Process Management

Background and Wait

Collecting Status

& starts a command in the background. $! records its process id, and wait collects the final exit status.

Program

Play the script to start a short background job and collect its selected status.

background_wait.sh 
#!/usr/bin/env bash

job_status=
(exit "$job_status") &
pid=$!
wait "$pid"
status=$?
echo "status=$status"

#!/usr/bin/env bash

job_status=
(exit "$job_status") &
pid=$!
wait "$pid"
status=$?
echo "status=$status"

#!/usr/bin/env bash

job_status=
(exit "$job_status") &
pid=$!
wait "$pid"
status=$?
echo "status=$status"
background job `command &` starts a command and immediately returns control to the script.
$! `$!` stores the process id of the most recent background command.
wait `wait "$pid"` pauses until that process finishes and returns its status.