out.txt is what my shell looks like, trap.sh receives SIGINTS, sending a SIGTERM to the most recently forked loop.sh

loop.sh

#!/bin/bash

trap 'echo "loop $$ recieved SIGTERM; exiting" && exit' SIGTERM

for i in `seq $1 -1 1`; do
        echo count = $i in loop $$
        sleep 1s
done

out.txt

chronos@localhost ~ $ sudo enter-chroot ./trap.sh
Entering /mnt/stateful_partition/crouton/chroots/unity...
count = 6 in loop 2819
count = 4 in loop 2817
count = 5 in loop 2818
count = 5 in loop 2819
count = 4 in loop 2818
count = 3 in loop 2817
^CTRAP SIGINT, sending TERM to 2819
 2815  2819 /bin/bash ./loop.sh 6
loop 2819 recieved SIGTERM; exiting
count = 3 in loop 2818
count = 2 in loop 2817
^CTRAP SIGINT, sending TERM to 2818
 2815  2818 /bin/bash ./loop.sh 5
loop 2818 recieved SIGTERM; exiting
count = 1 in loop 2817
Not unmounting /mnt/stateful_partition/crouton/chroots/unity as another instance is using it.
chronos@localhost ~ $ 

trap.sh

#!/bin/bash

trap_int() {
        index=$((${#loop[@]}-1))
        echo TRAP SIGINT, sending TERM to ${loop[$index]} >&2
        ps -o ppid= -o pid= -o cmd= ${loop[$index]}
        kill ${loop[$index]}
        unset loop[$index]
}
all_done() {
        if [ ${#loop[@]} -eq 0 ]; then
                return 0
        else
                for l in ${loop[@]}; do
                        kill -0 $l &>/dev/null && return 1
                done
                return 0
        fi
}
trap 'trap_int' SIGINT

for i in `seq 3`; do
        ./loop.sh $((i+3)) & loop[$((i-1))]=$!
done
while true; do
        all_done && sleep 2s && exit
        sleep 0.5s
done