#!/usr/bin/perl

use strict;

my $bigfile = shift or die "Usage: $0 filename <lines>\n";

my $charsperline = 80; ## A rough guess, adjust as needed

my $linesback = shift || 10; ## How many "lines" back to read

open(BIG, $bigfile) or die "Could not open $bigfile: $!\n";

## Make a reasonable guess as to how far back to go.
my $gobackchars = $linesback*$charsperline;

## Figure out how big it is, so we don't go *too* dar back:
my $filesize = -s $bigfile;
$gobackchars = $filesize if $gobackchars > $filesize;

## Go to the end of the file minus that many characters
seek(BIG,-$gobackchars,2);

## We probably arrived in the middle of a line,
## so throw out everything until the start of a new line
## (As determined by $/)
<BIG>;

## Now we print out the rest of the lines:
print while(<BIG>);

close(BIG);