#!/usr/bin/perl

## PerlTail
## Does a "tail" of a file using seek.

use strict;

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

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

my $charsperline = shift || 80; ## A rough guess

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+1;

## Figure out how big it is
my $filesize = -s $bigfile;

## We do not want to go back *too* far:
$gobackchars = $filesize if $gobackchars > $filesize;

seek(BIG,-$gobackchars,2);

## We probably arrived in the middle of a line,
## so throw out everything to the start of a new line
<BIG>;

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

close(BIG);