Well, you'll have to store the lines. And it's going to be tricky to correctly handle matches where the context overlaps, ie where one match follows less than 2n lines from the previous.

The easiest thing to do is use the toolbox: egrep -C n c9391b56-b174-441b-921c-7d63 GWSvc.log

Update: the following should work and handle all edge cases:

my @backlog;
my $to_print = 0;
my $context_size = 10;

while(<>) {
    $to_print = 1 + $context_size if /c9391b56-b174-441b-921c-7d63/;
    push @backlog, $_;
    if( $to_print ) {
        print shift @backlog;
        --$to_print;
    }
    elsif( @backlog > $context_size / 2 ) {
        shift @backlog;
    }
}

print shift @backlog while @backlog and $to_print--;

[download]

Makeshifts last the longest.

In reply to Re: grab 'n' lines from a file above and below a /match/ by Aristotle
in thread grab 'n' lines from a file above and below a /match/ by barathbr

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