I am running a shell script for batch processing in GRASS 7 (calling it with sh [...sh] in the command line window), which creates a series of rasters through classifications, raster calculator and regression analysis. What I would like to do now is extend that script, so that it calculates the surface roughness of the resulting raster. r.roughness only works so far in GRASS 6, however. I have GRASS 6 installed as well.
Is it possible to call GRASS 6 and its extensions with the GRASS 7 command line without starting GRASS 6 or do I have to write a script that calls both programs from outside of either GRASS environments?