Disappointingly this book doesn't cover signals: SIGINT, SIGTERM, SIGUSR1, SIGABORT. It shows how to "trap" (set up a signal handler) from a shell script, but not in a program, where it is significantly more complex and unintuitive (signal masks, per-thread signals versus per-process ones, etc.). There's the use of "kill" to send a signal, which is a poor name: what about signals that don't kill? What's the difference between a STOP signal and a TSTP? The latter is Terminal SToP, it's what you send when you hit CTRL-Z and immediately have no idea how to get your long-running task back.
In fact, nothing about IPC at all in this book, I guess it's considered a programmer topic.