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Apache HTTP Server Version 1.3
Module mod_setenvif
This module provides the ability to set environment variables based upon attributes of the
request.
Status:
Base
Source
File: mod_setenvif.c
Module
Identifier: setenvif_module
Compatibility:
Available in Apache 1.3 and later.
Summary
The mod_setenvif module allows you to set environment variables according to
whether different aspects of the request match
regular expressions you specify.
These environment variables can be used by other parts of the server to make decisions about
actions to be taken.
The directives are considered in the order they appear in the configuration files. So more
complex sequences can be used, such as this example, which sets netscape if the
browser is mozilla but not MSIE.
BrowserMatch ^Mozilla netscape
BrowserMatch MSIE !netscape
For additional information, we provide a document on
Environment Variables in Apache.
Directives
Syntax:
BrowserMatch regex env-variable[=value] [env-variable[=value]]
...
Default:
none
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
Compatibility:
Apache 1.2 and above (in Apache 1.2 this directive was found in the now-obsolete mod_browser
module); use in .htaccess files only supported with 1.3.13 and later
The BrowserMatch directive defines environment variables based on the User-Agent
HTTP request header field. The first argument should be a POSIX.2 extended regular expression
(similar to an egrep-style regex). The rest of the arguments give the names of
variables to set, and optionally values to which they should be set. These take the form of
- varname, or
- !varname, or
- varname=value
In the first form, the value will be set to "1". The second will remove the given
variable if already defined, and the third will set the variable to the value given by value.
If a User-Agent string matches more than one entry, they will be merged. Entries
are processed in the order in which they appear, and later entries can override earlier ones.
For example:
BrowserMatch ^Mozilla forms jpeg=yes browser=netscape
BrowserMatch "^Mozilla/[2-3]" tables agif frames javascript
BrowserMatch MSIE !javascript
Note that the regular expression string is case-sensitive. For case-INsensitive
matching, see the BrowserMatchNoCase directive.
The BrowserMatch and BrowserMatchNoCase directives are special
cases of the SetEnvIf and
SetEnvIfNoCase
directives. The following two lines have the same effect:
BrowserMatchNoCase Robot is_a_robot
SetEnvIfNoCase User-Agent Robot is_a_robot
Syntax:
BrowserMatchNoCase regex env-variable[=value] [env-variable[=value]]
...
Default:
none
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
Compatibility:
Apache 1.2 and above (in Apache 1.2 this directive was found in the now-obsolete mod_browser
module)
The BrowserMatchNoCase directive is semantically identical to the
BrowserMatch directive. However, it provides for
case-insensitive matching. For example:
BrowserMatchNoCase mac platform=macintosh
BrowserMatchNoCase win platform=windows
The BrowserMatch and BrowserMatchNoCase directives are special
cases of the SetEnvIf and
SetEnvIfNoCase
directives. The following two lines have the same effect:
BrowserMatchNoCase Robot is_a_robot
SetEnvIfNoCase User-Agent Robot is_a_robot
Syntax:
SetEnvIf attribute regex env-variable[=value] [env-variable[=value]]
...
Default:
none
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
Compatibility:
Apache 1.3 and above; the Request_Protocol keyword and environment-variable matching are only
available with 1.3.7 and later; use in .htaccess files only supported with 1.3.13 and later
The SetEnvIf directive defines environment variables based on attributes of
the request. These attributes can be the values of various HTTP request header fields (see
RFC2616 for more information about
these), or of other aspects of the request, including the following:
- Remote_Host - the hostname (if available) of the client making the request
- Remote_Addr - the IP address of the client making the request
- Remote_User - the authenticated username (if available)
- Request_Method - the name of the method being used (GET, POST,
et cetera)
- Request_Protocol - the name and version of the protocol with which the
request was made (e.g., "HTTP/0.9", "HTTP/1.1", etc.)
- Request_URI - the portion of the URL following the scheme and host portion
Some of the more commonly used request header field names include Host, User-Agent,
and Referer.
If the attribute name doesn't match any of the special keywords, nor any of the
request's header field names, it is tested as the name of an environment variable in the list
of those associated with the request. This allows SetEnvIf directives to test
against the result of prior matches.
Only those environment variables defined by earlier SetEnvIf[NoCase]
directives are available for testing in this manner. 'Earlier' means that they were defined
at a broader scope (such as server-wide) or previously in the current directive's scope.
Example:
SetEnvIf Request_URI "\.gif$" object_is_image=gif
SetEnvIf Request_URI "\.jpg$" object_is_image=jpg
SetEnvIf Request_URI "\.xbm$" object_is_image=xbm
:
SetEnvIf Referer www\.mydomain\.com intra_site_referral
:
SetEnvIf object_is_image xbm XBIT_PROCESSING=1
The first three will set the environment variable object_is_image if the
request was for an image file, and the fourth sets intra_site_referral if the
referring page was somewhere on the www.mydomain.com Web site.
Syntax:
SetEnvIfNoCase attribute regex env-variable[=value] [env-variable[=value]]
...
Default:
none
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
Compatibility:
Apache 1.3 and above; the Request_Protocol keyword and environment-variable matching are only
available with 1.3.7 and later; use in .htaccess files only supported with 1.3.13 and later
The SetEnvIfNoCase is semantically identical to the
SetEnvIf
directive, and differs only in that the regular expression matching is performed in a
case-insensitive manner. For example:
SetEnvIfNoCase Host Apache\.Org site=apache
This will cause the site environment variable to be set to "apache"
if the HTTP request header field Host: was included and contained Apache.Org,
apache.org, or any other combination.
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