Apache Module mod_setenvif

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Description:	Allows the setting of environment variables based -on characteristics of the request
Status:	Base
Module Identifier:	setenvif_module
Source File:	mod_setenvif.c

Summary

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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.

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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.

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- BrowserMatch ^Mozilla netscape - BrowserMatch MSIE !netscape -

BrowserMatch Directive

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Description:	Sets environment variables conditional on HTTP User-Agent -
Syntax:	`BrowserMatch regex [!]env-variable[=value] -[[!]env-variable[=value]] ...`
Context:	server config, virtual host, directory, .htaccess
Override:	FileInfo
Status:	Base
Module:	mod_setenvif

The BrowserMatch is a special cases of the - SetEnvIf directive that - sets environment variables conditional on the - User-Agent HTTP request header. The following two - lines have the same effect:

- BrowserMatchNoCase Robot is_a_robot - SetEnvIfNoCase User-Agent Robot is_a_robot -

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Some additional examples:

- BrowserMatch ^Mozilla forms jpeg=yes browser=netscape - BrowserMatch "^Mozilla/[2-3]" tables agif frames javascript - BrowserMatch MSIE !javascript -

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BrowserMatchNoCase Directive

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Description:	Sets environment variables conditional on User-Agent without -respect to case
Syntax:	`BrowserMatchNoCase regex [!]env-variable[=value] - [[!]env-variable[=value]] ...`
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)

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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 -

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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 -

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SetEnvIf Directive

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Description:	Sets environment variables based on attributes of the request -
Syntax:	`SetEnvIf attribute - regex [!]env-variable[=value] - [[!]env-variable[=value]] ...`
Context:	server config, virtual host, directory, .htaccess
Override:	FileInfo
Status:	Base
Module:	mod_setenvif

The SetEnvIf directive defines - environment variables based on attributes of the request. The - attribute specified in the first argument can be one of three - things:

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An HTTP request header field (see RFC2616 - for more information about these); for example: Host, - User-Agent, Referer, and - Accept-Language. A regular expression may be - used to specify a set of request headers.
One of the following aspects of the request: -
- Remote_Host - the hostname (if available) of - the client making the request
- Remote_Addr - the IP address of the client - making the request
- Server_Addr - the IP address of the server - on which the request was received (only with versions later - than 2.0.43)
- 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 resource requested on the HTTP - request line -- generally the portion of the URL - following the scheme and host portion without the query string. See - the RewriteCond - directive of mod_rewrite for extra information on - how to match your query string.
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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. -Environment variables will be considered only if there was no match -among request characteristics and a regular expression was not -used for the attribute.

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The second argument (regex) is a Perl compatible regular expression. -This is similar to a POSIX.2 egrep-style regular expression. -If the regex matches against the attribute, -then the remainder of the arguments are evaluated.

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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

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varname, or
!varname, or
varname=value

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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 literal value given by - value. Since version 2.0.51 Apache will - recognize occurrences of $1..$9 within - value and replace them by parenthesized subexpressions - of regex.

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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 - : - SetEnvIf ^TS* ^[a-z].* HAVE_TS -

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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.

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The last example will set environment variable - HAVE_TS if the request contains any headers that - begin with "TS" whose values begins with any character in the - set [a-z].

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SetEnvIfNoCase Directive