Take a look at the sample files in spearfish/PERMANENT/dig_cats.
If you do not have a copy of the spearfish data, you can download them
from moon.cecer.army.mil or send a note to me and I will mail you a
sample dig_cats file.
I have been having similar problem knowing exactly what format GRASS4.0
expects different files to be in. Sample files are fine, explicit descriptors
like those found in the DLG Data User's Guides that explain every record and the
format of every field would be excellent.