Hi all,

I am trying to match a specific part of a line and print the line above and below it, in full.

Through various internet searches I have found this code which I believe is suitable to the task: 
use strict;
use warnings;

open( my $fh, '<', 'input.txt') or die "Error opening file - $!\n";
open OUT, ">", "output.txt" or die "could not open output.txt $! \n";

my $this_line = "";
my $do_next = 0;

while(<$fh>) {
    my $last_line = $this_line;
    $this_line = $_;

    if ($this_line =~ /<DATA>/) {
        print OUT $last_line unless $do_next;
        print OUT $this_line;
        $do_next = 1;
    } else {
        print OUT $this_line if $do_next;
        $last_line = "";
        $do_next = 0;
    }
}
close ($fh);

__DATA__
4386_7#8
4350_7#6
4414_1#6
4465_5#1
etc...

[download]

The data are not a line by themselves, rather they are part of a line.

When I run this code the output produced is just a blank text file. It does not return any error messages, and I am sure that matches I am searching for are in the file I am searching.

Any help as to what might be the problem would be much appreciated.

Thanks in advance,

Bio

In reply to How to print the lines immediately above and below a matching line? by Bio90

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