What is Bash?

Bash's full name is the GNU Bourne Again Shell. It is a programming language, specifically a shell scripting language, with an interpreter in a program named bash. It was created by Brian Fox of the Free Software Foundation, starting in 1989, and is now maintained by Chet Ramey. It is part of the GNU project for a free software operating system.

The bash program is used as a shell: either for entering commands as an interactive shell using a command line, batches of commands from a shell script, or a single command from an option.

In this book, we will refer to Bash as the software distribution and the programming language, and to bash as its interpreter program.

Bash is a Bourne-style shell, with some support for POSIX shell compatibility. It is not compatible with any kind of C-style shell, such as tcsh.

Bash has many general programming language facilities that make it usable for general programming tasks, but like most shell scripting languages, its fundamental design is to run other programs in a control structure, and to make them work together in ways suitable to the programmer, whether or not they were designed to do so. This is the main thing that makes shell scripting powerful and useful.

In this chapter, you will learn:

• What Bash is and is not
• How to install and switch to Bash
• How to check you are running a recent version of Bash
• How the POSIX standard applies to Bash
• The two major categories of Bash features
• Programming tasks for which Bash is and is not well-suited
• How to get help while using Bash