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Re^3: Perl RE; how to capture, and replace based on a block?

by Laurent_R (Abbot)
on Dec 18, 2013 at 07:46 UTC ( #1067604=note: print w/replies, xml ) Need Help??


in reply to Re^2: Perl RE; how to capture, and replace based on a block?
in thread Perl RE; how to capture, and replace based on a block?

By default, Perl RE are greedy. Have you considered the possibility that the end of line might be more than \n (if the file is coming from Windows, for example)?
  • Comment on Re^3: Perl RE; how to capture, and replace based on a block?

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Re^4: Perl RE; how to capture, and replace based on a block?
by taint (Chaplain) on Dec 18, 2013 at 08:02 UTC
    Greetings, Laurent_R, and thanks for the reply.

    Oh yes. I'm keen on the \n v \r v \n\r thing, and you're absolutely correct. Except, in my case, I'm on a *NIX box, and I've written the files myself. So I know they're utf-8 (no BOM), with newlines, no "hard" returns. :)

    Maybe it's just the examples I was reading (perlrequick, perlretut, and perlfaq6) but I got the impression that Perl RE wasn't greedy. More Perl RE reading, I guess.

    Thanks again, for the response Laurent_R.

    --Chris

    Yes. What say about me, is true.
    

      Hi Chris

      just a quick example on greedy and non greedy quantifiers, under the Perl debugger:

      DB<1> $string = "foo bar foo bar foo"; DB<2> x $string =~ /(fo.*ar)/ 0 'foo bar foo bar' DB<3> x $string =~ /(fo.*?ar)/ 0 'foo bar' DB<4>
      As you can see the default "*" quantifier is greedy, so that the regex tries to match as much as possible. Using the modified "*?" quantifier, the regex becomes non greedy. You will see the same type of result if you try the "+" and the "+?" quantifiers.

        Thanks Laurent_R for the help.

        Your example helps better explain why I got the impression Perl was not greedy, the way sed is. Most all the examples I read in the perldocs, used .*?. But my experiments, and re-training myself with Perl RE's. Seems to show, once I get out of the sed habits. Perl will be a lot more flexible, and powerful. I should have started this a l-o-o-n-g time ago. :P

        Thanks again, Laurent_R. I really appreciate it.

        --Chris

        Yes. What say about me, is true.
        

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