get_line_no

#!/usr/bin/perl -w

# Convert a file offset into a line number

use strict;
use warnings;

if (!@ARGV)
{
	print qq{Usage: $0 file offset
Prints the line number of the given offset in the file.
};
	exit 0;
}

my $file = $ARGV[0];
my $num = $ARGV[1];

open(IN, $file) or die "Cannot open $file: $!";

my $ofs = 0;
while (<>)
{
	my $len = length($_);
	if ($ofs + $len > $num)
	{
		printf "%d:%d\n", $., $num - $ofs;
		exit 0;
	}
	$ofs += $len;
}

close(IN);

print STDERR "Offset is past the end of the file\n";
exit 1;