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)

Using signals for IPC – building a client for the daemon

We have already used signals several times in this book. However, when we did, we always used the kill command to send the signal to the program. This time, we'll write a small client that controls the daemon, my-daemon-v2, from Chapter 6, Spawning Processes and Using Job Control.

This is a typical example of when signals are used for IPC. The daemon has a small "client program" that controls it, so that it can stop it, restart it, reload its configuration file, and so on.

Knowing how to use signals for IPC is a solid start in writing programs that can communicate between them.

Getting ready

For this recipe, you'll need the GCC compiler, the Make tool, and the generic Makefile. You will also need the my-daemon-v2.c file from Chapter 6, Spawning Processes and Using Job Control. There is a copy of that file in this chapter's GitHub directory at