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)

Message queues – creating the sender

Another popular IPC technique is message queues. It's pretty much what the name suggests. A process leaves messages in a queue, and another process reads them.

There are two types of message queues available on Linux: System V and POSIX. In this recipe, we'll cover POSIX message queues since these are a bit more modern and simpler to handle. POSIX message queues are all about using the mq_ functions, such as mq_open(), mq_send(), and so on.

Knowing how to use message queues enables you to choose from among a variety of IPC techniques.

Getting ready

For this recipe, we'll only need the GCC compiler and the Make tool.

How to do it…

In this recipe, we'll create the sender program. It's this program that will create a new message queue and some messages to it. In the next recipe, we'll receive those messages:

  1. Write the following code in a file and save it as msg-sender.c. Since there...