Signals

One line: Ctrl-C is not a command, it is SIGINT — and a program that has taken SIGINT over keeps counting while you press it. Which key sends which signal, which signals a shell can trap, and the two that no process in any language can catch, block or ignore.

Lesson	Level	What it settles
The signals you cannot catch	201	trap in bash and zsh and --on-signal in fish, the trap … KILL all three accept and none can honour, exit status 128 + N, SIGSTOP and SIGCONT, and the third way a handler silently never runs — where bash and zsh disagree

Planned

Rough order, not a promise:

• The keys are terminal settings: stty -a naming intr, quit and susp, and what changes when you point them somewhere else
• Job control: &, jobs, fg, bg, %1, and the three job-control signals a shell sends behind them
• nohup, disown and SIGHUP: what happens to a background job when the terminal goes away, and the nohup.out you did not ask for
• What a shell prints when a job dies: Quit, suspended, Terminated, the [1] + bookkeeping, and why bash and zsh word it differently