The Common Shells

The original UNIX System shell, sh, was written by Steve Bourne, and as a result it is known as the Bourne shell. Because it was the first, the Bourne shell lacks many enhancements common to the later shells. It can still be useful for certain tasks (such as scripting, described in Chapter 20), but almost all users will prefer one of the newer shells for entering commands.

The C shell, csh, was the first attempt to enhance the original Bourne shell. The syntax was strongly influenced by the C programming language. The C shell introduced the concepts of a command history list, job control, and aliases. However, like sh, it lacks some important features of later shells. A common complaint about csh is that the new syntax is not compatible with the Bourne shell, and so some scripts may not work properly in csh.