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From "Joao Andrade" <>
Subject [users@httpd] Regular expressions in URL rewriting
Date Sun, 12 Oct 2003 13:16:50 GMT

    Hi there folks,

    That's my very first message to the list, so excuse me if I do any
rookie mistakes. But I'll tell you, I've been through the FAQ and also read
the list archives. Let me first introduce you to the bigger problem.

    What I wanted to do was nothing fancy, my goal was to implement the
concept of "abstract url" as its defined below from an internet textbook

>abstract URLs
>As an engineer your primary contributions to an Internet service will be
data model and interaction design (Steps 1 through 3). When you're sketching
the page flow for a discussion >forum on a white board you give the pages
names such as "all-topics", "one-topic", "one-thread", "post-reply",
"post-reply-confirm", etc. Let's call these abstract URLs. Suppose that >you
elect to implement your service in Java Server Pages. Does it make sense to
have the URLs be "all-topics.jsp", "one-topic.jsp", "one-thread.jsp", etc.?
Why should the users see >that you've used JSP? Should they care? And if you
change your mind and switch to Perl, will you change the user-visible URLs
to "", "", "", >etc.? This will break
everyone's bookmarks. More importantly, this change will break all of the
links from other sites to yours. That's a high price to pay for an
implementation >change that should have been invisible to end-users.
>You need a Web programming environment powerful enough that you can build
something that we'll call a request processor. This program looks at an
incoming abstract URL, e.g., >"one-topic", and follows the following logic:

  a.. is there a .jsp file in the file system; if so, execute it
  b.. look for headers requesting WML for a WAP device; if so and there is a
.wml file in the file system, serve it, if not, continue
  c.. look for a .html file
  d.. look for a .jpg
  e.. look for a .gif
(You'll want to customize the preference order for your server.)

    Now to the more specific questions:

    1. Will mod rewrite to the above, or after rewriting an URL from to
will it show the client this last one?

    2. If the answer for "1" is yes would mod_alias be better?

    3. I tried some number of regular expressions with rewrite and none of
them have worked, I fear that there's something missing for its proper work.
I tried

        RewriteRule (.*) $1.php (the actual rule would be more complex, this
was only for test)

        and I still got a 404 error for
(hello.php does exist).

    4. I've read this from a message in the list:

        > RedirectMatch .*^/obit.*
        > (i.e. 0 or more any characters then anything but a "/" then "obit"
then 0 or more
        > any characters. This should match "/March.obits.html" but not
match "/obit.php".
        > Check up on regular expressions to refine it...)

        How does the program know it has to stop after inserting a .* at the
begining, doesn't it to get any character, any number of times, wouldn't it
go till the end of the line?

    5.  What's with the '^' and '$' anyway? I've seen this expression in the


        one tells to align at he beginning of a line and the other to align
at the end. What's the sense in of it?

        That's it I hope to have been clear enough. Thanx a lot for your


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