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)

Writing a program that parses command-line options

In this recipe, we will create a more advanced program—one that parses command-line options. In the previous recipe, we wrote a program that parsed arguments using argc and argv. We will use those variables here as well, but for options. Options are the hyphenated letters, such as -a or -v.

This program is similar to the previous one, with the difference that this program can both this; -s for "sum" and -m for "multiply."

Almost all programs in Linux take different options. Knowing how to parse options to the programs you create is a must; that is how the user changes the behavior of your program.

Getting ready

All you need is a text editor, the GCC compiler, and Make.

How to do it…

Since this source code will be a bit longer, it will be broken up into three pieces. The entire code goes into the same file, though. The complete program can be downloaded from GitHub at https://github...