In this chapter, the reader has been taken through the various interfaces exposed by Linux with regard to creating and using timers. Setting up and managing timeouts is an essential component of many, if not most, systems applications. The older interfaces—the venerable alarm(2) API, followed by the [s|g]etitimer(2) system calls—were shown with example code. Then, we delved into the newer and better POSIX timers, including the advantages provided by them, and how to use them in a practical fashion. This was greatly aided with the help of two fairly elaborate sample programs—the react game and the run:walk timer application. Finally, the reader was introduced to the notion of using timers via file abstractions, and to the watchdog timer.

The next chapter is where we begin our long three-chapter journey on understanding and using the powerful multithreading framework on Linux.