Apache: scope for environmental variables

apache-2.2environment-variablesrewrite

While there's documentation available on Apache environmental variables, I can not find answer to one important question. Imagine I use rewrite rules to set environmental variable

RewriteRule ... ... [E=something:1]

What is the scope of "something" – global Apache server (this means "something" will be available for other request transactions), this request (means that "something" is only valid for THIS http request (and its related processing – but what's about internal redirects and other internal stuff – are they considered as THIS request, or another one?), and may be set differently within another (concurrent) request?

Best Answer

The scope is this request and can be set differently in another concurrent request. The relevant part of the docs is this:

Conditional Per-Request Settings

For additional flexibility, the directives provided by mod_setenvif allow environment variables to be set on a per-request basis, conditional on characteristics of particular requests. For example, a variable could be set only when a specific browser (User-Agent) is making a request, or only when a specific Referer [sic] header is found. Even more flexibility is available through the mod_rewrite's RewriteRule which uses the [E=...] option to set environment variables.

source

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Apache mod_rewrite, using current URL in RewriteCond

You can access the "current" URI via a backreference. From the RewriteRule documentation...

TestString is a string which can contain the following expanded constructs in addition to plain text:

RewriteRule backreferences: These are backreferences of the form $N (0 <= N <= 9), which provide access to the grouped parts (in parentheses) of the pattern, from the RewriteRule which is subject to the current set of RewriteCond conditions.

You can handle the initial slash more cleanly too — the request URI always starts with a /. (The shortest request you can make is GET / HTTP/1.0.) The solution is...

# Map '/' to '/home'
RewriteRule ^/$ /home

# Check for cached page
RewriteCond %{DOCUMENT_ROOT}/system/cache/$1.html -f
RewriteRule ^/(.+)$ /system/cache/$1.html [QSA,L]

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You could write a shell script to set the variable and then run wine.

Best Answer

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