Summary
Now that you have completed this chapter, you should have a firm understanding of the following:

The UNIX shell is a key component of the UNIX operating system. The shell is the interface between the user and the kernel. There are 3 commonly used shells: The Bourne shell, the Korn shell, and the C shell. This chapter focused on the Korn and C shells, which have more features than the Bourne and are the most popular for regular users.

The default prompt for the Korn shell is the dollar sign $ (same as Bourne shell). The default prompt for the C shell is the percent sign %. Both the Korn and C shell users can customize their prompts. The Korn shell sets the PS1 variable and the C shell uses the set prompt command.

Both Korn and C shells support aliasing and history, although their command syntax varies somewhat. Aliases allow the user to create new command names and associate them with existing commands to increase productivity. The
history command allows the user to re-use previous commands to avoid having to type them in again.

The Korn shell provides command line editing by allowing the user to use vi editor commands to modify previous command lines. The C shell allows the user to make command line substitutions for simple changes but does not have a command line editing feature like the Korn shell.