#!/bin/sh
begin=$(date +%s)
while true; do
 now=$(date +%s)
 diff=$(($now - $begin))
 mins=$(($diff / 60))
 secs=$(($diff % 60))
 echo "vergangene Zeit: $mins:$(printf %02d $secs) \tDrücke\tStrg + C zum Abbrechen\r"
 sleep 1
done