GNU Direvent monitors events in the file system directories. For each
event that occurs in a set of pre-configured directories, the program
calls an external program associated with it, supplying it with the
information about the event and the location within the file system
where it occured.

Interfaces for tracking changes to file systems are highly
system-specific. Direvent aims to provide a uniform and
system-independent command-level interface. It is known to work with
all modern Linux kernels and BSD systems (FreeBSD, NetBSD, OpenBSD,
Darwin).