e., 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!
</p>

      <p>The <em id="rhs" >substitution</em> of a
      rewrite rule is the string which is substituted for (or
      replaces) the original URL which <em>Pattern</em>
      matched. In addition to plain text, it can include</p>

      <ol>
        <li>back-references (<code>$N</code>) to the RewriteRule
        pattern</li>

        <li>back-references (<code>%N</code>) to the last matched
        RewriteCond pattern</li>

        <li>server-variables as in rule condition test-strings
        (<code>%{VARNAME}</code>)</li>

        <li><a href="#mapfunc">mapping-function</a> calls
        (<code>${mapname:key|default}</code>)</li>
      </ol>
      <p>Back-references are identifiers of the form
      <code>$</code><strong>N</strong>
      (<strong>N</strong>=0..9), which will be replaced
      by the contents of the <strong>N</strong>th group of the
      matched <em>Pattern</em>. The server-variables are the same
      as for the <em>TestString</em> of a <code>RewriteCond</code>
      directive. The mapping-functions come from the
      <code>RewriteMap</code> directive and are explained there.
      These three types of variables are expanded in the order above.</p>

      <p>As already mentioned, all rewrite rules are
      applied to the <em>Substitution</em> (in the order in which
      they are defined
      in the config file). The URL is <strong>completely
      replaced</strong> by the <em>Substitution</em> and the
      rewriting process continues until all rules have been applied,
      or it is explicitly terminated by a
      <code><strong>L</strong></code> flag.</p>

      <p>The special characters <code>$</code> and <code>%</code> can
      be quoted by prepending them with a backslash character
      <code>\</code>.</p>

      <p>There is a special substitution string named
      '<code>-</code>' which means: <strong>NO
      substitution</strong>! This is useful in providing
      rewriting rules which <strong>only</strong> match
      URLs but do not substitute anything for them. It is commonly used
      in conjunction with the <strong>C</strong> (chain) flag, in order
      to apply more than one pattern before substitution occurs.</p>

      <p>Unlike newer mod_rewrite versions, the Tomcat rewrite valve does
      not automatically support absolute URLs (the specific redirect flag
      must be used to be able to specify an absolute URLs, see below)
      or direct file serving.</p>

      <p>Additionally you can set special <span
      id="rewriteflags">flags</span> for <em>Substitution</em> by
      appending <strong><code>[</code><em>flags</em><code>]</code></strong>
      as the third argument to the <code>RewriteRule</code>
      directive. <em>Flags</em> is a comma-separated list of any of the
      following flags: </p>

      <ul>
        <li>'<strong><code>chain|C</code></strong>'
        (<strong>c</strong>hained with next rule)<br />
         This flag chains the current rule with the next rule
        (which itself can be chained with the following rule,
        and so on). This has the following effect: if a rule
        matches, then processing continues as usual -
        the flag has no effect. If the rule does
        <strong>not</strong> match, then all following chained
        rules are skipped. For instance, it can be used to remove the
        ``<code>.www</code>'' part, inside a per-directory rule set,
        when you let an external redirect happen (where the
        ``<code>.www</code>'' part should not occur!).</li>

        <li>
        '<strong><code>cookie|CO=</code></strong><em>NAME</em>:<em>VAL</em>:<em>domain</em>[:<em>lifetime</em>[:<em>path</em>]]'
        (set <strong>co</strong>okie)<br />
        This sets a cookie in the client's browser.  The cookie's name
        is specified by <em>NAME</em> and the value is
        <em>VAL</em>. The <em>domain</em> field is the domain of the
        cookie, such as '.apache.org', the optional <em>lifetime</em>
        is the lifetime of the cookie in minutes, and the optional
        <em>path</em> is the path of the cookie</li>

        <li>
        '<strong><code>env|E=</code></strong><em>VAR</em>:<em>VAL</em>'
        (set <strong>e</strong>nvironment variable)<br />
        This forces a request attribute 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.</li>

        <li>'<strong><code>forbidden|F</code></strong>' (force URL
        to be <strong>f</strong>orbidden)<br />
        This forces the current URL to be forbidden - it immediately
        sends back a HTTP response of 403 (FORBIDDEN).
        Use this flag in conjunction with
        appropriate RewriteConds to conditionally block some
        URLs.</li>

        <li>'<strong><code>gone|G</code></strong>' (force URL to be
        <strong>g</strong>one)<br />
        This forces the current URL to be gone - it
        immediately sends back a HTTP response of 410 (GONE). Use
        this flag to mark pages which no longer exist as gone.</li>

        <li>
        '<strong><code>host|H</code></strong>=<em>Host</em>'
        (apply rewriting to <strong>h</strong>ost)<br />
        Rather that rewrite the URL, the virtual host will be
        rewritten.</li>

        <li>'<strong><code>last|L</code></strong>'
        (<strong>l</strong>ast rule)<br />
        Stop the rewriting process here and don't apply any more
        rewrite rules. This corresponds to the Perl
        <code>last</code> command or the <code>break</code> command
        in C. Use this flag to prevent the currently
        rewritten URL from being rewritten further by following
        rules. For example, use it to rewrite the root-path URL
        ('<code>/</code>') to a real one, <em>e.g.</em>,
        '<code>/e/www/</code>'.</li>

        <li>'<strong><code>next|N</code></strong>'
        (<strong>n</strong>ext round)<br />
        Re-run the rewriting process (starting again with the
        first rewriting rule). This time, the URL to match is no longer
        the original URL, but rather the URL returned by the last rewriting rule.
        This corresponds to the Perl <code>next</code> command or
        the <code>continue</code> command in C. Use
        this flag to restart the rewriting process -
        to immediately go to the top of the loop.<br />
         <strong>Be careful not to create an infinite
        loop!</strong></li>

        <li>'<strong><code>nocase|NC</code></strong>'
        (<strong>n</strong>o <strong>c</strong>ase)<br />
        This makes the <em>Pattern</em> case-insensitive,
        ignoring difference between 'A-Z' and
        'a-z' when <em>Pattern</em> is matched against the current
        URL.</li>

        <li>
          '<strong><code>noescape|NE</code></strong>'
          (<strong>n</strong>o URI <strong>e</strong>scaping of
          output)<br />
          This flag prevents the rewrite valve 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
          <source>RewriteRule /foo/(.*) /bar?arg=P1\%3d$1 [R,NE]</source>
          which would turn '<code>/foo/zed</code>' into a safe
          request for '<code>/bar?arg=P1=zed</code>'.
        </li>

<!-- Not supported yet
        <li>
          '<strong><code>proxy|P</code></strong>' (force
          <strong>p</strong>roxy)<br />
          This flag forces the substitution part to be internally
          sent as a proxy request and immediately (rewrite
          processing stops here) put through the <a
          href="mod_proxy.html">proxy module</a>. You must make
          sure that the substitution string is a valid URI
          (typically starting with
          <code>http://</code><em>hostname</em>) which can be
          handled by the Apache proxy module. If not, you will get an
          error from the proxy module. Use this flag to achieve a
          more powerful implementation of the <a
          href="mod_proxy.html#proxypass">ProxyPass</a> directive,
          to map remote content into the namespace of the local
          server.

          <p>Note: <module>mod_proxy</module> must be enabled in order
          to use this flag.</p>
        </li>
        -->

        <li>'<strong><code>qsappend|QSA</code></strong>'
        (<strong>q</strong>uery <strong>s</strong>tring
        <strong>a</strong>ppend)<br />
        This flag forces the rewrite engine to append a query
        string part of the substitution string to the existing string,
        instead of replacing it. Use this when you want to add more
        data to the query string via a rewrite rule.</li>

         <li>'<strong><code>redirect|R</code>
          [=<em>code</em>]</strong>' (force <span id="redirect">
          <strong>r</strong>edirect</span>)<br />
          Prefix <em>Substitution</em> with
          <code>http://thishost[:thisport]/</code> (which makes the
          new URL a URI) to force a external redirection. If no
          <em>code</em> is given, a HTTP response of 302 (FOUND, previously MOVED
          TEMPORARILY) will be returned. If you want to use other response
          codes in the range 300-399, simply specify the appropriate number
          or use one of the following symbolic names:
          <code>temp</code> (default), <code>permanent</code>,
          <code>seeother</code>. Use this for rules to
          canonicalize the URL and return it to the client - to
          translate ``<code>/~</code>'' into
          ``<code>/u/</code>'', or to always append a slash to
          <code>/u/</code><em>user</em>, etc.<br />
          <strong>Note:</strong> When you use this flag, make
          sure that the substitution field is a valid URL! Otherwise,
          you will be redirecting to an invalid location. Remember
          that this flag on its own will only prepend
          <code>http://thishost[:thisport]/</code> to the URL, and rewriting
          will continue. Usually, you will want to stop rewriting at this point,
          and redirect immediately. To stop rewriting, you should add
          the 'L' flag.
        </li>

        <li>'<strong><code>skip|S</code></strong>=<em>num</em>'
        (<strong>s</strong>kip next rule(s))<br />
        This flag forces the rewriting engine to skip the next
        <em>num</em> rules in sequence, if the current rule
        matches. Use this to make pseudo if-then-else constructs:
        The last rule of the then-clause becomes
        <code>skip=N</code>, where N is the number of rules in the
        else-clause. (This is <strong>not</strong> the same as the
        'chain|C' flag!)</li>

        <li>
        '<strong><code>type|T</code></strong>=<em>MIME-type</em>'
        (force MIME <strong>t</strong>ype)<br />
         Force the MIME-type of the target file to be
        <em>MIME-type</em>. This can be used to
        set up the content-type based on some conditions.
        For example, the following snippet allows <code>.php</code> files to
        be <em>displayed</em> by <code>mod_php</code> if they are called with
        the <code>.phps</code> extension:
        <source>RewriteRule ^(.+\.php)s$ $1 [T=application/x-httpd-php-source]</source>
        </li>
      </ul>

  </subsection>

</section>

</body>
</document>
