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)

Using errno with perror()

In the previous recipe, we used strerror() to get a string containing a human-readable error message from errno. There's another function similar to strerr() called perror(). Its name stands for print error, and that's what it does; it prints the error message directly to stderr.

In this recipe, we'll write the sixth version of our simple touch program. This time, we'll replace both of the fprinf() lines with perror().

Getting ready

The only programs necessary for this recipe are the GCC compiler and the Make tool (along with the generic Makefile).

How to do it…

Follow these steps to create an even shorter and better version of simple-touch:

  1. Write the following code into a file and save it as simple-touch-v6.c. This time, the program is even smaller. We have removed the two fprintf() statements and replaced them with perror() instead. The changes from the previous version are highlighted here:
    #include <stdio...