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 zombie process

To fully understand processes in Linux, we also need to look at what a zombie process is. And to fully understand what this is, we need to create one ourselves.

A zombie process is a child that has exited before the parent, and the parent process hasn't waited for the child's status. The name "zombie process" comes from the fact that the process is undead. The process has exited, but there is still an entry for it in the system process table.

Knowing what a zombie process is and how it's created will help you avoid writing bad programs that create zombie processes on the system.

Getting ready

For this recipe, you'll only need what's listed in the Technical requirements section of this chapter.

How to do it…

In this recipe, we will write a small program that creates a zombie process on the system. We will also view the zombie process using the ps command. To prove that we can avoid zombies by waiting...