[GRASS-user] scripting mapcalc

[achim]

Hi,

did someone tried -like me- to use r.mapcalc in a script inside an
do-while-clause?

I cannot pass changing variables $old, $new like:
r.mapcalc 'river=if(river=$old,$new,null())'
its because of the '', which are needed because if the if-statement.
I failed passing the hole statement eg. 'river=if(river=5,4,null())' as
a variable like:
r.mapcac $statement
...

I tried many things and some shells (bash,csh,tcsh)...

I think its because the ''. Besides when it seemed do be expressed the
right way I got this answer:

r.mapcalc 'river=if(river=4032076,4032075,null())' <-debugging output
syntax error, unexpected $end, expecting '='
Parse error

or

syntax error, unexpected '=', expecting ')'
Parse error

or

Ungültiger Dateiname. Das Zeichen <=> ist nicht erlaubt.
Ungültige Karte <if(river=4032076,4032075,null())>
Parse error

depending on what I tried.

Can someone help?

Or is there another (and faster) way to query raster-data without
writing a C-Program?

I'd like to do it inside grass. Otherwise I would export the map to
octave to calculate there, but its not the gentle way I think.

Thanks,
achim