Ubuntu Manpage: There are two types of variables:

GRASS variables and environment variables

       There are two types of variables:

           •   shell environment variables,

           •   GRASS gisenv variables.
       There are a number of shell environment variable groups:

           •   variables for rendering

           •   variables for internal use
       Note:  Any  setting which needs to be modifiable by a GRASS module (e.g. MONITOR by d.mon)
       has to be a GRASS gisenv variable.

Setting shell environment variables

       Setting shell environment variables depends on the shell being used:
       Bash:
       export VARIABLE=value
       Csh:
       setenv VARIABLE value
       Cmd.exe (Windows):
       set VARIABLE=value
       To set up shell environment variables permanently:

           •   To get personal BASH shell definitions (aliases, color listing option, ...)   into
               GRASS, store them in:
               $HOME/.grass8/bashrc

           •   To  get  personal CSH shell definitions (aliases, color listing option, ...)  into
               GRASS, store them in:
               $HOME/.grass8/cshrc

Setting GRASS gisenv variables

       Use  g.gisenv  within  GRASS.  This  permanently  predefines  GRASS   variables   in   the
       $HOME/.grass8/rc  file  (Linux, Mac, BSD, ...)  or in the %APPDATA%\Roaming\GRASS8\rc file
       (Windows) after the current GRASS session is closed.
       Usage:
       g.gisenv set="VARIABLE=VALUE"
       It looks unusual with two equals signs, but g.gisenv serves  dual  duty  for  getting  and
       setting GRASS variables.

       If the user just specifies a variable name, it defaults to get mode.  For example:
       g.gisenv MAPSET
       PERMANENT

List of selected (GRASS related) shell environment variables

[ To be set from the terminal shell or startup scripts ]

GISBASE
directory where GRASS lives. This is set automatically by the startup script.

GISRC
name of $HOME/.grass8/rc file. Defines the system wide value when starting a GRASS
session. Within a GRASS session, a temporary copy of this file will be used.

GRASS_ADDON_PATH
[grass startup script, g.extension]
specifies additional path(s) containing local and/or custom GRASS modules extra to the
standard distribution.

GRASS_ADDON_BASE
[grass startup script]
allows specifying additional GISBASE for local GRASS modules (normally installed as
GRASS Addons by g.extension module) extra to standard distribution. The default on
GNU/Linux is $HOME/.grass8/addons, on MS Windows %APPDATA%\Roaming\GRASS8\addons.

GRASS_ADDON_ETC
[libgis, g.findetc]
specify paths where support files (etc/) may be found external to standard
distribution.

GRASS_COMPRESSOR
[libraster]
the compression method for new raster maps can be set with the environment variable
GRASS_COMPRESSOR. Supported methods are RLE, ZLIB, LZ4, BZIP2, and ZSTD. The default
is ZSTD if available, otherwise ZLIB, which can be changed with e.g.
GRASS_COMPRESSOR=ZSTD, granted that GRASS has been compiled with the requested
compressor. Compressors that are always available are RLE, ZLIB, and LZ4. The
compressors BZIP2 and ZSTD must be enabled when configuring GRASS for compilation.

GRASS_DB_ENCODING
[various modules, wxGUI]
encoding for vector attribute data (utf-8, ascii, iso8859-1, koi8-r)

GIS_ERROR_LOG
If set, GIS_ERROR_LOG should be the absolute path to the log file (a relative path
will be interpreted relative to the process’ cwd, not the cwd at the point the user
set the variable). If not set, $HOME/GIS_ERROR_LOG is used instead. The file will only
be used if it already exists.

GRASS_ERROR_MAIL
set to any value to send user mail on an error or warning that happens while stderr is
being redirected.

GRASS_FONT
[display drivers]
specifies the font as either the name of a font from $GISBASE/etc/fontcap (or
alternative fontcap file specified by GRASS_FONT_CAP), or alternatively the full path
to a FreeType font file.

GRASS_ENCODING
[display drivers]
the encoding to be assumed for text which is drawn using a freetype font; may be any
encoding know to iconv.

GRASS_FONT_CAP
[g.mkfontcap, d.font, display drivers]
specifies an alternative location (to $GISBASE/etc/fontcap) for the font configuration
file.

GRASS_FULL_OPTION_NAMES
[parser]
Generates a warning if GRASS_FULL_OPTION_NAMES is set (to anything) and a found string
is not an exact match for the given string.

GRASS_GUI
either text (text user interface), gtext (text user interface with GUI welcome
screen), or gui (graphical user interface) to define non-/graphical startup. Can also
specify the name of the GUI to use, e.g. wxpython (wxGUI). Also exists as a GRASS
gisenv variable (see below). If this shell variable exists at GRASS startup, it will
determine the GUI used. If it is not defined startup will default to the last GUI
used.

GRASS_HTML_BROWSER
[init.sh, wxgui]
defines name of HTML browser. For most platforms this should be an executable in your
PATH, or the full path to an executable.
Mac OS X runs applications differently from the CLI. Therefore, GRASS_HTML_BROWSER
should be the application’s signature, which is a domain-like name, just reversed,
i.e. com.apple.Safari. To find an application’s signature, type the following in a
Terminal (fill in the path to the application you are interested in, for example:
/Applications/Safari.app):
grep -A 1 "CFBundleIdentifier" /path/to/application.app/Contents/Info.plist
The signature is the <string> following the <key>, without the bracketing <string>
tags.

GRASS_INT_ZLIB
[libraster]
if the environment variable GRASS_INT_ZLIB exists and has the value 0, new compressed
integer (CELL type) raster maps will be compressed using RLE compression.
If the variable doesn’t exist, or the value is non-zero, zlib compression will be used
instead. 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_ZLIB_LEVEL
[libgis]
if the environment variable GRASS_ZLIB_LEVEL exists and its value can be parsed as an
integer, it determines the compression level used when new compressed raster maps are
compressed using zlib compression. This applies to all raster map types (CELL, FCELL,
DCELL).
Valid zlib compression levels are -1 to 9. The GRASS_ZLIB_LEVEL=-1 corresponds to the
zlib default value (equivalent to GRASS_ZLIB_LEVEL=6). Often GRASS_ZLIB_LEVEL=1 gives
the best compromise between speed and compression.
If the variable doesn’t exist, or the value cannot be parsed as an integer, zlib’s
default compression level 6 will be used.

GRASS_MESSAGE_FORMAT
[various modules, wxGUI]
it may be set to either

• standard - sets percentage output and message formatting style to standard
formatting,

• gui - sets percentage output and message formatting style to GUI formatting,

• silent - disables percentage output and error messages,

• plain - sets percentage output and message formatting style to ASCII output
without rewinding control characters.

GRASS_MOUSE_BUTTON
[various modules]
swaps mouse buttons for two-button or left-handed mice. Its value has three digits 1,
2, and 3, which represent default left, middle, and right buttons respectively.
Setting to 132 will swap middle and right buttons. Note that this variable should be
set before a display driver is initialized (e.g., d.mon x0).

GRASS_PAGER
[various modules]
it may be set to either less, more, or cat.

GRASS_PERL
[used during install process for generating man pages]
set Perl with path.

GRASS_PROXY
[used during addon install/reinstall process for generating man pages (download commit
from GitHub API server and remote modules.xml file)]
set the proxy with: GRASS_PROXY="http=<value>,ftp=<value>".

GRASS_SKIP_MAPSET_OWNER_CHECK
By default it is not possible to work with MAPSETs that are not owned by current user.
Setting this variable to any non-empty value allows the check to be skipped.

GRASS_SH
[shell scripts on Windows]
path to bourne shell interpreter used to run shell scripts.

GRASS_SIGSEGV_ON_ERROR
Raise SIGSEGV if an error occurs]
This variable can be set for debugging purpose. The call of G_fatal_error() will end
in a segmentation violation. GDB can be used to trace the source of the error.

GRASS_PYTHON
[wxGUI, Python Ctypes]
set to override Python executable.
On Mac OS X this should be the pythonw executable for the wxGUI to work.

GRASS_VECTOR_LOWMEM
[vectorlib]
If the environment variable GRASS_VECTOR_LOWMEM exists, memory consumption will be
reduced when building vector topology support structures. Recommended for creating
large vectors.

GRASS_VECTOR_OGR
[vectorlib, v.external.out]
If the environment variable GRASS_VECTOR_OGR exists and vector output format defined
by v.external.out is PostgreSQL, vector data is written by OGR data provider even the
native PostGIS data provider is available.

GRASS_VECTOR_EXTERNAL_IMMEDIATE
[vectorlib, v.external.out]
If the environment variable GRASS_VECTOR_EXTERNAL_IMMEDIATE exists and vector output
format defined by v.external.out is non-native, vector features are written to output
external datasource immediately. By default, the vector library writes output data to
a temporary vector map in native format and when closing the map, the features are
transferred to output external datasource. Note: if output vector format is
topological PostGIS format, then the vector library writes features immediately to
output database (in this case GRASS_VECTOR_EXTERNAL_IMMEDIATE is ignored).

GRASS_VECTOR_EXTERNAL_IGNORE
[vectorlib]
If the environment variable GRASS_VECTOR_EXTERNAL_IGNORE exists, output vector format
defined by v.external.out is ignored. The format is always native.

GRASS_VECTOR_TEMPORARY
[vectorlib]
If the environment variable GRASS_VECTOR_TEMPORARY exists, GRASS vector library will
operate on temporary vector maps. New vector maps will be created in temporary
directory (see GRASS_VECTOR_TMPDIR_MAPSET variable), existing vector maps will be read
(if found) also from this directory. It may be set to either:

• keep - the temporary vector map is not deleted when closing the map.

• move - the temporary vector map is moved to the current mapset when closing the
map.

• delete - the temporary vector map is deleted when closing the map.
Default value is keep. Note that temporary vector maps are not visible to the user via
g.list or wxGUI. They are used internally by the GRASS modules and deleted automatically
when GRASS session is quited.

GRASS_VECTOR_TMPDIR_MAPSET
[vectorlib]
By default GRASS temporary directory is located in $LOCATION/$MAPSET/.tmp/$HOSTNAME.
If GRASS_VECTOR_TMPDIR_MAPSET is set to ’0’, the temporary directory is located in
TMPDIR (environmental variable defined by the user or GRASS initialization script if
not given).
Important note: This variable is currently used only in vector library. In other words
the variable is ignored by raster or raster3d library.

GRASS_VECTOR_TOPO_DEBUG
[vectorlib, v.generalize]
If the environment variable GRASS_VECTOR_TOPO_DEBUG exists, v.generalize runs in
extremely slow debug mode.

GRASS_WXBUNDLED
[wxGUI]
set to tell wxGUI that a bundled wxPython will be used.
When set, the wxGUI will not check the wxPython version, as this function is
incompatible with a bundled wxPython. It is up to the packager to make sure that a
compatible wxPython version is bundled.

GRASS_WXVERSION
[wxGUI]
set to tell wxGUI which version of wxPython to use.
When set, the wxGUI will select the given wxPython version. It’s useful when multiple
versions of wxPython are installed and the user wants to run wxGUI with non-default
wxPython version.

GRASS_XTERM
[lib/init/grass-xterm-wrapper, lib/init/grass-xterm-mac]
set to any value (e.g. rxvt, aterm, gnome-terminal, konsole) to substitute
’x-terminal-emulator’ or ’xterm’. The Mac OS X app startup defaults to an internal
’$GISBASE/etc/grass-xterm-mac’, which emulates the necessary xterm functionality in
Terminal.app.

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_NO_GLX_PBUFFERS
[nviz]
set to any value to disable the use of GLX Pbuffers.

GRASS_NO_GLX_PIXMAPS
[nviz]
Set to any value to disable the use of GLX Pixmaps.

OMP_NUM_THREADS
[OpenMP]
If OpenMP support is enabled this limits the number of threads. The default is set to
the number of CPUs on the system. Setting to ’1’ effectively disables parallel
processing.

TMPDIR, TEMP, TMP
[Various GRASS GIS commands and wxGUI]
The default wxGUI temporary directory is chosen from a platform-dependent list, but
the user can control the selection of this directory by setting one of the TMPDIR,
TEMP or TMP environment variables Hence the wxGUI uses $TMPDIR if it is set, then
$TEMP, otherwise /tmp.

List of selected GRASS environment variables for rendering
[ In addition to those which are understood by specific GRASS display drivers, the
following variables affect rendering. ]

GRASS_RENDER_IMMEDIATE
tells the display library which driver to use; possible values: cairo, png, ps, html
or default.
Default display driver is cairo (if available) otherwise png.

GRASS_RENDER_WIDTH
defines the width of output image (default is 640).

GRASS_RENDER_HEIGHT
defines the height of output image (default is 480).

GRASS_RENDER_FILE
the name of the resulting image file.

GRASS_RENDER_FRAME
contains 4 coordinates, top,bottom,left,right (pixel values) with respect to the top
left corner of the output image, defining the initial frame.

GRASS_RENDER_LINE_WIDTH
defines default line width.

GRASS_RENDER_TEXT_SIZE
defines default text size.

GRASS_RENDER_COMMAND
external command called by display library to render data (see example in display
drivers page for details).
Currently only Python scripts are supported. For specific driver-related variables
see:

• Cairo display driver

• PNG display driver

• PS (Postscript) display driver

• HTML display driver

List of selected internal GRASS environment variables
[ These variables are intended for internal use only by the GRASS software to facilitate
communication between the GIS engine, GRASS scripts, and the GUI. The user should not set
these in a GRASS session. They are meant to be set locally for specific commands. ]

GRASS_OVERWRITE
[all modules]
toggles map overwrite.

• 0 - maps are protected (default),

• 1 - maps with identical names will be overwritten.
This variable is automatically created by g.parser so that the --overwrite option will be
inherited by dependent modules as the script runs. Setting either the GRASS_OVERWRITE
environment variable or the OVERWRITE gisenv variable detailed below will cause maps with
identical names to be overwritten.

GRASS_VERBOSE
[all modules]
toggles verbosity level

• -1 - complete silence (also errors and warnings are discarded)

• 0 - only errors and warnings are printed

• 1 - progress and important messages are printed (percent complete)

• 2 - all module messages are printed

• 3 - additional verbose messages are printed
This variable is automatically created by g.parser so that the --verbose or --quiet flags
will be inherited by dependent modules as the script runs.

GRASS_REGION
[libgis]
override region settings, separate parameters with a ";". Format is the same as in the
WIND region settings file. Otherwise use is the same as WIND_OVERRIDE.

WIND_OVERRIDE
[libgis]
it causes programs to use the specified named region (created with e.g. g.region
save=...) to be used as the current region, instead of the region from the WIND file.
This allows programs such as the GUI to run external commands on an alternate region
without having to modify the WIND file then change it back afterwards.

List of selected GRASS gisenv variables

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

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

       WX_DEBUG
           [wxGUI]
           sets level of debug message output for wxGUI (0: no debug messages, 1-5 debug levels)

       GISDBASE
           initial database

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

       GUI
           See GRASS_GUI environmental variable for details.

       LOCATION
           full path to location directory

       LOCATION_NAME
           initial location name

       MAPSET
           initial mapset

       MEMORYMB
           [entire GRASS with focus on raster related data processing]
           sets the maximum memory to be used (in MB), i.e. the cache size for raster rows
           # set to 6 GB (default: 300 MB)
           g.gisenv set="MEMORYMB=6000"

       NPROCS
           sets the number of threads for parallel computing
           # set to use 12 threads (default: 1)
           g.gisenv set="NPROCS=12"

       OVERWRITE
           [all modules]
           toggles map overwrite.

           •   0 - maps are protected (default),

           •   1 - maps with identical names will be overwritten.
       This  variable is automatically created by g.parser so that the --overwrite option will be
       inherited by dependent modules as the script  runs.  Setting  either  the  GRASS_OVERWRITE
       environment  variable or the OVERWRITE gisenv variable detailed below will cause maps with
       identical names to be overwritten.

GRASS-related Files