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)

Executing a new program in a forked process

In the previous recipe, we learned how to fork a process using the fork() system call. In the recipe before that, we learned how to replace the program in a process with execl(). In this recipe, we'll combine the two, fork() and execl(), to execute a new program in a forked process. This is what happens every time we run a program in Bash. Bash forks itself and executes the program we typed in.

Knowing how to use fork() and execl() enables you to write programs that start new programs. For example, you could write your own shell with this knowledge.

Getting ready

For this recipe, you'll need the pstree tool, the GCC compiler, and the Make tool. You can find installation instructions for these programs in the Technical requirements section of this chapter.

How to do it…

In this recipe, we'll write a program that forks() and executes a new program in the child process. Let's get started:

  1. Write...