#!/bin/sh
hours=`date | cut -c12-13`
minutes=`date | cut -c15-16`
seconds=`date | cut -c18-20`

while true
do
  echo "$hours:$minutes:$seconds"
  sleep 0.99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
  seconds=`expr $seconds + 1`
  seconds=`printf "%02d" $seconds`
  if [ $seconds = 60 ]
  then
    seconds=00
    minutes=`expr $minutes + 1`
    minutes=`printf "%02d" $minutes`
    if [ $minutes = 60 ]
    then
      minutes=00
      hours=`expr $hours + 1`
      hours=`printf "%02d" $hours`
      if [ $hours = 25 ]
      then
        hours=01
      fi
    fi
  fi
done