#!/bin/bash

ntp_server="clock.redhat.com"
ntp_prog=`ls -l /etc/init.d/ | awk '{print $NF}' | grep "ntp\|chrony"`
echo "NTP daemon is detected as $ntp_prog"
drift_log="/tmp/drift.log"

error()
  {
    echo "Error: $1"
    exit 1
  }

[[ -n $ntp_prog ]] || error "cannot find ntp daemon"
[[ `which ntpdate` ]] || error "cannot find ntpdate"

[[ -f /var/lock/subsys/ntpd ]] || [[ -f /var/run/ntpd.pid ]] || [[ -f /var/run/chronyd.pid ]] && /etc/init.d/$ntp_prog stop
sleep 3

ntpdate $ntp_server || error "unable to contact NTP server $ntp_server"
/sbin/hwclock

while true
  do
    [[ -f /var/lock/subsys/ntpd ]] || [[ -f /var/run/chronyd.pid ]] && /etc/init.d/$ntp_prog stop > /dev/null
    out=`ntpdate -q $ntp_server | grep ntpdate`
    /etc/init.d/$ntp_prog start > /dev/null
    time=`echo $out | awk '{print $3}'`
    skew=`echo $out | awk '{print $10}' | awk -F. '{print $1}'`
    echo "$time $skew seconds"
    echo "$time $skew seconds" >> $drift_log
    sleep 60
  done