Listing 1 timeout_countdown

#!/bin/ksh
# timeout_countdown:
# kill the parent process if the user has not entered input within 
# a given time frame.

integer timeout=300
integer pid=0
directory=/tmp

while getopts d:p:t: option
do
   case $option in
      d)
         directory=$OPTARG
         ;;
      p)
         pid=$OPTARG
         ;;
      t)
         timeout=$OPTARG
         ;;
   esac
done

shift $(($OPTIND - 1))
readonly operand=$1

if [[ -z $operand ]]
then
   exit 1
fi

if [[ $pid -eq 0 ]]
then # determine parent process id if none passed
   pid=$(echo $(ps -p $$ -o ppid | tail -1))
fi

timeout_file=$directory/.timeout_countdown.$pid

case $operand in
   start)
         echo $$ > $timeout_file
         sleep $timeout
         rm -f $timeout_file
         kill -15 $pid 2>&- >&-
         ;;
   stop)
         if [[ -f $timeout_file ]]
         then
            pid=$(cat $timeout_file)
            command=$(ps -o args -p $pid | tail -1)

            # 2nd field is the timeout_countdown command
            command=$(echo "$command"|cut -d " " -f2)

            if [[ $(basename $0) == $(basename $command) ]]
            then
               kill -9 $pid 2>&- >&-
               rm -f $timeout_file
            fi
         fi
         ;;
      *)
         exit 1
         ;;
esac

exit 0