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)

Causing a race condition

A race condition is when more than one thread (or process) tries to write to the same variable simultaneously. Since we don't know which thread will access the variable first, we can't safely predict what will happen. Both threads will try to access it first; they will race to access the variable.

Knowing what's causing a race condition will help you avoid them, making your programs safer.

Getting ready

For this recipe, you'll only need the Makefile we wrote in the first recipe of this chapter, along with the GCC compiler and the Make tool.

How to do it…

In this recipe, we'll write a program that causes a race condition. If the program were to work properly, it should add 1 to the i variable on every run, ending up at 5,000,000,000. There are five threads, and each thread adds 1 up to 1,000,000,000. But since all the threads access the i variable simultaneously—more or less—it never reaches 5,000...