[GRASS-user] How to add calculated length data to new colum

[SGW00412 at nifty.com]

I want to add calculated data to vector file.

for example, I have vector file (sample_overlay).

v.report map=sample_overlay option=length

cat|a_cat|a_HIGHT|b_cat|b_row|b_col|length
1|11|L|1473|30|23|1|21.3047451513242
2|12|H|1829|37|29|2|19.9524518420696

I want to add this length data to sample_overlay.

So, I tried to add new colum to sample_overlay.

v.db.addcol sample_overlay columns="length double precision"

How to add this length data to new colum of sample_overlay?

Shimada