[GRASS-dev] Re: 'g.gui wxpython' won't work in wingrass as
wxgui is a shell script
ivan at theory.asu.ru
Thu Feb 28 23:03:49 EST 2008
>>>>> Michael Barton <michael.barton at asu.edu> writes:
>> It may be a stupid question, but what scripting language is
>> proposed to replace POSIX Shell in GRASS? The GRASS environment
>> seems to benefit a lot from relying on a Shell-like language.
>> E. g., I could hardly imagine using any language other than Shell
>> for the following:
>> $ g.mlist type=rast pattern=2008-\*-temperature \
>> (while read r ; do
>> s="$r"-celsius ; r.mapcalc "\"$s\" = \"$r\" - 273.15" ; \
>> (Surely, there's an Olin Shivers et al work [1, 2], but it seems to
>> me that Shell is a bit easier to explain to a non-programmer than
>> Scheme [3, 4].)
>>  http://www.scsh.net/
>>  http://www.scsh.net/resources/commander-s.html
>>  http://www.r6rs.org/
>>  http://www.schemers.org/
> For the foreseeable future, Linux/Unix systems will continue to have
> a shell available to do the operation in your example. One of the
> important features of GRASS is that many operations can be performed
> in a variety of scripting environments--including bash or other
> However, Windows does not have a shell. If GRASS is to be truly
> cross- platform, then all basic GRASS functions need to operate on
> all supported platforms. This poses a significant problem for Windows
> users. Cygwin has been quite difficult to install for most users,
> very difficult to use in a shared classroom/lab setting, and (in my
> experience) somewhat unstable. There is now a 'native' Windows build
> of GRASS, but it requires custom hacks for bash scripts and other
> bashisms common in GRASS
As Bash becomes somewhat less popular in the GNU world and being
replaced by other POSIX-compatible Shells, it makes sense to get
rid of bashisms irrespective of the platform.
> --and installing msys--and these have been the most problematic part
> of running GRASS in Windows so far.
Strangely enough, I had no troubles installing Msys recently
(along with Tcl & Tk I've cross-compiled for W32.)
> Also, many users are not particularly comfortable with arcane bash
> shell commands--like in your example above--although I know others
> who have a special fondness for bash.
> The current plan is ultimately for all core GRASS functions to run as
> binaries in a cross-platform compiled language (C for most things) OR
> in Python as a cross-platform scripting environment for GUI and
> 'permanent' scripts (i.e., those that are distributed as part of
> GRASS). I'm not familiar with Olin Shivers; I've heard of Scheme, but
> don't know it.
The point is that Scsh, designed by Olin Shivers, employs a
special Shell-like notation for running external commands. I
don't know any other language to implement such a feature.
> However, IMHO, Python is much easier to teach someone and to work
> with than bash.
Well, I've heard of Python, but don't know it. Could you please
show me the ``g.mlist ...'' fragment above rewritten in Python?
> Nevertheless, for those on *nix systems, bash will continue to be a
> scripting platform for GRASS into the near future.
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