in reply to Print Lines above and below string

So you want the context of the matched string. You will need to keep a rolling window of the last few lines you've seen. Actually, if your input isn't huge, just slurp up into an array, like so (untested):

open LOGFILE, "<$file";
@lines = <LOGFILE>;
for my $i (0..$#lines) {
  next unless $lines[$i] =~ /$string_to_find/i;
  my $a = $i - 5 < 0 ? 0 : $i - 5;;
  my $b = $i + 5 > $#lines ? $#lines : $i + 5;
  print $lines[$_i] for my $_i ($a..$b);
}

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Re^2: Print Lines above and below string
by coding_new (Sexton) on Aug 10, 2011 at 15:39 UTC

    Thanks for the input. Few questions. My file sizes will be around 2.5 megs max. Not sure if that's a problem or not. Also once I ran the script you provided, I got an error on the last line

    Here is the error: syntax error at ./readlog5.pl line 12, near "$_i ("

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Re^2: Print Lines above and below string
by ww (Archbishop) on Aug 10, 2011 at 22:19 UTC

    ++ for "Close!" ...but "untested" lets typos slip by:

    open (LOGFILE, "<$file") or die "Can't open $file";
my @lines = <LOGFILE>;
my $lines; my $i;
for $i(0..$#lines) {
    next unless $lines[$i] =~ /$string_to_find/i;
      my $a = $i - 5 < 0 ? 0 : $i - 5;;
    my $b = $i + 5 > $#lines ? $#lines : $i + 5;
    for $i($a..$b) {
        print $lines[$i];
    }
}

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Re^2: Print Lines above and below string
by Anonymous Monk on Mar 24, 2016 at 09:12 UTC
    what $#lines does? would anyone please me
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