C toolkits for text search/indexing on UNIX?

[Brian Lawrence Dear]

Anyone know if a C function library or programmer's toolkit that
enables you to add text search/retrieval/indexing capabilities to
your own programs?  I am in desperate need of such a toolkit.
 
I know of one commercial product, Ful/Text from Fulcrum Technologies.
They charge $44,000 for it and that's too much.

If anyone has *ANY* suggestions, please forward them a.s.a.p.
to: brian at coconut.com

Thanks in advance!!!