Introduction

A shell is basically a program that handles user commands and starts other programs. The term "shell" is another one of those weak UNIX jokes; the "shell" is the program between you and the "kernel." After you log in, the shell prompt is the first thing you see. There are a lot of different shells available for Linux (e.g., Korn, Bourne, csh, tcsh); which particular one you use at login time is determined by your entry in the /etc/passwd file (it's the rightmost field on the line). One's choice of shell isn't quite the wellspring of jihad that one's choice of operating system is, but it is still a semi-touchy issue.

Bash stands for Bourne Again SHell, a reference to the fact that bash is based on another shell (the Bourne shell, obviously). Bash contains features found in the Bourne shell, csh (the C shell), the Korn Shell, and some features that are found in bash only. All of the Bourne shell built-in commands are available in bash.