fsset is a simple program to maintain a database of sets on disk. Each set is
simply a directory on disk. Adding an element to a set is a 'touch' operation.
Removing an element from a set is an 'unlink' operation.

fsset uses a simple protocol and communicates over stdin/stdout. This works well
when paired with djb's tcpserver program (part of his ucspi-tcp package,
available at http://cr.yp.to/ucspi-tcp.html). The protocol is line-based and
should be straightforward - see the library in the fssetpy/ subdirectory for a
sample client implementation.