[GRASS-user] Silent commands in python

[Daniel Victoria]

Thanks all,

I'll check the subprocess module. Sounds interesting and a lot more
complete then os.system. I'll just have to study a bit more... Those
are the problems of being a self thought hacker with no formal
programing education :)

Cheers
Daniel

On Dec 4, 2007 7:40 AM, Hamish <hamish_nospam at yahoo.com> wrote:
>
> Daniel Victoria wrote:
> > This might be more of a python problem but here it goes...
> > I wrote a water balance script in python to run under GRASS. What I
> > would like now is that the commands in the python script would be
> > silent, that is, no return from stdout or stderr.
> > For instance every time I call a r.mapcalc function I get the 0-100%
> > count. I'd like to silence that and other commands.
> >
> > In the shell I would silence command outputs using &> /dev/null, for exemple:
> > echo "blabla=2*bla" | r.mapcalc &> /dev/null
> >
> > But in python that does not work using the os.system() function, that is:
> > os.system("echo 'blabla=2*bla' | r.mapcalc &> /dev/null")
> >
> > Anyone has any tips on the matter?
>
>
> If this is purely for cosmetic/usability reasons*, and not for technical ones**
>  you've got some options in GRASS 6.3.
>
> *  (hard to see the important messages with all the noise)
> ** (like tcl's anything to stderr is an error)
>
>
> The easiest is to pass the --quiet flag on the module command line. This works
> for almost all modules. The big exception to that is r.mapcalc which doesn't
> use the standard parser.
>
> For r.mapcalc, or if you want to set a blanket --quiet directive for the whole
> script, you can set the GRASS_VERBOSE environmental variable. Python's os
> module has a putenv() function to do that.
>
> These are the levels you can use:
>   (from lib/gis/verbose.c)
> 0 - module should print nothing but errors and warnings (G_fatal_error,
>       G_warning)  Triggered by "--q" or "--quiet".
> 1 - module will print progress information (G_percent)
> 2 - module will print all messages (G_message)  [default level]
> 3 - module will be very verbose. Triggered by "--v" or "--verbose".
>
> "--quiet" will set the level to 0.
>
>
> shell script example
> # for everything that follows
> GRASS_VERBOSE=1
> export GRASS_VEBOSE
>
> # override for just one module
> GRASS_VERBOSE=0 \
>   r.mapcalc "only_set = for_this_process"
>
>
> Another nice thing about using the enviro variable method is that it is
> silently ignored for earlier versions of GRASS. For earlier versions of GRASS
> an error happens when "--quiet" isn't recognized as a valid command line
> option. (the new 6.2.3 knows to ignore it)
>
>
> see "Verbosity levels" at
>   http://grass.gdf-hannover.de/wiki/Development_Specs
>
>
> The advantage of these methods versus sending all stderr to /dev/null is that
> warning and error messages are not lost, making prototyping and debugging a
> whole lot easier.
>
>
> Hamish
>
>
>
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