Re: Printing line before matching expression

[uday_sagar]

Hope you would be interested in this!

open (INPUT, $ARGV[0]) or die "I couldn't get at input text";
open (SAME_INPUT, $ARGV[0]) or die "I couldn't get at input text";
open (OUTPUT, '>outfile.txt') or die "Can't write to outfile: $!";

while ($line = <INPUT>) {
if (( $line =~ /index_1/ ) and ($line =~ /6/)) {
$index = $.-2;
}
}

while ($line = <SAME_INPUT>) {
if ($. == $index) {
print OUTPUT $line;
}
}

[Laurent_R]

Although possibly not terribly efficient, I like the idea of using 2 file handlers, it makes the code quite simple. But I would change it to something like this:

open my $INPUT, "<", $ARGV[0] or die "I couldn't get at input text";
open my $SAME_INPUT, "<", $ARGV[0] or die "I couldn't get at input tex
+t";
my $offset = $ARGV[1];

my $line = <$INPUT> for (1..$offset); # discard the n first lines, can
+'t do anything with them anyway
while (<$INPUT>) {
    $line = <$SAME_INPUT>;
    print $line if /$regex/;
}

There is also the alternative of slurping the file into an array and walking through the array. Reading the minus $n line is then trivial.

[uday_sagar]

Yes, concept of offset is good! :-)