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)

Using shared memory between unrelated processes

In the previous recipe, we used shared memory between a child and a parent. In this recipe, we'll learn how to use a file descriptor to mapped memory to share that memory between two unrelated processes. Using shared memory in this way automatically creates an underlying file for the memory in the /dev/shm directory, where shm stands for shared memory.

Knowing how to use shared memory between unrelated processes widens your use of this IPC technique.

Getting ready

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

How to do it…

First, we'll write a program that opens and creates a file descriptor for shared memory and also maps the memory. Then, we'll write another program that reads the memory area. Instead of just a message, as we did in the previous recipe, we'll write and retrieve an array of three floating-point numbers here.

Creating the writer

Let's create...