Book Image

Linux System Programming Techniques

By : Jack-Benny Persson
Book Image

Linux System Programming Techniques

By: Jack-Benny Persson

Overview of this book

Linux is the world's most popular open source operating system (OS). Linux System Programming Techniques will enable you to extend the Linux OS with your own system programs and communicate with other programs on the system. The book begins by exploring the Linux filesystem, its basic commands, built-in manual pages, the GNU compiler collection (GCC), and Linux system calls. You'll then discover how to handle errors in your programs and will learn to catch errors and print relevant information about them. The book takes you through multiple recipes on how to read and write files on the system, using both streams and file descriptors. As you advance, you'll delve into forking, creating zombie processes, and daemons, along with recipes on how to handle daemons using systemd. After this, you'll find out how to create shared libraries and start exploring different types of interprocess communication (IPC). In the later chapters, recipes on how to write programs using POSIX threads and how to debug your programs using the GNU debugger (GDB) and Valgrind will also be covered. By the end of this Linux book, you will be able to develop your own system programs for Linux, including daemons, tools, clients, and filters.
Table of Contents (14 chapters)

Writing a unit file for a daemon

In this recipe, we will take the daemon we wrote in Chapter 6, Spawning Processes and Using Job Control, and make it a service under systemd. This daemon is what systemd calls a forking daemon because it does just that. It forks. This is traditionally how daemons have worked, and they are still widely used. Later in this chapter, in the Making the new daemon a systemd service section, we will modify it slightly to log to systemd's journal. But first things first, let's make our existing daemon into a service.

Getting ready

In this recipe, you'll need the file my-daemon-v2.c that we wrote in Chapter 6, Spawning Processes and Using Job Control. If you don't have that file, there is a copy of it in this chapter's directory on GitHub at https://github.com/PacktPublishing/Linux-System-Programming-Techniques/blob/master/ch7/my-daemon-v2.c.

Apart from my-daemon-v2.c, you'll need the GCC compiler, the Make tool, and the...