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)

Chapter 2: Making Your Programs Easy to Script

Linux and other Unix systems have strong scripting support. The whole idea of Unix, from the very beginning, was to make a system easy to develop on. One of these features is to take the output of one program and make it the input of another program—hence building new tools with existing programs. We should always keep this in mind when creating programs for Linux. The Unix philosophy is to make small programs that do one thing only—and do it well. By having many small programs that do only one thing, we can freely choose how to combine them. And by combining small programs, we can write shell scripts—a common task in Unix and Linux.

This chapter will teach us how to make programs that are easy to script and easy to interact with other programs. That way, other people will find them much more useful. It's even likely they will find new ways of using our programs that we haven't even thought of, making the programs more popular and easier to use.

In this chapter, we will cover the following recipes:

  • Return values and how to read them
  • Exiting a program with a relevant return value
  • Redirecting stdin, stdout, and stderr
  • Connecting programs using pipes
  • Writing to stdout and stderr
  • Reading from stdin
  • Writing a pipe-friendly program
  • Redirecting the result to file
  • Reading environment variables

Let's get started!