[GRASS-user] can I access mapset outside of grass, by using python?

[Glynn Clements]

Milton Cezar Ribeiro wrote:

> I can run some simple scripts on python if I start
> Msys -> grass64 -> python myscrypt.py
> 
> But now I would like to know if I can build a python
> code outside of a msys/grass session, and get
> access on a mapset withour stay running grass.

The GRASS libraries require certain environment variables to be set. A
"GRASS session" is just a set of processes (e.g. a shell and/or GUI)
which have the necessary environment settings.

Specifically:

GISBASE needs to be set to the top-level directory of the GRASS
installation.

GISRC needs to contain the absolute path to a file containing settings
for GISDBASE, LOCATION_NAME and MAPSET.

PATH needs to include $GISBASE/bin and $GISBASE/scripts.

If the GRASS libraries are shared libraries, the loader needs to be
able to find them. This normally means that LD_LIBRARY_PATH (Linux,
Solaris), DYLD_LIBRARY_PATH (MacOSX) or PATH (Windows) need to contain
$GISBASE/lib, although there are other means to the same end (e.g. on
Linux, putting $GISBASE/lib (with $GISBASE replaced by its actual
value) into /etc/ld.so.conf then running ldconfig).

Some libraries and modules use other variables. See the file
$GISBASE/docs/html/variables.html for most of them (the display
libraries used by d.* commands use additional variables, which are
documented along with the individual drivers).

Personally, I have the following run from my ~/.bash_profile script:

	export GISBASE=/usr/local/src/grass/svn/dist.i686-pc-linux-gnu
	export GRASS_GNUPLOT='gnuplot -persist'
	export GRASS_WIDTH=640
	export GRASS_HEIGHT=480
	export GRASS_HTML_BROWSER=firefox
	export GRASS_PAGER=cat
	export GRASS_WISH=wish
	export GRASS_PYTHON=python
	export GRASS_MESSAGE_FORMAT=silent
	export GRASS_TRUECOLOR=TRUE
	export GRASS_TRANSPARENT=TRUE
	export GRASS_PNG_AUTO_WRITE=TRUE
	
	export PATH="$GISBASE/bin:$GISBASE/scripts:$PATH"
	export LD_LIBRARY_PATH="$GISBASE/lib"
	export GRASS_LD_LIBRARY_PATH="$LD_LIBRARY_PATH"
	export PYTHONPATH="$GISBASE/etc/python:$PYTHONPATH"
	export MANPATH=$MANPATH:$GISBASE/man
	
	export GIS_LOCK=$$
	export GRASS_VERSION="7.0.svn"
	
	tmp=/tmp/grass6-"`whoami`"-$GIS_LOCK
	export GISRC="$tmp/gisrc"
	mkdir "$tmp"
	cp ~/.grassrc6 "$GISRC"

This allows GRASS commands to be used anywhere (my ~/.Xsession sources
the bash startup scripts, so the settings aren't limited to
interactive shells, but also work for e.g. M-! in XEmacs). Each
interactive shell gets a separate "session" (i.e. a separate $GISRC
file), while GUI programs share a common session.

The above is for GRASS 7, and uses the version from the dist.<arch>
directory in the GRASS source tree rather than an installed version.

The only time I ever start GRASS explicitly is if I need to test
changes to the startup scripts, or test a 6.x version.

-- 
Glynn Clements <glynn at gclements.plus.com>