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)

Modifying variables during runtime

With GDB it's even possible to modify variables during runtime. This can be very handy for experimentation. Instead of changing the source code and recompiling the program, you can change the variable with GDB and see what happens.

Knowing how to change variables and arrays during runtime can speed up your debugging and experimentation phase.

Getting ready

For this recipe, you'll need the memtest.c program from the previous recipe. You'll also 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 continue using the program from the previous recipe. Here, we'll replace the null character in the sixth place with another character and the last character with a null character:

  1. If you haven't yet compiled the memtest program from the previous recipe, do so now:
    $> make memtest
    gcc -g -Wall -Wextra -pedantic -std...