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)

Investigating memory with GDB

With GDB, we can learn more about how things work under the hood, for example, strings. A string is an array of characters terminated by a null character. In this recipe, we'll investigate a character array with GDB and see how the null character ends a string.

Knowing how to examine the memory using GDB can be really handy if you encounter weird bugs. Instead of guessing or looping over each character in C, we can directly examine them in GDB.

Getting ready

For this recipe, you'll need the Makefile we wrote in the Starting GDB recipe. You'll also need the GCC compiler and the Make tool.

How to do it…

In this recipe, we'll write a simple program that fills a character array with the character x. Then we'll copy a new, shorter string on top of that and finally print the string. It's only the newly copied string that is printed, even if all the x characters are still there. With GDB, we can confirm this...