root@isau02:/data/tmp/testfeld> ./loop.ksh
exit code: 0
script name: ./loop.ksh
The process ./loop.ksh is already running. Aborting the current instance of the job ./loop.ksh
root@isau02:/data/tmp/testfeld> ps -ef| grep -i loo
root     29647 32139  0 09:25 pts/0    00:00:00 /usr/bin/ksh ./loop.ksh
root     29685 29659  0 09:26 pts/1    00:00:00 grep -i loo


root@isau02.debeka.de:/data/tmp/testfeld> cat loo*
#!/usr/bin/ksh

typeset -i A=0
SCRIPT_NAME=$0

if [ `ps -ef | grep " ${SCRIPT_NAME}" | grep -v "grep" | wc -l` -gt 1 ]; then
        echo "exit code: $?"
        echo "script name: ${SCRIPT_NAME}"
        echo "The process $0 is already running. Aborting the current instance of the job $0"
        exit 1
fi

while (( $A != 1 )); do
        sleep 1
done

exit 0