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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>
<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>When the <directive module="mod_alias">Alias</directive>,
<directive module="mod_alias">ScriptAlias</directive> and
<directive module="mod_alias">Redirect</directive> directives are used
within a <directive type="section" module="core">Location</directive>
or <directive type="section" module="core">LocationMatch</directive>
to manipulate the destination path or URL.
</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
<section id="order"><title>Order of Processing</title>
<p>Aliases and Redirects occurring 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>
<highlight language="config">
Alias "/foo" "/gaq"
</highlight>
<p>But if the above two directives were reversed in order, the
<code>/foo</code> <directive module="mod_alias">Alias</directive>
module="mod_alias">Alias</directive>, so the latter directive would be
ignored.</p>
<p>When the <directive module="mod_alias">Alias</directive>,
<directive module="mod_alias">ScriptAlias</directive> and
<directive module="mod_alias">Redirect</directive> directives are used
within a <directive type="section" module="core">Location</directive>
or <directive type="section" module="core">LocationMatch</directive>
section, these directives will take precedence over any globally
defined <directive module="mod_alias">Alias</directive>,
<directive module="mod_alias">ScriptAlias</directive> and
<directive module="mod_alias">Redirect</directive> directives.</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>
<context>directory</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>. The
<var>URL-path</var> is case-sensitive, even on case-insensitive
file systems.</p>
<highlight language="config">
</highlight>
complete path segments are matched, so the above alias would not match a
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</p>
<highlight language="config">
</highlight>
<p>then the url <code>/icons</code> will not be aliased, as it lacks
that trailing /. Likewise, if you omit the slash on the
<var>URL-path</var> then you must also omit it from the
<var>file-path</var>.</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>
<highlight language="config">
Require all granted
</Directory>
</highlight>
<p>Any number slashes in the <var>URL-path</var> parameter
matches any number of slashes in the requested URL-path.</p>
<p>If the <directive>Alias</directive> directive is used within a
<directive type="section" module="core">Location</directive>
or <directive type="section" module="core">LocationMatch</directive>
section the URL-path is omitted, and the file-path is interpreted
<highlight language="config">
<Location "/image">
</Location>
<LocationMatch "/error/(?<NUMBER>[0-9]+)">
</LocationMatch>
</highlight>
</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>
<highlight language="config">
</highlight>
<p>The full range of <glossary ref="regex">regular expression</glossary>
power is available. For example,
it is possible to construct an alias with case-insensitive
matching of the URL-path:</p>
<highlight language="config">
</highlight>
<p>One subtle difference
between <directive module="mod_alias">Alias</directive>
and <directive module="mod_alias">AliasMatch</directive> is
that <directive module="mod_alias">Alias</directive> will
automatically copy any additional part of the URI, past the part
that matched, onto the end of the file path on the right side,
while <directive module="mod_alias">AliasMatch</directive> will
not. This means that in almost all cases, you will want the
regular expression to match the entire request URI from beginning
to end, and to use substitution on the right side.</p>
<p>In other words, just changing
<directive module="mod_alias">Alias</directive> to
<directive module="mod_alias">AliasMatch</directive> will not
have the same effect. At a minimum, you need to
add <code>^</code> to the beginning of the regular expression
and add <code>(.*)$</code> to the end, and add <code>$1</code> to
the end of the replacement.</p>
<p>For example, suppose you want to replace this with AliasMatch:</p>
<highlight language="config">
</highlight>
<p>This is NOT equivalent - don't do this! This will send all
<highlight language="config">
</highlight>
<p>This is what you need to get the same effect:</p>
<highlight language="config">
</highlight>
<p>Of course, there's no point in
using <directive module="mod_alias">AliasMatch</directive>
where <directive module="mod_alias">Alias</directive> would
work. <directive module="mod_alias">AliasMatch</directive> lets
you do more complicated things. For example, you could
serve different kinds of files from different directories:</p>
<highlight language="config">
</highlight>
<p>Multiple leading slashes in the requested URL are discarded
by the server before directives from this module compares
against the requested URL-path.
</p>
</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 case-sensitive (%-decoded) path
beginning with a slash. A relative path is not allowed.</p>
<p>The new <em>URL</em> may be either an absolute URL beginning
with a scheme and hostname, or a URL-path beginning with a slash.
In this latter 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>
<highlight language="config">
# Redirect to a URL on a different host
Redirect "/service" "http://foo2.example.com/service"
# Redirect to a URL on the same host
Redirect "/one" "/two"
</highlight>
it will be told to access
instead. This includes requests with <code>GET</code> parameters, such as
it will be redirected to
Note that <code>POST</code>s will be discarded.<br />
Only complete path segments are matched, so the above
example would not match a request for
argument as described below. Alternatively, for 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. Redirect directives inside a Location take precedence over
Redirect and Alias directives with an URL-path.</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.
If the status is <em>not</em> between 300 and 399, the
<var>URL</var> argument must be omitted. The status must be a valid
HTTP status code, known to the Apache HTTP Server (see the function
<highlight language="config">
Redirect permanent "/one" "http://example.com/two"
Redirect 303 "/three" "http://example.com/other"
</highlight>
<p>If the <directive>Redirect</directive> directive is used within a
<directive type="section" module="core">Location</directive>
or <directive type="section" module="core">LocationMatch</directive>
section with the URL-path omitted, then the URL parameter will be
<highlight language="config">
<Location "/one">
Redirect permanent "http://example.com/two"
</Location><br />
<Location "/three">
Redirect 303 "http://example.com/other"
</Location><br />
<LocationMatch "/error/(?<NUMBER>[0-9]+)">
Redirect permanent "http://example.com/errors/%{env:MATCH_NUMBER}.html"
</LocationMatch><br />
</highlight>
</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>
<highlight language="config">
RedirectMatch "(.*)\.gif$" "http://other.example.com$1.jpg"
</highlight>
<p>The considerations related to the difference between
<directive module="mod_alias">Alias</directive> and
<directive module="mod_alias">AliasMatch</directive>
also apply to the difference between
<directive module="mod_alias">Redirect</directive> and
<directive module="mod_alias">RedirectMatch</directive>.
See <directive module="mod_alias">AliasMatch</directive> for
details.</p>
</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>
<context>directory</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 case-sensitive
(%-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>
<highlight language="config">
</highlight>
is essentially equivalent to:</p>
<highlight language="config">
<Location "/cgi-bin">
SetHandler cgi-script
Options +ExecCGI
</Location>
</highlight>
<p><directive>ScriptAlias</directive> can also be used in conjunction with
a script or handler you have. For example:</p>
<highlight language="config">
ScriptAlias "/cgi-bin/" "/web/cgi-handler.pl"
</highlight>
<p>In this scenario all files requested in <code>/cgi-bin/</code> will be
handled by the file you have configured, this allows you to use your own custom
handler. You may want to use this as a wrapper for CGI so that you can add
content, or some other bespoke action.</p>
<note type="warning">It is safer to avoid placing CGI scripts under the
<directive module="core">DocumentRoot</directive> in order to
avoid accidentally revealing their source code if the
configuration is ever changed. The
<directive>ScriptAlias</directive> makes this easy by mapping a
URL and designating CGI scripts at the same time. If you do
choose to place your CGI scripts in a directory already
accessible from the web, do not use
<directive>ScriptAlias</directive>. Instead, use <directive
module="core" type="section">Directory</directive>, <directive
module="core">SetHandler</directive>, and <directive
module="core">Options</directive> as in:
<highlight language="config">
SetHandler cgi-script
Options ExecCGI
</Directory>
</highlight>
This is necessary since multiple <var>URL-paths</var> can map
to the same filesystem location, potentially bypassing the
<directive>ScriptAlias</directive> and revealing the source code
of the CGI scripts if they are not restricted by a
<directive module="core">Directory</directive> section.</note>
<p>If the <directive>ScriptAlias</directive> directive is used within
a <directive type="section" module="core">Location</directive>
or <directive type="section" module="core">LocationMatch</directive>
section with the URL-path omitted, then the URL parameter will be
<highlight language="config">
<Location "/cgi-bin">
</Location>
</LocationMatch><br />
</highlight>
</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>
<highlight language="config">
</highlight>
<p>As for AliasMatch, the full range of <glossary ref="rexex">regular
expression</glossary> power is available.
For example, it is possible to construct an alias with case-insensitive
matching of the URL-path:</p>
<highlight language="config">
</highlight>
<p>The considerations related to the difference between
<directive module="mod_alias">Alias</directive> and
<directive module="mod_alias">AliasMatch</directive>
also apply to the difference between
<directive module="mod_alias">ScriptAlias</directive> and
<directive module="mod_alias">ScriptAliasMatch</directive>.
See <directive module="mod_alias">AliasMatch</directive> for
details.</p>
</usage>
</directivesynopsis>
</modulesynopsis>