The Shell

In Unix the shell is a program which prompts the user and directs the operating system to do what the user wants. When you login to your account or open a new terminal, you see a prompt like [bbadger@demo01] (1)$ . This means that the shell is waiting for you to type a command. The shell is not Unix (and neither is X windows). It is merely a user interface to Unix and a program like any other. However, it is essential to know this user interface to become proficient in Unix.

Your user account is configured with tcsh, an enhanced version of the Berkeley UNIX C shell, csh. If you would like to use one of the many alternate shells, you can use the chsh command to change the shell your account uses.

The shell is a very powerful tool that can be customized. Using just tcsh, new commands can be created, old ones altered, input and output files dynamically redefined, and even entire programs written without ever using a compiler. Chapter  contains a number of useful hints to get more out of the shell. Consult the manual page for tcsh (see chapter , Getting Help) for more information on the many features.