Apache module mod_alias

### Apache HTTP Server Version 1.3

# Module mod_alias

This module provides for mapping different parts of the host filesystem in the document tree, and for URL redirection.

Status: Base
Source File: mod_alias.c
Module Identifier: alias_module

## Summary

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

The `Redirect` 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.

A more powerful and flexible set of directives for manipulating URLs is contained in the `mod_rewrite` module.

## Directives

- Alias
- AliasMatch
- Redirect
- RedirectMatch
- RedirectTemp
- RedirectPermanent
- ScriptAlias
- ScriptAliasMatch

## Alias directive

Syntax: Alias url-path directory-filename
Context: server config, virtual host
Status: Base
Module: mod_alias

The Alias directive allows documents to be stored in the local filesystem other than under the DocumentRoot. URLs with a (%-decoded) path beginning with url-path will be mapped to local files beginning with directory-filename.

Example:

> `Alias /image /ftp/pub/image`

A request for http://myserver/image/foo.gif would cause the server to return the file /ftp/pub/image/foo.gif.

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

Note that you may need to specify additional `<Directory>` sections which cover the destination of aliases. Aliasing occurs before `<Directory>` sections are checked, so only the destination of aliases are affected. (Note however `<Location>` sections are run through once before aliases are performed, so they will apply.)

See also ScriptAlias.

## AliasMatch

Syntax: AliasMatch regex directory-filename
Context: server config, virtual host
Status: Base
Module: mod_alias
Compatibility: Available in Apache 1.3 and later

This directive is equivalent to Alias, but makes use of standard regular expressions, instead of simple prefix matching. The supplied regular expression is matched against the URL, 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 `/icons` directory, one might use:

        AliasMatch ^/icons(.*) /usr/local/apache/icons$1

## Redirect directive

Syntax: Redirect [status] url-path url
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Base
Module: mod_alias
Compatibility: The directory and .htaccess context's are only available in versions 1.1 and later. The status argument is only available in Apache 1.2 or later.

The Redirect directive maps an old URL into a new one. The new URL is returned to the client which attempts to fetch it again with the new address. Url-path a (%-decoded) path; any requests for documents beginning with this path will be returned a redirect error to a new (%-encoded) url beginning with url.

Example:

> `Redirect /service http://foo2.bar.com/service`

If the client requests http://myserver/service/foo.txt, it will be told to access http://foo2.bar.com/service/foo.txt instead.

Note: Redirect directives take precedence over Alias and ScriptAlias directives, irrespective of their ordering in the configuration file. Also, Url-path must be an absolute path, not a relative path, even when used with .htaccess files or inside of <Directory> sections.

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

permanent
  Returns a permanent redirect status (301) indicating that the resource has moved permanently.
temp
  Returns a temporary redirect status (302). This is the default.
seeother
  Returns a "See Other" status (303) indicating that the resource has been replaced.
gone
  Returns a "Gone" status (410) indicating that the resource has been permanently removed. When this status is used the url argument should be omitted.

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

## RedirectMatch

Syntax: RedirectMatch [status] regex url
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Base
Module: mod_alias
Compatibility: Available in Apache 1.3 and later

This directive is equivalent to Redirect, but makes use of standard regular expressions, instead of simple prefix matching. The supplied regular expression is matched against the URL, 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:

        RedirectMatch (.*)\.gif$ http://www.anotherserver.com$1.jpg

## RedirectTemp directive

Syntax: RedirectTemp url-path url
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Base
Module: mod_alias
Compatibility: This directive is only available in Apache 1.2 and later

This directive makes the client know that the Redirect is only temporary (status 302). Exactly equivalent to `Redirect temp`.

## RedirectPermanent directive

Syntax: RedirectPermanent url-path url
Context: server config, virtual host, directory, .htaccess
Override: FileInfo
Status: Base
Module: mod_alias
Compatibility: This directive is only available in Apache 1.2 and later

This directive makes the client know that the Redirect is permanent (status 301). Exactly equivalent to `Redirect permanent`.

## ScriptAlias directive

Syntax: ScriptAlias url-path directory-filename
Context: server config, virtual host
Status: Base
Module: mod_alias

The ScriptAlias directive has the same behavior as the Alias directive, except that in addition it marks the target directory as containing CGI scripts. URLs with a (%-decoded) path beginning with url-path will be mapped to scripts beginning with directory-filename.

Example:

> `ScriptAlias /cgi-bin/ /web/cgi-bin/`

A request for http://myserver/cgi-bin/foo would cause the server to run the script /web/cgi-bin/foo.

## ScriptAliasMatch

Syntax: ScriptAliasMatch regex directory-filename
Context: server config, virtual host
Status: Base
Module: mod_alias
Compatibility: Available in Apache 1.3 and later

This directive is equivalent to ScriptAlias, but makes use of standard regular expressions, instead of simple prefix matching. The supplied regular expression is matched against the URL, 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 `/cgi-bin`, one might use:

        ScriptAliasMatch ^/cgi-bin(.*) /usr/local/apache/cgi-bin$1

### Apache HTTP Server Version 1.3