Question

How to wait in a bash script for several subprocesses spawned from that script to finish, and then return exit code !=0 when any of the subprocesses ends with code !=0?

Simple script:

#!/bin/bash for i in `seq 0 9`; do   doCalculations $i & done wait 

The above script will wait for all 10 spawned subprocesses, but it will always give exit status 0 (see help wait). How can I modify this script so it will discover exit statuses of spawned subprocesses and return exit code 1 when any of subprocesses ends with code !=0?

Is there any better solution for that than collecting PIDs of the subprocesses, wait for them in order and sum exit statuses?

Answer 1

wait also (optionally) takes the PID of the process to wait for, and with $! you get the PID of the last command launched in the background. Modify the loop to store the PID of each spawned sub-process into an array, and then loop again waiting on each PID.

# run processes and store pids in array for i in $n_procs; do     ./procs[${i}] &     pids[${i}]=$! done  # wait for all pids for pid in ${pids[*]}; do     wait $pid done