[GRASS-dev] r.mapcalc and g.remove --v/q issues

Maciej Sieczka tutey at o2.pl
Tue Oct 10 12:49:49 EDT 2006

Glynn Clements wrote:
> Sören Gebbert wrote:
>> i just tested g.remove (lates grass cvs version).
>> If i try to remove a non existent map i get this warning:
>> GRASS 6.3.cvs > g.remove rast=huch
>> WARNING: <huch> nothing removed
>> I think this is a wrong warning, because map "huch" does not exist.
>> Maybe i'm doing something wrong?
> So far as g.remove is concerned, maps don't "exist" (or not) as
> monolithic entities. A map (or any other entity type, e.g. stored
> regions) can have multiple elements; e.g. a raster map can have any or
> all of the elements:
> 	cell cellhd cats colr hist cell_misc fcell g3dcell
> Previously, g.remove would simply tell you whether the element was
> removed, missing, or removal failed. If a map didn't exist at all, it
> would just print "MISSING" for every element.
> Now, it prints nothing if one or more elements exist, and the above
> warning if no elements exist.
> The basic behaviour is correct, but we might want to think about the
> exact message. The above might be interpreted as meaning that
> something which exists wasn't removed, when it actually signifies that
> nothing was removed, either because there wasn't anything to remove or
> because removal failed.
> Note that if an element exists but removal fails, you get a separate
> warning for each failed removal.

Still g.remove doesn't output an information like it should,
considering it's function, for either the success or failure case.
Here's why I think so:

There is a thing called raster map in GRASS, so the 'g.remove rast=map'
should be concerned with this thing as a whole. Same for g.copy/rename,
 It's not the point whether a raster map is consisted of one or more
and what kind of files actually. There is no need to pull the user into
the details of the GRASS raster format in any of these modules at a
default DEBUG level. So the message should just be "WARNING: raster map
<huch> not found" for failure and "raster map <huch> removed" for
successs. It should not refer to particular components *directly*, like
it used to until recently, or *indirectly*, like it does now in
"WARNING: <huch> nothing removed". For the latter I mean that the
"nothing" implies that "something" would be removed under some
circumstances, and "something" would not - like if a raster map was not
an integral unity (again, it doesn't matter raster im GRASS is made of
a few files; they are only a form for the content that the raster is).
A module to remove a map is not supposed to be concerned with the
internals of the given map. It is just supposed to try to remove the
map, return a failure or success and issue appropriate information if
failed or succeeded.


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