#!/usr/bin/perl
#        $Id: nist.pl,v 1.2 2004/12/07 15:12:38 cinar Exp $
#
# Nist.pl to keep your system time up to date by using time servers.
# Copyright (C) 1998 - 2002 Ali Onur Cinar <cinar(a)zdo.com>
#
# Y2K fixes by Frank Denis aka Jedi/Sector One <j@4u.net>
# BSD-based OS detection added by Will (dirtymac) <dirtymac@datasync.com>
#
# Latest version can be downloaded from:
#
#   http://www.zdo.com
#   http://briefcase.yahoo.com/cinara  (Downloads folder)
#   http://www.cpan.org (Check for mirror sites)
#   ftp://mirror.hiwaay.net/CPAN/authors/id/A/AO/AOCINAR/nist*
#   ftp://sunsite.unc.edu/pub/Linux/system/admin/timei/nist*
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version. And also
# please DO NOT REMOVE my name, and give me a CREDIT when you use
# whole or a part of this program in an other program.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

use Socket qw(PF_INET SOCK_STREAM AF_INET);
use POSIX qw(mktime);

$timeserver = 'time-A.timefreq.bldrdoc.gov';    # time server
$port = '13';                                   # time port (default:13)
$timediff = '-06:00:00';                        # time differance
$datepr = '/bin/date';                          # full path of date


$timediff =~/(.)(..).(..).(..)/g;
$diff = (($2*3600)+($3*60)+$4);
$diff = "$1$diff";

if ($> ne 0)
{
   print STDERR 
    "This program should run as root user to be able to update sytem date.\n";
   exit;
}

if ($timeserver =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/)
{
   $timeserver_addr = pack('C4', $1, $2, $3, $4);
} else {
   $timeserver_addr = gethostbyname($timeserver);
}

print "Connecting to $timeserver on port $port...\n";

if (!socket(NIST, AF_INET, SOCK_STREAM, getprotobyname("tcp") || 6))
{
  print "socket failed ($!)\n"; exit;;
}

if (!connect(NIST, pack('Sna4x8', AF_INET, $port, $timeserver_addr)))
{
   print "connect to $timeserver failed ($!)\n"; exit;
}

while (<NIST>)
{
   $time_data_raw = $_;
   last if ( /NIST/);
}

close NIST;

$time_data_raw =~ /.{6}(..).(..).(..).(..).(..).(..)/g;
print "Current GMT is $1-$2-$3 $4-$5-$6\n";

&DateToSec($1,$2,$3,$4,$5,$6);
$datsec += $diff;
&SecToDate($datsec);

printf ("Local time is  %02d-%02d-%02d %02d-%02d-%02d\n", $year,
$month, $day, $hour, $min, $sec);
print "Updating the system time. ";

$os = `uname`;
if ($os =~ m/BSD/i) {
  $date_command = sprintf ("$datepr %04d%02d%02d%02d%02d.%02d",$year,
$month, $day, $hour, $min, $sec);
} else {
  $date_command = sprintf ("$datepr %02d%02d%02d%02d%04d.%02d",$month,
$day, $hour,$min, $year, $sec);
}

system ($date_command);
print "Done.\n";

sub DateToSec
{
   $year = @_[0];$month = @_[1];$day = @_[2];
   $hour = @_[3];$min = @_[4];$sec = @_[5];
   $datsec = POSIX::mktime($sec, $min, $hour, $day - 1,
     $month - 1, $year + 100);
}

sub SecToDate
{
   $datsec = @_[0];
   ($sec, $min, $hour, $day, $month, $year, $wday, $yday, $isdst) =
    localtime($datsec);
   $day++;
   $month++;
   $year += 1900;
}