Once you have set your terminal type, the computer shows you a command prompt. This is where you type commands during the rest of your work session. Each time you press <Enter>, you see a new command prompt. The prompt you see depends on the login shell you are using.
All the time that you are working on the UNIX system, you are working within a shell. When you log in, you are automatically placed within a shell; this is called your login shell. Shells are both command interpreters and programming languages. Each command line you type is interpreted by the shell, which passes your requests to the appropriate program for processing.
For most of this tutorial, you will be using shells only as command interpreters. In other words, you will be typing commands at the prompt and seeing what they do.
In ``Customizing your environment'' you will be introduced to the concept of a shell script. These are text files that contain shell language programs.
There are three shells distributed with your SCO OpenServer system:
By default (unless someone has changed it), the Bourne and Korn shells show a dollar sign ($) as a command prompt. The C shell shows a percent sign (%) by default.
(You can change your prompt by editing a file that the computer reads when you log in. See ``Customizing your environment'' for instructions.)
If you cannot tell which shell you are using from the prompt, you can ask the computer by typing echo $SHELL. This says, ``tell me the value of the variable SHELL.'' The computer responds with an answer like:
/bin/shThe last part is the name of the shell, sh (the Bourne shell), and the first part is the directory in which it lives.