Minimalistic, multi-machine sync.
m3sync is a multi-directional (non-concurrent) file synchronization tool, with minimal requirements. In fact, the only requirement (other than POSIX) is the wonderfully robust and efficient rsync.
While m3sync does not allow for concurrency, it solves for many common use cases, and can be an effective synchronization utility, provided the user understands the limitations.
POSIX and mostly POSIX-compliant systems should be compatible with m3sync. The feature set is purposefully minimal to acheive maximum portability, and in order to limit external dependencies.
This tool began as a thought experiment on how to create a bi-directional file synchronization tool using only utilities that are commonly available at every (POSIX) command line.
Usage:
m3sync [-cdhnov] source_dir target_uri