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)

Writing to files with streams

In this recipe, we will write to files using file streams instead of file descriptors, as we did in earlier recipes.

As with the previous recipes where we had already seen file descriptors 1, 2, and 3, and some of their system calls, we have already seen file streams too, such as some of the printUsage() functions we have created. Some of these functions we created took two arguments, the first one being declared as FILE *stream. The argument we provided was stderr or stdout.

But we can also use file streams to write to files, which we will do in this recipe.

As you probably have noticed by now, some things keep coming again and again, such as file descriptors and file streams.

Working with file streams instead of file descriptors has some advantages. For example, with file streams, we can use functions such as fprintf() to write to files. This means that there are more—and more powerful—functions to read and write data.