[GRASSLIST:4468] using v.what.rast

[Joel Peter William Pitt]

Hi All,

I'm trying to use v.what.rast to find out the value of cells in a raster
map at the coordinates of shapes in a vector file (using grass5.7 cvs)

A couple of problems I'm having are:
1. How do I create a new column in a table within a dbf file? Is it
possible through GRASS? Or should I just use a seperate tool?
2. I've tried just overwriting the category( "cat" ) column but nothing 
happens:

1284 categories loaded from table
0 categories loaded from vector
0 categories from vector missing in table
0 duplicate categories in vector
0 records updated
0 update errors

Is this because v.what.rast is limited to only points? If so, can anyone
suggest a way of either converting shapes to sets of points, or calculating
the number of cells of each type under a shape?

Thanks for your time,

Joel