The Command Line Interpreter (CLI)

In Windows, if you type a command which is not understood, you get a response

……. is not recognized as an internal or external command, operable program, or batch file.

I assume you are using a server version of Linux/Unix and that you know how to get to the command prompt. If you are using a GUI version of Ubuntu, press [ctrl][t] to open a terminal.

In Unix the equivalent response will be command not found, although other error messages are possible. Sometimes this will happen after you type a perfectly good command name. If the operating system does not know where to find the command, it will give you this error. More about this when we look at environment variables a little bit later.

You need to be aware of the computer's response as we are going along. If the computer responds to a command with an error, go back and check the command again, it probably hasn't been carried out.

To find out what version of operating system you are running,

In the Unix shell type uname and press return

Note that

• All commands and file names in Unix are case sensitive.

• All commands and file names in DOS are NOT case sensitive.