Some short examples:

open.c --  open a database
phrase.c -- take a phrase and produce all the matches
getfile.c -- take a file identifier and get the file

addfile.c -- add the contents of a file to an index
grep.c -- print the text that was matched
stem.c -- take a word and produce the `canonical reduced form'

Key Value Databases
dbstore.c -- store something in a Key Value Database
dbfetch.c -- fetch something previously stored in a Key Value Database

