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)

Creating a daemon

A common assignment when working with system programming is to create various daemons. A daemon is a background process that runs on the system and performs some tasks. The SSH daemon is a great example of this. Another great example is the NTP daemon, which takes care of synchronizing the computer clock and sometimes even distributing the time to other computers.

Knowing how to create a daemon will enable you to create server software; for example, web servers, chat servers, and more.

In this recipe, we will create a simple daemon to demonstrate some important concepts.

Getting ready

You'll only need the components listed in the Technical requirements section of this chapter.

How to do it…

In this recipe, we'll write a small daemon that will run in the background in our system. The only "work" the daemon will do is write the current date and time to a file. This proves that the daemon is alive and well. Let's get...