Summary

The main focus of this chapter was to provide a considerable level of understanding of the shell programming fundamentals to Linux system users. The chapter focused its attention on the borne again shell or the bash shell. Programming the shell enables the Linux users to interact with the operating system in a friendly and proficient way. Shell programming is a requirement for any type of users, whether they are administrators, developers, or desktop users. Among these different categories of users, the desktop users probably do not use as much of the shell programming features, but knowledge of the shell certainly helps them to customize the desktop as they prefer.

The chapter began with a discussion on the shell fundamentals, including executable scripts, understanding the system PATH, exporting variables, standard input, output and error streams, redirecting these streams to files or other streams, and so on. Then the discussion continued with the concepts of a user’s login environment, how to create and maintain global shell variables during the user’s login shell, predefined shell variables, how the shell maintains a history of commands entered by the user, and creating alias names for complex command lines.

Following this discussion, the chapter focused on expressions, functions, and other shell scripting constructs that provide flow control and a program-like structure to enable the users to write powerful shell scripts, including conditional and looping constructs.