Shells and Commands

Shells

Users rarely use UNIX directly, however. The utility software that interprets a user's commands for the kernel is called the shell. Here too, there are several flavors. While graphical shells exist for UNIX that imitate the Apple Macintosh or MIcrosoft Windows, most users stick with the traditional command line interface. You type commands one by one on your terminal or into a terminal window, press RETURN, and they are executed. The original and most common shell is the Bourne shell. The C-shell is newer and provides an extensive command language similar to the C programming language. The Korn shell attempts to combine the best of both earlier shells. More than one shell is often available to users on a UNIX system.

Here at the UW-Madison Math Department we use a shell called tcsh that has several improvements over the original C shell.

Using UNIX Commands

UNIX commands follow the format: command -flags arguments. The commands are one-word, lowercase. Optional flags are one-letter switches that modify the way the command works. They follow the dash, are case-sensitive, and can be combined. The optional argument usually specifies the file or directory that is the target of the command's action. Hit RETURN after entering a command.

Here are a bunch of useful commands, but if you want to know even more, check out the friendly and extensive UNIXhelp for Users. In the examples commands below, the following notation is used.

• • Double quotes “...” enclose special characters and some examples. Don't type these quotes in a command! When you need to type quotes we'll tell you.

  • The symbol “^” indicates the control key. For example, “^C” means press CONTROL and C at the same time.

  • Italicized words denote generic arguments, such as filenames. Don't type the italicized words. Instead, type in an appropriate filename, directory, etc.