Ubuntu Manpage: There are two types of variables:

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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/.grass7/bashrc

           •   To  get  personal  CSH  shell definitions (aliases, color listing option, ...)  into GRASS, store
               them in:
               $HOME/.grass7/cshrc

Setting GRASS gisenv variables

       Use g.gisenv within GRASS. This permanently predefines GRASS variables in the $HOME/.grass7/rc file 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/.grass7/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/.grass7/addons,
on MS Windows $APPDATA\GRASS7\addons.

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

GRASS_BATCH_JOB
defines the name (path) of a shell script to be processed as batch job.

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_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

       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