Linux Command Line and Shell Scripting Bible, 3rd Edition

Working with Alternative Shells

IN THIS CHAPTER

Understanding the dash shell

Programming in the dash shell

Introducing the zsh shell

Writing scripts for zsh

Although the bash shell is the most widely used shell in Linux distributions, it isn't the only one. Now that you've seen the standard Linux bash shell and what you can do with it, it's time to examine a few other shells available in the Linux world. This chapter describes two other shells that you may run into in your Linux journey and how they differ from the bash shell.

What Is the dash Shell?

The Debian dash shell has had an interesting past. It's a direct descendant of the ash shell, a simple copy of the original Bourne shell available on Unix systems (see Chapter 1). Kenneth Almquist created a small-scale version of the Bourne shell for Unix systems and called it the Almquist shell, which was then shortened to ash. This original version of the ash shell was extremely small and fast but without many advanced features, such as command line editing or history features, making it difficult to use as an interactive shell.

The NetBSD Unix operating system adopted the ash shell and still uses it today as the default shell. The NetBSD developers customized the ash shell by adding several new features, making it closer to the Bourne shell. The new features include command line editing using both emacs and vi editor commands, ...