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Full Discussion: if match found go to a particular line in perl
Top Forums Shell Programming and Scripting if match found go to a particular line in perl Post 302180152 by era on Sunday 30th of March 2008 06:10:51 AM
Old 03-30-2008
Don't depend on me, I need to be going back to my day job soon.

There's a number of ways to do this, obviously. The old-fashioned variant would be to remember the previous line and print that when you see the terminator. The really brute Perl approach would be to slurp the whole file and substitute everything with an empty string except the line before the terminator. There's one in the Perl FAQ about that; perlfaq6 and scroll around for related questions. (The question about C comments further down the page has some hints, too.)

But the "previous line" solution is absolutely the simplest in this case, if you have no further requirements.

Code:
perl -ne 'BEGIN { $matching = 0; }
  $matching = 1 if (m/^\*Main Start/);
  next unless $matching;
  print $prev if (defined $prev && m/^\*Main End/);
  $prev = $_'

Not sure about the flow control you tried to describe. Are you supposed to remember everything from main start until main end and print that after the output from the last line before main end? (I guess this already qualifies as a pseudo-code implementation of what it takes. But then maybe I would consider a regex substitution over the whole file, or each *Main Start section, after all.)
Last edited by era; 03-30-2008 at 07:22 AM.. Reason: Add a Perl snippet for remembering previous line
 

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LEARN ABOUT DEBIAN

ppix::regexp::structure::main

PPIx::Regexp::Structure::Main(3pm)			User Contributed Perl Documentation			PPIx::Regexp::Structure::Main(3pm)

NAME

       PPIx::Regexp::Structure::Main - Represent a regular expression proper, or a substitution

SYNOPSIS

	use PPIx::Regexp::Dumper;
	PPIx::Regexp::Dumper->new( 'qr{foo}smx' )
	    ->print();

INHERITANCE

       "PPIx::Regexp::Structure::Main" is a PPIx::Regexp::Structure.

       "PPIx::Regexp::Structure::Main" is the parent of PPIx::Regexp::Structure::Regexp and PPIx::Regexp::Structure::Replacement.

DESCRIPTION

       This abstract class represents one of the top-level structures in the expression. Both PPIx::Regexp::Structure::Regexp and
       PPIx::Regexp::Structure::Replacement are derived from it.

METHODS

       This class provides the following public methods. Methods not documented here are private, and unsupported in the sense that the author
       reserves the right to change or remove them without notice.

   delimiters
       This method returns a string representing the delimiters of a regular expression or substitution string. In the case of something like
       "s/foo/bar/", it will return '//' for both the regular expression and the replacement.

   interpolates
       This method returns true if the regular expression or replacement interpolates, and false otherwise. All it really does is to check whether
       the ending delimiter is a single quote.

SUPPORT

       Support is by the author. Please file bug reports at <http://rt.cpan.org>, or in electronic mail to the author.

AUTHOR

       Thomas R. Wyant, III wyant at cpan dot org

COPYRIGHT AND LICENSE

       Copyright (C) 2009-2012 by Thomas R. Wyant, III

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl 5.10.0. For more details, see the full
       text of the licenses in the directory LICENSES.

       This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of
       merchantability or fitness for a particular purpose.

perl v5.14.2							    2012-06-06					PPIx::Regexp::Structure::Main(3pm)
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