Shell Programming and Scripting

#!/bin/ksh
 
set -o monitor # must set to invoke CHLD signals
 
typeset -i TOTAL_PROC
function do_child
{
echo "ENTER CHILD $PPID with total  $TOTAL_PROC"
sleep 5
echo "Exit CHILD $PPID total $TOTAL_PROC "
exit 0
}
 
function child_exit_handler
{
echo "Enter child handler total $TOTAL_PROC "
(( TOTAL_PROC  -=  1 ))
echo "Exit child handler total $TOTAL_PROC "
}
 
TOTAL_PROC=0
 
LOOP_COUNT=0
MAX_COUNT=$1
 
typeset -x COPID=
 
echo "ENTER WHILE $$ at `date`"
 
while [[ $LOOP_COUNT < $MAX_COUNT  ]]; do
 
echo "LOOP IS $LOOP_COUNT , $MAX_COUNT"
 
(( TOTAL_PROC  += 1 ))
do_child  & COPID="$COPID $!"  # capture PID of coprocess
trap  child_exit_handler CHLD
 
echo "Inside while total $TOTAL_PROC "
(( LOOP_COUNT  += 1 ))
done
echo "Outside while total before wait $TOTAL_PROC "
 
wait
echo "Outside while total after wait $TOTAL_PROC "
echo "EXIT WHILE $$ at `date`"