GRASS startup program

SYNOPSIS
- Flags:
- Parameters:
DESCRIPTION
- Running non-interactive jobs
- Config flag
SAMPLE DATA
ENVIRONMENT VARIABLES
EXAMPLES
- Batch jobs with the exec interface
CAVEAT
SEE ALSO
AUTHORS (of this page)

SYNOPSIS

grass [-h | -help | --help] [-v | --version] | [-c | -c geofile | -c EPSG:code[:datum_trans]] | -e | -f | [--text | --gtext | --gui] | --config | [--tmp-location | --tmp-mapset] [[[<GISDBASE>/]<LOCATION>/] <MAPSET>] [--exec EXECUTABLE]

Flags:

-h | -help | --help: Prints a brief usage message and exits
-v | --version: Prints the version of GRASS and exits
-c: Creates new GRASS unprojected location in specified GISDBASE
-c geofile: Creates new GRASS projected location in specified GISDBASE based on georeferenced file
-c EPSG:code: Creates new GRASS projected location in specified GISDBASE with given EPSG code
-c EPSG:code:datum_trans: Creates new GRASS projected location in specified GISDBASE with given EPSG code and datum transform parameters
-e: Exit after creation of location or mapset. Only with -c flag
-f: Forces removal of .gislock if exists (use with care!). Only with --text flag
--text: Indicates that Text-based User Interface should be used (skip welcome screen)
--gtext: Indicates that Text-based User Interface should be used (show welcome screen)
--gui: Indicates that Graphical User Interface (wxGUI) should be used
--config: Prints GRASS configuration parameters (options: arch, build, compiler, date, path, python_path, revision, svn_revision, version)
--exec EXECUTABLE: Execute GRASS module or script. The provided executable will be executed in a GRASS GIS non-interactive session.
--tmp-location: Run using a temporary location which is created based on the given coordinate reference system and deleted at the end of the execution (use with the --exec flag). The active mapset will be the PERMANENT mapset.
--tmp-mapset: Run using a temporary mapset which is created in the specified location and deleted at the end of the execution (use with the --exec flag).

Parameters:

GISDBASE: Initial database directory which should be a fully qualified path (e.g., /usr/local/share/grassdata)
LOCATION: Initial location directory which is a subdirectory of GISDBASE
MAPSET: Initial mapset directory which is a subdirectory of LOCATION

Note: These parameters must be specified in one of the following ways:

    MAPSET
    LOCATION/MAPSET
    GISDBASE/LOCATION/MAPSET

DESCRIPTION

This command is used to launch GRASS GIS. It will parse the command line arguments and then initialize GRASS for the user. Since GRASS modules require a specific environment, this program must be called before any other GRASS module can run. The command line arguments are optional and provide the user with a method to indicate the desired user interface, as well as the desired mapset to work on.

The startup program will remember both the desired user interface and mapset. Thus, the next time the user runs GRASS, typing grass (without any options) will start GRASS with the previous settings for the user interface and mapset selected.

If you specify a graphical user interface (--gui) the grass program will try to verify that the system you specified exists and that you can access it successfully. If any of these checks fail then grass will automatically switch back to the text user interface mode.

Running non-interactive jobs

The --exec flag can run an executable on path, GRASS module, or a script. All are executed as a subprocess and any additional arguments are passed to it. A script needs to be specified by full or relative path and on unix-likes systems, the script file must have its executable bit set. Calling the interpreter (e.g., python) and providing the script as a parameter is possible, too. When it is finished GRASS will automatically exit using the return code given by the subprocess. Although the execution itself is non-interactive (no GUI or shell), the subprocess itself can be interactive if that is what the user requires.

Config flag

The flag --config option prints GRASS GIS configuration and version parameters, with the options:

arch: system architecture (e.g., x86_64-pc-linux-gnu)
build: (e.g., ./configure --with-cxx --enable-largefile --with-proj [...])
compiler: (e.g., gcc)
date: (e.g., Tue Mar 31 20:34:57 2020 +0200)
path: (e.g., /usr/lib64/grass)
python_path: (e.g., /usr/lib64/grass/etc/python)
revision: (e.g., 745ee7ec9)
svn_revision: (e.g., 062bffc8)
version: (e.g., 8.2.0dev)

SAMPLE DATA

The GRASS GIS project provides several free sample geospatial datasets as ready-to-use locations. They are available to download at https://grass.osgeo.org/download/sample-data/. The "North Carolina data set" is a modern package of geospatial data from North Carolina (USA), and it includes raster, vector, LiDAR and satellite data. This is the most extensively used data set in the documentation and the examples throughout the user manual pages are based upon it.

ENVIRONMENT VARIABLES

A number of environment variables are available at GRASS startup to assist with automation and customization. Most users will not need to bother with these.

In addition to these shell environment variables GRASS maintains a number of GIS environment variables in the $HOME/.grass8/rc file. User changes to this file will be read during the next startup of GRASS. If this file becomes corrupted the user may edit it by hand or remove it to start afresh. See the list of implemented GRASS variables for more information. The rest of this help page will only consider shell environment variables.

Note that you will need to set these variables using the appropriate method required for the UNIX shell that you use (e.g. in a Bash shell you must export the variables for them to propagate).

User Interface Environment Variable

The grass program will check for the existence of an environment variable called GRASS_GUI which indicates the type of user interface for GRASS to use. If this variable is not set when grass is run, then it will be created and then saved in the $HOME/.grass8/rc file for the next time GRASS is run. It can be set to text, gtext or gui.

There is an order of precedence in the way grass determines the user interface to use. The following is the hierarchy from highest precedence to lowest.

Command line argument
Environment variable GRASS_GUI
Value set in $HOME/.grass8/rc (GUI)
Default value - gui

Python Environment Variables

If you choose to use wxGUI interface, then the GRASS_PYTHON environment variable can be used to override your system default python command.

Suppose for example your system has Python 3.6 installed and you install a personal version of the Python 3.8 binaries under $HOME/bin. You can use the above variables to have GRASS use the Python 3.8 binaries instead.

   GRASS_PYTHON=python3.8

Addon Path to Extra User Scripts

This environment variable allows the user to extend the GRASS program search paths to include locally developed/installed GRASS modules or user scripts.

   GRASS_ADDON_PATH=/usr/mytools
   GRASS_ADDON_PATH=/usr/mytools:/usr/local/othertools

In this example above path(s) would be added to the standard GRASS path environment.

Addon Base for Extra Local GRASS Addon Modules

This environment variable allows the user to extend the GRASS program search paths to include locally installed (see g.extension for details) GRASS Addon modules which are not distributed with the standard GRASS release.

   GRASS_ADDON_BASE=/usr/grass-addons

In this example above path would be added to the standard GRASS path environment.

If not defined by user, this variable is set by GRASS startup program to $HOME/.grass8/addons on GNU/Linux and %APPDATA%\Roaming\GRASS8\addons on MS Windows.

HTML Browser Variable

The GRASS_HTML_BROWSER environment variable allows the user to set the HTML web browser to use for displaying help pages.

EXAMPLES

The following are some examples of how you could start GRASS

grass: Start GRASS using the default user interface. The user will be prompted to choose the appropriate location and mapset.
grass --gui: Start GRASS using the graphical user interface. The user will be prompted to choose the appropriate location and mapset.
grass --text: Start GRASS using the text-based user interface. Appropriate location and mapset must be set by environmental variables (see examples below) otherwise taken from the last GRASS session.
grass --gtext: Start GRASS using the text-based user interface. The user will be prompted to choose the appropriate location and mapset.
grass $HOME/grassdata/spearfish70/user1: Start GRASS using the default user interface and automatically launch into the given mapset, bypassing the mapset selection menu.
grass --gui -: Start GRASS using the graphical user interface and try to obtain the location and mapset from environment variables.
grass -c EPSG:4326 $HOME/grassdata/mylocation: Creates a new GRASS location with EPSG code 4326 (latitude-longitude, WGS84) in the specified GISDBASE
grass -c EPSG:5514:3 $HOME/grassdata/mylocation: Creates a new GRASS location with EPSG code 5514 (S-JTSK / Krovak East North - SJTSK) with datum transformation parameters used in Czech Republic in the specified GISDBASE
grass -c XY $HOME/grassdata/gnomonic --exec g.proj -c proj4='+proj=gnom +lat_0=90 +lon_0=-50': Creates a new GRASS location from PROJ definition string (here: gnomonic) in the specified GISDBASE
grass -c myvector.shp $HOME/grassdata/mylocation: Creates a new GRASS location based on georeferenced Shapefile
grass -c myraster.tif $HOME/grassdata/mylocation: Creates a new GRASS location based on georeferenced GeoTIFF file

Batch jobs with the exec interface

Creating a new Location based on a geodata file's projection (-c) and exit (-e) immediately:

grass -c elevation.tiff -e /path/to/grassdata/test1/

Linking external raster data to PERMANENT Mapset:

grass /path/to/grassdata/test1/PERMANENT/ --exec r.external input=basins.tiff output=basins
grass /path/to/grassdata/test1/PERMANENT/ --exec r.external input=elevation.tiff output=elevation

Get statistics for one raster map:

grass /path/to/grassdata/test1/PERMANENT/ --exec r.univar map=elevation

Compare the rasters visually:

grass /path/to/grassdata/test1/PERMANENT/ --exec g.gui.mapswipe first=elevation second=basins

Execution of shell and Python scripts instead of single commands

A sequence of commands can be bundled in a script and executed using the exec interface.

Shell script example: the command to execute a shell script might be:

grass /path/to/grassdata/test1/PERMANENT/ --exec sh test.sh

A very simple bash script ("test.sh") may look like this:

#!/bin/bash

g.region -p
g.list type=raster
r.info elevation

Python script example: the command to execute a Python script might be:

grass /path/to/grassdata/test1/PERMANENT/ --exec python test.py

A very simple Python script ("test.py") may look like this:

#!/usr/bin/env python3

# import GRASS Python bindings (see also pygrass)
import grass.script as gs

gs.message('Current GRASS GIS environment:')
print(gs.gisenv())

gs.message('Available raster maps:')
for raster in gs.list_strings(type='raster'):
    print(raster)

gs.message('Available vector maps:')
for vector in gs.list_strings(type='vector'):
    print(vector)

Using temporary location

Creating a new temporary location based on a georeferenced file's projection coordinate reference system (CRS) and simultaneously starting computation in a shell script:

grass --tmp-location elevation.tiff --exec test.sh

The same, but using an EPSG code and a Python script:

grass --tmp-location EPSG:3358 --exec test.py

Finally, for special cases, we can create an XY location without any CRS:

grass --tmp-location XY --exec test.py

Temporary location is automatically deleted after computation, so the script is expected to export, link or otherwise preserve the output data before ending.

A single command can be also executed, e.g. to examine properties of the temporary location:

grass --tmp-location EPSG:3358 --exec g.proj -p

A temporary XY location with single command is useful, e.g. to show help text of a module:

grass --tmp-location XY --exec r.neighbors --help

Using temporary mapset

A single command can be executed, e.g., to examine properties of a location (here using the NC SPM sample location):

grass --tmp-mapset /path/to/grassdata/nc_spm_08/ --exec g.proj -p

Computation in a Python script can be executed in the same way:

grass --tmp-mapset /path/to/grassdata/nc_spm_08/ --exec processing.py

Additional parameters are just passed to the script, so we can run the script with different sets of parameters (here 5, 8 and 3, 9) in different temporary mapsets which is good for parallel processing.

grass --tmp-mapset /path/to/grassdata/nc_spm_08/ --exec processing.py 5 8
grass --tmp-mapset /path/to/grassdata/nc_spm_08/ --exec processing.py 3 9

The same applies to Bash scripts (and other scripts supported on you platform):

grass --tmp-mapset /path/to/grassdata/nc_spm_08/ --exec processing.sh 5 8

The temporary mapset is automatically deleted after computation, so the script is expected to export, link or otherwise preserve the output data before ending.

Troubleshooting

Importantly, to avoid an "[Errno 8] Exec format error" there must be a shebang line at the top of the script (like #!/bin/sh, #!/bin/bash, or #!/usr/bin/env python3) indicating which interpreter to be used for the script. The script file must have its executable bit set.

CAVEAT

If you start GRASS using the wxGUI interface you must have a python command in your $PATH variable. That is, the command must be named python and not something like python3.6. Rarely some Python installations do not create a python command. In these cases you can override python by GRASS_PYTHON environmental variable.

Furthermore, if you have more than one version of Python installed, make sure that the version you want to use with GRASS is set by GRASS_PYTHON environmental variable.

AUTHORS (of this page)

Justin Hickey
Markus Neteler
Hamish Bowman
Martin Landa, Czech Technical University in Prague, Czech Republic

Main index | Topics index | Keywords index | Graphical index | Full index