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)

Reading and writing binary data with streams

There comes a time when we must save variables or arrays in a program to a file. For example, if we make a stock-keeping program for a warehouse, we don't want to re-write the entire warehouse stocks every time we start the program. That would defeat the purpose of the program. With streams, it's easy to save variables as binary data in files for later retrieval.

In this chapter, we'll write two small programs: one that asks the user for two floats, saves them in an array, and writes them to a file, and another program that re-reads that array.

Getting ready

You only need the GCC compiler, the Make tool, and the generic Makefile for this recipe.

How to do it…

In this recipe, we'll write two small programs: one that writes and one that reads binary data. The data is an array of floats:

  1. Write the following code in a file and save it as binary-write.c. Notice that we open the file in write mode...