http://www.perlmonks.org?node_id=1042551

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

I have many text files of the same format that I must read. The lines of interest in the text files are between two lines that are consecutive asterisks (************************). What would be an efficient way for me to only consider the lines between these two lines of asterisks?

Replies are listed 'Best First'.
Re: Read Between the Lines
by choroba (Cardinal) on Jul 05, 2013 at 00:21 UTC
    You can use the flip flop operator (see Range Operators): 
    while (<>) {
    if (/^\*+$/ ... /^\*+$/) {
        print "Inside: $_";
    }
}

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    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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[d/l]

      I like it. I think the OP didn't want the asterisks themselves printed, so a small addition would clear that up:

          while (<>) {
         print if /^\*+$/ ... /^\*+$/ and not /^\*+$/;
    }

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[d/l]
Re: Read Between the Lines
by parv (Parson) on Jul 05, 2013 at 00:32 UTC
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[d/l]
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Re: Read Between the Lines
by rjt (Curate) on Jul 05, 2013 at 01:07 UTC

    If your file is small enough (i.e., not many megabytes in size), slurping the whole thing and using a regexp will be efficient enough, and allow you to capture multiple groups, if necessary, without matching unbalanced asterisks.

    $_ = do { local $/; <> };
print "Match: $_" for /^\*+$ (.+?) ^\*+$/smxg;

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    Full example after the <readmore>.

    Read more... (1063 Bytes)
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Re: Read Between the Lines
by sundialsvc4 (Abbot) on Jul 05, 2013 at 01:54 UTC

    A more generalized way to handle such requirements is with a Finite-State Machine (FSM) approach.   The algorithms consider, not only the current line of input, but the $state that the FSM is “in” at the time, where the current value of $state is determined by recent history of lines seen.   It is probably overkill for a requirement as trivial as this one seems to be,.

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