v.area:

usage: v.area map=vector file name color=color (default is red)

  program first calls d.vect to display map. 

  then, user can use mouse to select area on map bu clicking within the 
  desired area.  Area selected will be highlighted in selected color
  on graphics display.  On regular screen area measurements will be
  displayed, in square meters, hectares, acres, and sq. miles,  Perimeter 
  measurements, in meters, feet, and miles, are also displayed. 
  
  User can repeatedly select areas for analysis, one at a time.
