Ledger is a powerful, double-entry accounting system that is accessed
from the UNIX command-line. This may put off some users, since there is
no flashy UI, but for those who want unparalleled reporting access to
their data there are few alternatives.

Ledger uses text files for input. It reads the files and generates
reports; there is no other database or stored state. To use Ledger, you
create a file of your account names and transactions, run from the
command line with some options to specify input and requested reports,
and get output. The output is generally plain text, though you could
generate a graph or html instead. Ledger is simple in concept,
surprisingly rich in ability, and easy to use.