GRASS variables and environment variables

There are two types of variables:

environment variables,
GRASS variables.

Any setting which needs to be modifiable by a GRASS program (e.g. MONITOR) has to be a GRASS variable.

Setting environment variables

Setting environment variables depends on the shell being used:
  Bash:     export VARIABLE=value
   or
  Csh:      setenv VARIABLE value

Setting environment variables permanently

To get personal BASH shell definitions (aliases, color listing option, ...) into GRASS, store them in:
$HOME/.grass.bashrc
To get personal CSH shell definitions (aliases, color listing option, ...) into GRASS, store them in:
$HOME/.grass.cshrc

Setting GRASS variables

You have to use "g.gisenv" (within GRASS which then permanently predefines GRASS variables in the .grassrc6 file):

Use: g.gisenv set=VARIABLE=VALUE

It looks unusual with two equals signs, but g.gisenv does dual duty for getting and setting GRASS variables.

If the user just specifies a variable name, it defaults to "get" mode. Example:

GRASS ~> g.gisenv GRASS_GUI text

List of selected (GRASS related) environment variables

GISBASE
directory where GRASS lives

GISRC
name of .grassrc6 file

GRASS_ADDON_PATH
[grass5] startup script
allows to specify additional paths to local GRASS modules extra to standard distribution

GRASS_ANOTHER_BUTTON
[various modules]
If the environment variable GRASS_ANOTHER_BUTTON exists, the mouse button setting will be changed for two-button mice.

GRASS_BACKGROUNDCOLOR
[PNGdriver]
defines the background color of the image created by the PNG driver

GRASS_GNUPLOT
[m.svfit, s.probplt, s.sv]
program to use for plotting "gnuplot" data

GRASS_HEIGHT
[d.mon]
defines the height of GRASS monitor, see also GRASS_WIDTH

GRASS_HTML_BROWSER
[init.sh, d.m]
defines name of HTML browser

GRASS_INT_ZLIB
[libgis]
If the environment variable GRASS_INT_ZLIB exists, new compressed rasters will be compressed using zlib instead of RLE compression. Such rasters will have a "compressed" value of 2 in the cellhd file.
Obviously, decompression is controlled by the raster's "compressed" value, not the environment variable.

GRASS_MESSAGE_FORMAT
[various modules]
Maybe set to either "standard" or "gui" (normally GRASS takes care)

GRASS_PAGER
[various modules]
Maybe set to either "less" or "more"

GRASS_PERL
set perl with path

GRASS_PNGFILE
[PNGdriver]
name of PNG output file

GRASS_STDERR
set to any value to prevent user mail on error

GRASS_TCLSH
[nviz]
set tclsh shell name to override 'tclsh'

GRASS_TRANSPARENT
[PNGdriver]
if "TRUE", the image created by the PNG driver will have a transparent background

GRASS_TRUECOLOR
[PNGdriver]
if "TRUE", the PNG driver generates a true-color image

GRASS_UI_TERM
set to any value to use the terminal based parser

GRASS_VERSION
reports the current version number (used by R-stats interface etc);
should not be changed by user

GRASS_WIDTH
[d.mon]
defines the width of GRASS monitor, see also GRASS_HEIGHT

GRASS_WISH
[d.m, nviz]
set wish shell name to override 'wish'

List of selected GRASS variables

[ Use g.gisenv to set/unset/change them ]

DEBUG
[entire GRASS]
sets level of debug message output (0: no debug messages)
g.gisenv set=DEBUG=0

DM_FORM_MODE
[d.m]
sets default form mode (txt or gui)
g.gisenv set=DM_FORM_MODE=txt

GISDBASE
initial database

GIS_LOCK
lock ID to prevent parallel GRASS use,
process id of the start-up shell script

GRASS_DB_ENCODING
[d.what.vect/forms library]
encoding of query form (utf-8, ascii, iso8859-1, koi8-r)

GRASS_GUI
either "text" or "tcltk" to define non-/graphical startup

LOCATION
full path to location directory

LOCATION_NAME
initial location name

MAPSET
initial mapset

OVERWRITE
[all modules]
toggles map overwrite.
With 0 maps are protected (default),
With 1 maps with identical names will be overwritten.
You can force a protected overwrite by adding "--o" to the command.
e.g.:
g.gisenv set="OVERWRITE=0"

GRASS-related Files

$HOME/.grassrc6
stores the GRASS variables (but not environment variables)

$HOME/GIS_ERROR_LOG
If this file exists, all GRASS error messages are stored here instead of sending a mail to the GIS user. To generate the file, use:
touch $HOME/GIS_ERROR_LOG