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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 OSF1

prev

prev(1) 						      General Commands Manual							   prev(1)

NAME

       prev - show the previous message (only available within the message handling system, mh)

SYNOPSIS

       prev [+folder] [-[no]header] [-help] [-showproc program] [-noshowproc] [options to showproc]

OPTIONS

       Displays  a  one-line  header before the message. The header consists of the name of the folder and the message number. This is the default
       behavior. It can be suppressed with the -noheader option.  Prints a list of the valid options to this command.	Specifies  an  alternative
       program	to list messages. The default is to use the program defined by the showproc: entry in the file. As with show, you can give options
       to the showproc program at the command line. These are passed directly to showproc by prev.

       The defaults for this command are:

       +folder defaults to the current folder -header

DESCRIPTION

       The prev command displays the previous message in the current folder.  The previous message is the one before the current  message  in  the
       folder.	The message that is shown becomes the current message.

       You  can  specify  a  folder other than the current folder by using the +folder argument. If you specify a folder, that becomes the current
       folder.

RESTRICTIONS

       The prev command is really a link to the show program. As a result, if you make a link to prev and that link is not called prev, your  link
       will act like show instead. To avoid this, add a profile-entry for the link to your MH profile and add the argument prev to the entry.

PROFILE COMPONENTS

       Path: To determine your Mail directory

       showproc: Program to show the message

EXAMPLES

       The command in the following example displays the previous message in the folder +copylog: $ prev +copylog

FILES

       The user profile.

SEE ALSO

       show(1), next(1)

																	   prev(1)
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