How to incorporate exec sql describe select list ( available in sql server in postgres)

Hi,
I have requirement where for a select statement i need dbms column 
information like data type,precision,scale, length etc
In Oracle using "exec sql describe select list ..." it is possible 
to obtain the above information. In postgres descriptor is 
avaialble only after fetching from the cursor. This is not 
possbile through ecpg programming. But i was thinking whether it 
is possible to do with libpq programming. If so can anyone send me 
pointer to the code.

Regards
Prashanth Kamath