linux - shell - get exit code of background process -

i have command cmd called main bourne shell script takes forever.

i want modify script follows:

1. run command cmd in parallel background process ($cmd &).
2. in main script, have loop monitor spawned command every few seconds. loop echoes messages stdout indicating progress of script.
3. exit loop when spawned command terminates.
4. capture , report exit code of spawned process.

can give me pointers accomplish this?

1: in bash, $! holds pid of last background process executed. tell process monitor, anyway.

4: wait <n> waits until process id complete (it block until process completes, might not want call until sure process done). after wait returns, exit code of process returned in variable $?

2, 3: ps or ps | grep " $! " can tell whether process still running. how understand output , decide how close finishing. (ps | grep isn't idiot-proof. if have time can come more robust way tell whether process still running).

here's skeleton script:

# simulate long process have identifiable exit code (sleep 15 ; /bin/false) & my_pid=$!  while   ps | grep " $my_pid "     # might need  | grep -v grep  here     echo $my_pid still in ps output. must still running.     sleep 3 done  echo oh, looks process done. wait $my_pid my_status=$? echo exit status of process $my_status