[GRASSLIST:3984] how to access built-in vector attributes (GRASS 5.7)?

Or whatever they're called.  Right now I'm looking at lines.  When you 
d.what.vect, it shows cats, fields and attributes, and length and line 
height.  I haven't checked polgons yet, but I'm guessing they have 
perimeter and area instead of length.

1. I would like to v.extract to extract lines above a certain length - 
ie weed out those short blips.

2. I want to export the lines with line height as an attribute.  Not 
important now, but labelling lines with line height, using different 
colors... (not ready to mess with NVIZ yet, but maybe that's the only 
way?), or extracting certain line heights or ranges of heights.


I couldn't find any info on these 'attributes' - so I'm sot sure if 
they are something that can be queried or not.

-----
William Kyngesburye <kyngchaos@xxxxxxxxxxx>
http://webpages.charter.net/kyngchaos/

"Time is an illusion - lunchtime doubly so."

- Ford Prefect