Jobs & Signals

Foreground vs background

A foreground job occupies your terminal until it finishes. A background job (started with &) frees the terminal so you can keep working.

&, jobs, fg, bg

Start a job in the background, list jobs, and bring one back to the foreground.

sleep 100 &
jobs
fg %1        # bring job 1 to foreground
# Ctrl+Z suspends the foreground job, then:
bg %1        # resume it in background

Output:

[1] 5231
[1]+  Running                 sleep 100 &

Signals at a glance

SIGINT (Ctrl+C) asks a process to stop, SIGTERM (default kill) requests graceful shutdown, SIGKILL (-9) terminates immediately and cannot be caught or ignored.

Quick check: Which signal cannot be caught or ignored by a process?

• SIGTERM
• SIGINT
• SIGKILL