#! /bin/sh
# 
SIG=15
echo "\
Correct order is:
 parent waiting on \$childpid
 child sending signal to \$parentpid
 parent received signal
 wait #1 finished, gotsig=1, status=a number > 128, possibly $(($SIG+128))
 child exiting
 wait #2 finished, gotsig=0, status=33
"
gotsig=0
signal_handler() {
 echo "parent received signal"
 gotsig=1
}
child() {
 sleep 2
 echo "child sending signal to pid $parentpid"
 kill -$SIG $parentpid
 sleep 2
 echo "child exiting" 
 exit 33
} 
parentpid=$$
echo "parent's pid is $parentpid"
child &
childpid=$!
trap signal_handler $SIG
echo "parent waiting on pid $childpid"
wait $childpid
cstatus=$?
echo "wait #1 finished, gotsig=$gotsig, status=$cstatus"
gotsig=0
wait $childpid
cstatus=$?
echo "wait #2 finished, gotsig=$gotsig, status=$cstatus"