Shell Programming and Scripting

 
[[ -f /tmp/tool.sh.lock ]] && exit 1
> /tmp/tool.sh.lock
.....
rm /tmp/tool.sh.lock
exit

value=""
ps -ef | grep 'tool.sh' | grep -v 'grep' | read value
[[ ! -z $value ]] && exit 1

#!/bin/ksh

FUSER='/usr/sbin/fuser'
  while :
  do
     myPID="$$"
     echo "My pid->[${myPID}]"
     FUSERout=$(${FUSER} $0 2>/dev/null)
     echo "fuser ->[${FUSERout}]"
     numProc=$(echo "${FUSERout}" | nawk '{print NF}')
     if [ "${numProc}" -gt 1 ]; then
        echo "[$0]: is ALREADY running"
     else
        echo "[$0] is NOT running"
     fi

     sleep 5
     echo "---"
  done

pidof -x -o $$ $(basename "$0") && exit 1