What does this apache rewrite means?

Question

RewriteCond %{QUERY_STRING}    (.*)\?mem=stats$
RewriteRule  ^/(.*)$           http://X.X.X.X/$1?%1 [P,L]

If the request is /asdf?mem=stats , will it rewrite to /asdf?mem=stats?asdf ?

since $1 is asdf?mem=stats and %1 is asdf ???

Answer 1

The %{QUERY_STRING} variable contains the query string without the leading ? (or anything before it), so %1 will never contain part of the request before query string.

If you enable mod_rewrite logging by adding LogLevel rewrite:trace6 to your VirtualHost configuration, you will see this for your RewriteCond and /asdf?mem=stats request:

... RewriteCond: input='mem=stats' pattern='(.*)\\?mem=stats$' => not-matched

Also, in your RewriteRule , pattern will be matched against the part of the URL after the hostname and port, and before the query string. Therefore $1 will, even on wildcard match, not contain the query string part of the request. You can see that in log as:

... applying pattern '^/(.*)$' to uri '/asdf'