path: root/docs/manual/mod/mod_alias.xml

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<modulesynopsis metafile="mod_alias.xml.meta">

<name>mod_alias</name>
<description>Provides for mapping different parts of the host
    filesystem in the document tree and for URL redirection</description>
<status>Base</status>
<sourcefile>mod_alias.c</sourcefile>
<identifier>alias_module</identifier>

<summary>
    <p>The directives contained in this module allow for manipulation
    and control of URLs as requests arrive at the server. The
    <directive module="mod_alias">Alias</directive> and <directive
    module="mod_alias">ScriptAlias</directive> directives are used to
    map between URLs and filesystem paths.  This allows for content
    which is not directly under the <directive
    module="core">DocumentRoot</directive> served as part of the web
    document tree. The <directive
    module="mod_alias">ScriptAlias</directive> directive has the
    additional effect of marking the target directory as containing
    only CGI scripts.</p>

    <p>The <directive module="mod_alias">Redirect</directive>
    directives are used to instruct clients to make a new request with
    a different URL. They are often used when a resource has moved to
    a new location.</p>

    <p><module>mod_alias</module> is designed to handle simple URL
    manipulation tasks.  For more complicated tasks such as
    manipulating the query string, use the tools provided by
    <module>mod_rewrite</module>.</p>

</summary>

<seealso><module>mod_rewrite</module></seealso> <seealso><a
href="../urlmapping.html">Mapping URLs to the filesystem</a></seealso>

<section id="order"><title>Order of Processing</title>

<p>Aliases and Redirects occuring in different contexts are processed
like other directives according to standard <a
href="../sections.html#mergin">merging rules</a>.  But when multiple
Aliases or Redirects occur in the same context (for example, in the
same <directive type="section" module="core">VirtualHost</directive>
section) they are processed in a particular order.</p>

<p>First, all Redirects are processed before Aliases are processed,
and therefore a request that matches a <directive
module="mod_alias">Redirect</directive> or <directive
module="mod_alias">RedirectMatch</directive> will never have Aliases
applied.  Second, the Aliases and Redirects are processed in the order
they appear in the configuration files, with the first match taking
precedence.</p>

<p>For this reason, when two or more of these directives apply to the
same sub-path, you must list the most specific path first in order for
all the directives to have an effect.  For example, the following
configuration will work as expected:</p>

<example>
Alias /foo/bar /baz<br />
Alias /foo /gaq
</example>

<p>But if the above two directives were reversed in order, the
<code>/foo</code> <directive module="mod_alias">Alias</directive>
would always match before the <code>/foo/bar</code> <directive
module="mod_alias">Alias</directive>, so the latter directive would be
ignored.</p>

</section>

<directivesynopsis>
<name>Alias</name>
<description>Maps URLs to filesystem locations</description>
<syntax>Alias <var>URL-path</var>
<var>file-path</var>|<var>directory-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>

<usage>

    <p>The <directive>Alias</directive> directive allows documents to
    be stored in the local filesystem other than under the 
    <directive module="core">DocumentRoot</directive>. URLs with a
    (%-decoded) path beginning with <var>url-path</var> will be mapped
    to local files beginning with <var>directory-path</var>.</p>

    <example><title>Example:</title>
      Alias /image /ftp/pub/image
    </example>

    <p>A request for http://myserver/image/foo.gif would cause the
    server to return the file /ftp/pub/image/foo.gif.  Only complete
    path segments are matched, so the above alias would not match a
    request for http://myserver/imagefoo.gif.  For more complex
    matching using regular expressions, see the <directive
    module="mod_alias">AliasMatch</directive> directive.</p>

    <p>Note that if you include a trailing / on the
    <var>url-path</var> then the server will require a trailing / in
    order to expand the alias. That is, if you use <code>Alias
    /icons/ /usr/local/apache/icons/</code> then the url
    <code>/icons</code> will not be aliased.</p>

    <p>Note that you may need to specify additional <directive
    type="section" module="core">Directory</directive> sections which
    cover the <em>destination</em> of aliases.  Aliasing occurs before
    <directive type="section" module="core">Directory</directive> sections
    are checked, so only the destination of aliases are affected.
    (Note however <directive type="section" module="core">Location</directive>
    sections are run through once before aliases are performed, so
    they will apply.)</p>

    <p>In particular, if you are creating an <code>Alias</code> to a
    directory outside of your <directive
    module="core">DocumentRoot</directive>, you may need to explicitly
    permit access to the target directory.</p>

    <example><title>Example:</title>
        Alias /image /ftp/pub/image<br />
        &lt;Directory /ftp/pub/image&gt;<br />
        <indent>
            Order allow,deny<br />
            Allow from all<br />
        </indent>
        &lt;/Directory&gt;
    </example>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>AliasMatch</name>
<description>Maps URLs to filesystem locations using regular 
expressions</description>
<syntax>AliasMatch <var>regex</var>
<var>file-path</var>|<var>directory-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>

<usage>
    <p>This directive is equivalent to <directive
    module="mod_alias">Alias</directive>, but makes use of 
    <glossary ref="regex">regular expressions</glossary>, 
    instead of simple prefix matching. The
    supplied regular expression is matched against the URL-path, and
    if it matches, the server will substitute any parenthesized
    matches into the given string and use it as a filename. For
    example, to activate the <code>/icons</code> directory, one might
    use:</p>

    <example>
      AliasMatch ^/icons(.*) /usr/local/apache/icons$1
    </example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>Redirect</name>
<description>Sends an external redirect asking the client to fetch
a different URL</description>
<syntax>Redirect [<var>status</var>] <var>URL-path</var>
<var>URL</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>FileInfo</override>

<usage>
    <p>The Redirect directive maps an old URL into a new one by asking
    the client to refetch the resource at the new location.</p>

    <p>The old <em>URL-path</em> is a (%-decoded) path beginning with
    a slash.  A relative path is not allowed.  The new <em>URL</em>
    should be an absolute URL beginning with a scheme and hostname,
    but a URL-path beginning with a slash may also be used, in which
    case the scheme and hostname of the current server will be
    added.</p>

    <p>Then any request beginning with <em>URL-Path</em> will return a
    redirect request to the client at the location of the target
    <em>URL</em>.  Additional path information beyond the matched
    <em>URL-Path</em> will be appended to the target URL.</p>

    <example><title>Example:</title>
      Redirect /service http://foo2.example.com/service
    </example>

    <p>If the client requests http://example.com/service/foo.txt, it
    will be told to access http://foo2.example.com/service/foo.txt
    instead.  Only complete path segments are matched, so the above
    example would not match a request for
    http://example.com/servicefoo.txt.  For more complex matching
    using regular expressions, see the <directive
    module="mod_alias">RedirectMatch</directive> directive.</p>


<note><title>Note</title> <p>Redirect directives take precedence over
Alias and ScriptAlias directives, irrespective of their ordering in
the configuration file.</p></note>

    <p>If no <var>status</var> argument is given, the redirect will
    be "temporary" (HTTP status 302). This indicates to the client
    that the resource has moved temporarily. The <var>status</var>
    argument can be used to return other HTTP status codes:</p>

    <dl>
      <dt>permanent</dt>

      <dd>Returns a permanent redirect status (301) indicating that
      the resource has moved permanently.</dd>

      <dt>temp</dt>

      <dd>Returns a temporary redirect status (302). This is the
      default.</dd>

      <dt>seeother</dt>

      <dd>Returns a "See Other" status (303) indicating that the
      resource has been replaced.</dd>

      <dt>gone</dt>

      <dd>Returns a "Gone" status (410) indicating that the
      resource has been permanently removed. When this status is
      used the <var>URL</var> argument should be omitted.</dd>
    </dl>

    <p>Other status codes can be returned by giving the numeric
    status code as the value of <var>status</var>. If the status is
    between 300 and 399, the <var>URL</var> argument must be present,
    otherwise it must be omitted. Note that the status must be
    known to the Apache code (see the function
    <code>send_error_response</code> in http_protocol.c).</p>

    <example><title>Example:</title>
      Redirect permanent /one http://example.com/two<br />
      Redirect 303 /three http://example.com/other
    </example>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>RedirectMatch</name>
<description>Sends an external redirect based on a regular expression match 
of the current URL</description>
<syntax>RedirectMatch [<var>status</var>] <var>regex</var>
<var>URL</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>FileInfo</override>

<usage>
    <p>This directive is equivalent to <directive
    module="mod_alias">Redirect</directive>, but makes use of 
    <glossary ref="regex">regular expressions</glossary>, 
    instead of simple prefix matching. The
    supplied regular expression is matched against the URL-path, and
    if it matches, the server will substitute any parenthesized
    matches into the given string and use it as a filename. For
    example, to redirect all GIF files to like-named JPEG files on
    another server, one might use:</p>

    <example>
      RedirectMatch (.*)\.gif$ http://www.anotherserver.com$1.jpg
    </example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>RedirectTemp</name>
<description>Sends an external temporary redirect asking the client to fetch
a different URL</description>
<syntax>RedirectTemp <var>URL-path</var> <var>URL</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>FileInfo</override>

<usage>
    <p>This directive makes the client know that the Redirect is
    only temporary (status 302). Exactly equivalent to
    <code>Redirect temp</code>.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>RedirectPermanent</name>
<description>Sends an external permanent redirect asking the client to fetch
a different URL</description>
<syntax>RedirectPermanent <var>URL-path</var> <var>URL</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context></contextlist>
<override>FileInfo</override>

<usage>
    <p>This directive makes the client know that the Redirect is
    permanent (status 301). Exactly equivalent to <code>Redirect
    permanent</code>.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ScriptAlias</name>
<description>Maps a URL to a filesystem location and designates the
target as a CGI script</description>
<syntax>ScriptAlias <var>URL-path</var>
<var>file-path</var>|<var>directory-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>

<usage>
    <p>The <directive>ScriptAlias</directive> directive has the same
    behavior as the <directive module="mod_alias">Alias</directive>
    directive, except that in addition it marks the target directory
    as containing CGI scripts that will be processed by <module
    >mod_cgi</module>'s cgi-script handler. URLs with a
    (%-decoded) path beginning with <var>URL-path</var> will be mapped
    to scripts beginning with the second argument which is a full
    pathname in the local filesystem.</p>

    <example><title>Example:</title>
      ScriptAlias /cgi-bin/ /web/cgi-bin/
    </example>

    <p>A request for <code>http://myserver/cgi-bin/foo</code> would cause the
    server to run the script <code>/web/cgi-bin/foo</code>.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>ScriptAliasMatch</name>
<description>Maps a URL to a filesystem location using a regular expression
and designates the target as a CGI script</description>
<syntax>ScriptAliasMatch <var>regex</var>
<var>file-path</var>|<var>directory-path</var></syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>

<usage>
    <p>This directive is equivalent to <directive module="mod_alias"
    >ScriptAlias</directive>, but makes use of 
    <glossary ref="regex">regular expressions</glossary>, 
    instead of simple prefix matching. The
    supplied regular expression is matched against the URL-path,
    and if it matches, the server will substitute any parenthesized
    matches into the given string and use it as a filename. For
    example, to activate the standard <code>/cgi-bin</code>, one
    might use:</p>

    <example>
      ScriptAliasMatch ^/cgi-bin(.*) /usr/local/apache/cgi-bin$1
    </example>
</usage>
</directivesynopsis>

</modulesynopsis>