Background Jobs

Advanced~25 min read

Run tasks concurrently with &, track PIDs, and wait for completion. In non-interactive shells, prefer wait over interactive fg/bg.

Starting and Waiting

Output

Click Run to execute your code

Note: $! expands to the PID of the most recent background command.

Pro Tip: Use descriptive logging including job IDs and timestamps.

Caution: fg/bg require interactive job control; they are not available in many non-interactive environments.

Store PIDs immediately after launching background tasks.

Check $? after wait to detect job errors.

Task: Start two sleep commands in the background and wait for both to complete.

Output

Click Run to execute your code

Show Solution

sleep 1 & pid1=$!; sleep 2 & pid2=$!; wait "$pid1" "$pid2"

Diagnose issues and trace execution in Debugging.