How to get list of all child process spawned by a script

To answer your question directly, the command

jobs -p

gives you the list of all child processes.

Alternative #1

But in your case it might be easier to just use the command wait without any params:

first_program &
second_program &
wait

This will wait until ALL child processes have finished.

Alternative #2

Another alternative is using $! to get the PID of the last program and perhaps accumulate in a variable, like so:

pids=""
first_program &
pids="$pids $!"
second_program &
pids="$pids $!"

and then use wait with that (this is in case you only want to wait for a subset of you child processes):

wait $pids

Alternative #3

OR, if you want to wait only until ANY process has finished, you can use

wait -n $pids

Bonus info

If you want a sigterm to your bash script to close your child processes as well, you will need to propagate the signal with something like this (put this somewhere at the top, before starting any process):

trap 'kill $(jobs -p)' SIGINT SIGTERM EXIT