Help with Regex for Apache Error Logs

coolmichael has asked for the wisdom of the Perl Monks concerning the following question:

In the standard apache error log file format, we have:

[Mon Jun 17 23:09:46 2002] [error]usage: tie @array, Tie::File, filena
+me, [option => value]... at d:/httpd/apache/perl/velog.pl line 16

[Mon Jun 17 23:24:44 2002] [error] [client 127.0.0.1]File does not exi
+st: d:/httpd/apache/htdocs/kjh
[download]

I would like to add a <BR> tag after the blocks of [ ] but before the error begins, like this:

[Mon Jun 17 23:09:46 2002] [error]
usage: tie @array, Tie::File, filename, [option => value]... at d:/htt
+pd/apache/perl/velog.pl line 16

[Mon Jun 17 23:24:44 2002] [error] [client 127.0.0.1]
File does not exist: d:/httpd/apache/htdocs/kjh
[download]

My first try was to just go with s/^(\[.*\])/$1<br>/; which worked all too well. . The problem was that it was matching everything up to and including any ]'s in the error string as well. After reading Ovid's writeup(Thank you for Death to Dot Star!), I changed my regex to s/^(\[^]])/$1<br>/;. That change fixed things too much in the other way (only capturing the first [ ]). Now, I've come up with what seems to me to be very complicated.

    s/^               #start of string
      (               #start capture
        (?:           #begin non-capturing repeating
          \[          #literal [
          [^]]*       #anything that isn't a ]
          ]\s*        #ending ] and optional spaces
        )+            #end non capturing repeating
      )               #end capture
      /               #end match
      $1<br>/gx;
[download]

Iwas surprised at myself for coming up with this. I would very much appreciate any suggestions you might have to simplify this beast. Have I missed anything (I'm very good at missing the good points)?

Thank you.

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Re: Help with Regex for Apache Error Logs by greenFox (Vicar) on Jun 18, 2002 at 10:48 UTC
Your specification seemed to say "match [error] followed by zero or more things contained in square brackets" so I was a bit surprised when your re did not contain the string "error" :) Here is a version that looks for "[error]", not sure if it is any better- `s/( # begin capture \[error\] # "error" in square brackets :) \s* # optional whitespace (?: # non capture \[ # literal [ [^\]]+ # 1 or more non "]" \] # literal ] )* # end non capture ) # end capture /$1<br>/x;` [download] -- my $chainsaw = 'Perl';	[reply] [d/l]

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Re: Help with Regex for Apache Error Logs
by greenFox (Vicar) on Jun 18, 2002 at 10:48 UTC

Your specification seemed to say "match [error] followed by zero or more things contained in square brackets" so I was a bit surprised when your re did not contain the string "error" :) Here is a version that looks for "[error]", not sure if it is any better-

    
 s/(            # begin capture
     \[error\]  # "error" in square brackets :)
     \s*        # optional whitespace
     (?:        # non capture
       \[       # literal [
       [^\]]+   # 1 or more non "]"
       \]       # literal ]
      )*        # end non capture 
    )           # end capture
   /$1<br>/x;
[download]

--
my $chainsaw = 'Perl';

[reply]
[d/l]