[SOLVED]Linux schedule 3s

#11:27 13/07/2015
#crontab -e
#Running per 1 mins:
* * * * *  /opt/script/dostuff.sh


#cat /opt/script/dostuff.sh
#dostuff.sh
SCRIPT_RUNNING=/opt/script/process-kill-url
(sleep 3 &&  $SCRIPT_RUNNING) &
(sleep 6 &&  $SCRIPT_RUNNING) &
(sleep 9 &&  $SCRIPT_RUNNING) &
(sleep 12 && $SCRIPT_RUNNING) &
(sleep 15 && $SCRIPT_RUNNING) &
(sleep 18 && $SCRIPT_RUNNING) &
(sleep 21 && $SCRIPT_RUNNING) &
(sleep 24 && $SCRIPT_RUNNING) &
(sleep 27 && $SCRIPT_RUNNING) &
(sleep 30 && $SCRIPT_RUNNING) &
(sleep 33 && $SCRIPT_RUNNING) &
(sleep 36 && $SCRIPT_RUNNING) &
(sleep 39 && $SCRIPT_RUNNING) &
(sleep 42 && $SCRIPT_RUNNING) &
(sleep 45 && $SCRIPT_RUNNING) &
(sleep 48 && $SCRIPT_RUNNING) &
(sleep 51 && $SCRIPT_RUNNING) &
(sleep 54 && $SCRIPT_RUNNING) &
(sleep 57 && $SCRIPT_RUNNING) &
(sleep 60 && $SCRIPT_RUNNING) &