Programming Forums - Problem with regular expression?

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Problem with regular expression?

I'm trying to write a program that processes a web log file. Here's an antry example:

3236 "GET /robert/./index.php?page=links HTTP/1.1" "30/Sep/2005:11:11:38 -0400" "Java/1.4.1_05" "-" - - 200 69.177.179.241

I made a regex to get the important parts and trying to print out the first reference for the 'bytes':

$entry =~ /\

                   (\d+)\s+                        #bytes

                   (".*")\s+               #method.url.hvers

                   (".*")\s+               #date & time

                   (".*")\s+               #useragent

                   (".*")\s+               #referer

                   .*\s+.*\s+

                   (\d+)\s+                #statuscode

                   (.*)                    #ipaddy

                   /x;

             $bytes = $1;

             print $bytes;

I get an error

Use of uninitialized value in print at ./prog11.pl line 54 (#1)

    (W uninitialized) An undefined value was used as if it were already

    defined.  It was interpreted as a "" or a 0, but maybe it was a mistake.

    To suppress this warning assign a defined value to your variables.

when I try to print it out. Is there something wrong with the expression? The way I see it, it should work

What line is line 54?

Sorry, forgot to post that. It's the 'print $bytes'. It works until I put the print statement in there.

That regexp looks a little strange to me. To quote the sense of it here, but in the squished up way I'm more used to looking at:

(\d+)\s+(".*")\s+(".*")\s+(".*")\s+(".*")\s+.*\s+.*\s+(\d+)\s+(.*)

This regexp seems to have several faults. The first one is (".*") to match a quoted string - what this actually matches is zero or more of anything (including quotes) surrounded by quotes. You could use a nongreedy quantifier here (? after the *), but the more efficient method would be to change that . to a character class that, if you wanted to be generous, just excluded quotes:

^(\d+)\s+("[^"]+")\s+("[^"]+")\s+("[^"]+")\s+("[^"]+")\s+\S+\s+\S+\s+(\d{3})\s+(.*)$

I haven't actually tested the above expression. I've replaced (".*") with the version with the character class each time it occurs, and replaced the two .*'s later (that you weren't capturing) with \S (nonwhitespace) because otherwise the .* consumes the whitespace too. I changed the \d+ for the status code with \d{3} (the {3} is a quantifier meaning exactly three of the preceding atom, which is OK here since all HTTP status codes are 3 digits long). Other than that, I've added start and end anchors (^ and $) to the expression to make sure it matches the whole thing and fails to match on lines it can't do that on.

Like I say, I haven't actually tested this, but I hope it helps. This may not appear to have much to do with the error about $bytes - but if the first .* construct ends up eating all the text, it prevents the expression matching, and if the whole expression doesn't match, none of the submatch variables will be set.

Hope this helps!