[GRASSLIST:8174] Cut a polygon (Area/boudary) into two?

[Phillip J. Allen]

Hi all,

I have an area vector layer and a want to draw a line across it and cut 
it into two sperate polygons.  How do I do this? 

I know it's a silly question but must say that I amost exclusively have 
only ever used Grass for raster manaipulations.  I normaly use ArcGis 
for vectors.  Now that Grass has the new vector format I think I might 
be able to get more use from it with vectors.

thanks,

Phil