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GRASS is a software package designed to run under various UNIX
compliant systems, such as GNU/Linux, SUN-Solaris, Irix, and MacOS X,
as well as under MS-WindowsNT/2000/XP (currently with Cygwin). Both
32 bit and 64 bit architectures are supported. Effective use of GRASS
therefore requires certain familiarity with UNIX and adequate computer
hardware. Nowadays the usage of GNU/Linux systems is rather
straightforward due to the development of common graphical user
interfaces (like the KDE environment), where you can start programs
from menu driven GUI environments. However, it is useful to learn how
to launch commands from a terminal window (command line), as this
greatly extends functionality. In particular, users can combine GRASS
commands with shell and other system commands to create powerful
scripts, without having to learn additional programming languages.
After opening a terminal window you will see the prompt, for example,
[yourname@yourmachine]
or something similar (the appearance of the prompt can be customized). Here you can enter UNIX commands and start applications. Within the terminal window, the so called ``shell'' interprets your commands. It receives the commands from the keyboard and transfers them to the operating system. The shell is loaded automatically when you open a terminal window. There are different shells available: C-shell (csh), bash, and the tcsh. All shells will accept every command, but they differ in their behavior, for example, how they handle cursor keys and file name completion.
Automatic file name completion saves a lot of typing because you only need to input the first character(s) of the file or command name and the shell will complete it after pressing the shell-specific completion key. The name completion key in tcsh is <ESC> (press twice), in bash it is <TAB>. Previous commands can be selected and edited with <Arrow-up> and <Arrow-down>. Also, you can transfer text from a terminal window to another one using ``copy-and-paste'' functions with a mouse. Use the left mouse button to mark and copy the text, then drop it wherever you need it using the middle or right mouse button (paste).