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4 Command structure in GRASS

The commands follow a very clear structure in GRASS. The type of a command can be recognized by the abbreviation in front of the first period (prefix). Commands, which are independent programs are called modules in GRASS. They have self-describing names. Thus, the module for digitalizing raster maps is called r.digit. In order to convert vector data into raster format the module v.to.rast is used. Table 1 describes the structure of the names of GRASS commands and modules in detail.

Modules and programs under GRASS

Apart from the modules existing in GRASS, all Unix/Linux programs are available. They can be recalled via Shell, the command interpreter. This is particularly useful if you are interested in programming, integrating or modifying your own and/or available GRASS modules. Even if it may seem difficult to the beginner the ability of a user to program in GRASS provides nearly unrestricted possibilities to realize their own needs and imagination within GIS. In addition, creating simple Unix/Linux Shell scripts is easy to learn.

Table 1: Structure of the GRASS module names

Prefix	Function class	Meaning of the commands
d.*	display	For graphical display and visual query at the monitor
r.*	raster	For raster data processing
i.*	imagery	For image processing
v.*	vector	For vector data processing
g.*	general	General file operation commands
p.*	paint	Map design commands
ps.*	postscript	Map design commands for postscript size
db.*	database	Database management modules
r3.*	voxel raster	For 3D raster data processing