Job Control: bg, fg, jobs

Run a thing without blocking the prompt

Append & to put a command in the background of your shell. The prompt returns immediately; the job keeps running. jobs lists what your shell knows about; fg brings one back to the foreground; bg resumes a stopped job in the background.

The flow

./long-build.sh &        # start in background
jobs                          # list with [N] tags
fg %1                         # bring job 1 to foreground
Ctrl+Z                        # suspend it
bg %1                         # resume in background
fg %1                         # back to foreground
kill %1                       # end it

Job IDs vs PIDs

%1 = job 1 of this shell. kill %1 kills it. jobs -l shows the underlying PIDs if you want to use them with ps or kill from another shell.

Disowning

By default, when you close the terminal, the shell sends SIGHUP to all its jobs. disown %1 detaches the job so it survives the shell's death. nohup ./script & at start does the same plus redirects output to nohup.out.

When to reach for tmux instead

For long-running things you might want to come back to tomorrow, use a tmux session (next-but-one lesson). Job control is for the now-and-here; tmux is for multi-session persistence.