Shell Scripting: Expert Recipes for Linux, Bash, and More

The Bourne Shell

When Unix was first born, it had a very basic shell written by Ken Thompson, one of the creators of Unix. The Bourne shell was written by Steve Bourne in 1979 as a scriptable Unix shell. All other shells have a prefix to qualify which shell they are — ksh, csh, zsh, and so on — but the Bourne shell does not call itself bsh because it simply is “the shell,” so its canonical path is /bin/sh. Other shells came along later with more features, while staying generally compatible with the Bourne shell — some more compatible than others.

One of the most significant new concepts that the Bourne shell provided was the pipeline, the structure that allows one process to pass its output to the input of another process. This was a dramatic change in the capability of a shell command. Bourne also introduced variables and flow control, turning the shell from being a very basic command interpreter into a flexible scripting language.