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 GDB on a program that forks

Using GDB to debug a program that forks will automatically follow the parent process, just like a regular non-forking program. But it's possible to follow the child process instead, which is what we will learn in this recipe.

Being able to follow the child process is important in debugging since many programs spawn child processes. We don't want to limit ourselves to only non-forking programs.

Getting ready

For this recipe, you'll need the Makefile from the Starting GDB recipe in this chapter, the Make tool, and the GCC compiler.

How to do it…

In this recipe, we'll write a small program that forks. We'll put a for loop inside the child to confirm whether we are inside the child or the parent. On the first run in GDB, we'll run through the program like we usually would. This will make GDB follow the parent process. Then, in the next run, we'll follow the child process instead:

  1. Write the...