in reply to Re^2: Regular Expression - pattern matching
in thread Regular Expression - pattern matching

#. check the number of characters before the first "_" (underscore). #. If it's return only two characters, then get the string untill it reach the second "_"(underscore)
Okay, well because you are looking for anything that is not an underscore, then a negated character class is probably the way to go. Something like this: 
    if (/^([^_]{2}_[^_]+)_/) {
        print $1;
    }

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else if more than 2 characters then it must be a targetted pattern
Sorry, but I don't get that. What is a "targetted pattern"?

I guess i can't able to use the "\w" (word) pattern, because it will take the whole string as a word.
Yes and no. It's okay, because you are limiting it to only the first two characters with {2}. But it's probably not okay because \w will also match an underscore. So \w{2} would match something like "_a", which I'm pretty sure you don't want.

Cheers,
Darren :)

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Re^4: Regular Expression - pattern matching
by kulls (Hermit) on Feb 22, 2006 at 12:44 UTC
    Hi Darren,
    I'm looking for the pattern like "xxxxx" if it's "xxxx_sssss" and also if it's "xx_ssss" then i need "xx_ssss" .
    I have reuse your code 
     if (/^([^_]{2}_[^_]+)_/) {
        print $1;
    }

    [download]
    and it looks like 
    for(@str) {
             my $temp;
             if (/^([^_]{2}_[^_]+)_/) {
               $temp=$1;
               print $temp."\n";  
         } else {
           ($temp)=$_=~/^([a-z0-9]+)\_/xi;
           print $temp."\n"; 
        }
  }

    [download]

    Unfortunately i didn't get the exact pattern which i showed in my output earlier.
    Can you please correct me if i'm wrong ??
    Thank you in advance.
    -kulls
[reply]
[d/l]
[select]
      Okay, after scratching my head for about 20 minutes, I think I've worked out what you want.

      • If the first two characters are not underscores, but the third character is - then keep everything up to (but not including) the second underscore. Otherwise...
      • Keep everything up to (but not including) the first underscore.
      Is that correct?
      If yes, then the following should do it: 
      for (@strings) {
    my $temp = "";
    if (($temp) = $_ =~ m/^([^_]{2}_[^_]+)_?/) {
        print $temp;
    }
    elsif (($temp) = $_ =~ m/^([^_]+)/) {
        print $temp;
    }
}

      [download]
      Update: Oh, one thing I forgot to point out, was that there was an error in the code in my earlier reply. I hadn't accounted for the fact that there may not be any underscores at all. That's been fixed in the above snippet.
[reply]
[d/l]

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