I learned how to spawn background process in bash and wait for them to finish.

Take the following script, we have to 2 process that slow and running sequentially.

process1_fn() {
  echo "Hello from process 1";
  sleep 5;
  echo "End of process 1"
}

process2_fn() {
  echo "Hello from process 1";
  sleep 5;
  echo "End of process 1"
}

process1_fn
process2_fn

How do we make them run concurrently? We can kick of each process independently using & operator. We can use wait command to wait for all the process to end.

process1_fn() {
  echo "Hello from process 1";
  sleep 5;
  echo "End of process 1"
}

process2_fn() {
  echo "Hello from process 2";
  sleep 5;
  echo "End of process 2"
}

process1_fn &
process2_fn &

wait

Context: I ran into this problem while deploying multiple cloud functions in Google Cloud Build. Deploying each cloud function takes about 3 mins. So, I used this technique to reduce my deployment time.