"I am webby and I think webby" - AjiNIMC aka Aji Issac Mathew - "I thought and I wrote".

 AjiNIMC logo - Aji Issac Mathew I am Aji Issac Mathew also known as AjiNIMC at various forums. I am webby and I think webby, being a part time blogger, this blog is a documentation of my experiences and my learning.
Blog Stats (06 June 2008): There are currently 306 posts and 1100 comments (and 397,307 spam comments), contained within 17 categories.		RSS for Aji Issac Mathew's blog 
  I am into professional Web Marketing services which includes Web marketing strategies, SEO/SEM, Content Designing, Web Designing for usability, conversion improvement and various other things. There are limited availability per month. We don't take too many clients but we make sure that all our clients get their share of success. I worked on in-house sites for over 5 years, now is the time to help others with my experience. I have a great team helping me achieve this. A very creative and experienced team. I write at http://www.dawebmarketing.com/kb/clients/. Contact aji.issac (at the rate) digitalavenues.com and get your share of success.  

 Home >

HtAccess difficult problems #1

Sep
16

I have spent months working with htaccess doing almost everything possible with it, like checking cookie variable, non-www Domain redirection to www (easy), www subdomain redirection to non-www subdomain (a little tough) e.t.c. The best part of the programming was that we had one htaccess for as many as five sites (plus its alpha, beta sites) and it worked fine with all the regular expressions (everything was variable including the domain name).

Some of difficult problems we faced with htaccess,
Problem 1: Comparison of variables

Solution 1:

According to JDMorgan of webmasterworld.com

There is no ‘native’ support in Apache for comparing two variables, although some operating systems support ‘atomic back-referencess’ which can be used to emulate a compare. This depends on the regex library bundled with the OS> Specifically, POSIX 1003.2 atomic back-references can be used to do a compare by using the fact that if A+A = A+B, then A=B.

RewriteCond %{HTTP_REFERER} ^(http://[^/]+)
RewriteCond %{HTTP_HOST)<>%1 ^([^<]+)<>\1$ [NC]
RewriteRule ^uploads/[^.]+\..{3,4}$ - [L]

Note that the “<>” string is entirely arbitrary and has no special meaning to regular-expressions; It is used here only to demarcate the boundary between the two concatenated variables. The actual ‘compare’ is done in the second RewriteCond, using the atomic back-reference “\1″ to ‘copy’ the value of the string matching the parenthesized pattern directly to its left.

Therefore
if %{HTTP_HOST}<>%{HTTP_REFERER}(partial) == %{HTTP_HOST}<>%{HTTP_HOST}<>%,
then %{HTTP_REFERER}(partial) == %{HTTP_HOST}

This may need some tweaking to fit your actual referrers, since the match between hostname and the partial referrer substring saved in %1 must be exact. And as noted, it will only work on servers which support POSIX 1003.2 regular expressions (FreeBSD is one, and there are others.) I know of no way to support variable-to-variable compares in mod_rewrite without this POSIX 1003.2 trick.

Solution 2:

Set the variable first
SetEnvIfNoCase Referer>http://([a-zA-Z]{2,3})\.idealwebtools\.com\.* HostNameAndReferrerNameAreFromSameDomain=True

And then use it in the logic
RewriteCond %{ENV:HostNameAndReferrerNameAreFromSameDomain} !^True$ [NC]
RewriteRule (.*) redirection [R=301,L]

This post was written by AjiNIMC aka Web Kotler at 10:01 am under category Tech Talks(



3 Comments »

  1. Link to more .htaccess files http://www.acomputerportal.com/htaccess.html

    Link to more Apache open-source software and Apache Servers. Mod Rewrite. http://www.acomputerportal.com/apache.html



    Billy on September 19, 2006 - 8:02 pm @ 8:02 pm

  2. Thanks Billy, for the collection. You can also the check the log file configuration post.



    AjiNIMC on September 19, 2006 - 8:31 pm @ 8:31 pm

  3. Windows Rewrites http://www.acomputerportal.com/windows_rewrites.html



    Windows Rewrites on September 22, 2006 - 6:48 pm @ 6:48 pm

RSS feed for comments on this post · TrackBack URI

Share your thoughts

You are visitor number