#!/usr/bin/perl
##################################################
#
# Script:   ntail.pl
# Purpose:  imitate the unix 'tail -f'
# Version:  0.1
# Date:     5/05/2008
#
# nocopyright (:=X  2008  neuzd, neuzd.org
#
##################################################
use strict;
use warnings;
use Time::HiRes qw(usleep);

#The only argument needed is the file to be displayed
my $f;
die "Specify a file\nUSE: ntail.pl <filename>\n" unless @ARGV>0;
$f=$ARGV[0];

my $lines = 10;
open(my $in, "<", $f) or die "Can't open $f: $!";
my @uarr = <$in>;
my @tenlines  = @uarr[$#uarr-$lines .. $#uarr ];

print "$_" foreach @tenlines;

while (<>)
{
    #check every 1 second
    usleep(1000000);
    open(my $due, "<", "$f") or die "Can't open $f: $!";
    my @darr = <$due>;

    unless(@uarr == @darr)
    {
        my $diff = @darr - @uarr;
        my @lastlines = @darr[$#darr-$diff .. $#darr];
        print @lastlines;
        open(my $in, "<", "$f") or die "Can't open $f: $!";
        @uarr = <$in>;
    }
}