Lighttpd's redirect only works with parentheses around the whole regex

Question

I'm using lighttpd 1.4.28

Here is my redirect rule :

$HTTP["host"] =~ "^([^.]+\.[^.]+)$" {
        url.redirect = ( "^/(.*)" => "http://www.%0/$1" )
}

It's supposed to redirect anydomain.anytld to www.anydomain.anytld and it works like a charm like I've written it here (of course, using %1 also works, since it refers to the parentheses.)

Yet, I'm baffled as to why it only works with the pair of parentheses you can see in the trigger regex.

%0 is supposed to catch the whole result, isn't it ? It doesn't even refer to a pair of parenthese, unlike %1, %2, etc. But if I remove those parentheses, like this :

$HTTP["host"] =~ "^[^.]+\.[^.]+$" {
        url.redirect = ( "^/(.*)" => "http://www.%0/$1" )
}

I get this error when trying to restart lighttpd :

unreachable else condition 2012-10-17 11:34:10: (configfile.c.918) source: /etc/lighttpd/lighttpd.conf line: 173 pos: 14 parser failed somehow near here: (EOL)

Thanks !

score 0 · Accepted Answer · answered Oct 17 '12 at 09:45

It's because %0 matches the entire substring or the first expression, which, by definition is the enclosing () set. This would allow you to use a more complicated regex with nested (ie ((()))) parenthesis, and pulling the entirety of it. From what I can understand, that is the construct of Lighttpd's regex parser.

http://redmine.lighttpd.net/projects/1/wiki/Docs_ModRewrite

Lighttpd's redirect only works with parentheses around the whole regex

1 Answers1