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)

Moving around inside a file with fseek()

Now that we have seen how to seek inside a file descriptor with lseek(), we can see how we can do so in file streams with fseek(). In this recipe, we will write a similar program to that of the previous recipe, but now we will use file streams instead. There will also be another difference here, namely, how we specify how long we want to read. In the previous recipe, we specified the third argument as the number of characters or bytes to read. But in this recipe, we will instead specify a position, that is, a from position and a to position.

Getting ready

I advise you to read the Reading from files with streams recipe earlier in this chapter before reading this one. That will give you a better understanding of what's going on here.

How to do it…

We will write a program that reads a file from a given position and optionally to an end position. If no end position is given, the file is read to the end:

  1. Write the...