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 from files with file descriptors

In the previous recipe, we learned how to write to files using file descriptors. In this recipe, we will learn how to read from files using file descriptors. We will therefore write a small program that is similar to cat. It takes one argument—a filename—and prints its content to standard output.

Knowing how to read—and use—file descriptors enables you to read not only files but all sorts of data that comes through a file descriptor. File descriptors are a universal way to read and write data in Unix and Linux.

Getting ready

The only things you'll need for this recipe are listed under the Technical requirements section of this chapter.

How to do it…

Reading a file using a file descriptor is similar to writing to one. Instead of using the write() system call, we will instead use the read() system call. Before we can read the content, we must figure out the size of the file first. We can use...