Signals are a crucial mechanism for the Linux system developer to understand and exploit. We cover this rather large topic over two chapters in this book, this chapter and the next one. 

In this chapter, the reader is introduced to what signals are, why they are useful to the systems developer, and, most importantly of course, how exactly the developer is to handle and thus exploit the signalling mechanism.

We will continue this exploration in the next chapter.

In this chapter, the reader will learn the following:

• What exactly signals are.
• Why they are useful.
• The available signals.
• How exactly you can handle signals in an application, which really involves many things—blocking or unblocking signals, writing safe handlers, getting rid of pesky zombies once and for all, working with apps where the signal volume is high, and more.