Sync is a simple command-line utility for performing one-way directory or file synchronization.
It synchronizes the specified target to match the specified source. Only the target is modified.
Runs on any OS with the Java Runtime Environment (JRE 6+).
Sync is free and open source software written in Java and released under the GNU GPL license (version 3).

MAIN FEATURES:
* FLEXIBLE FILE-MATCHING: Match files by combinations of name, size, last-modified time, and CRC-32 checksum; by default, (name,size,time,CRC) are used.
* FLEXIBLE FILE TIME COMPARISON: Specify a time-tolerance (in milliseconds) when matching files by their last-modified time.
* FILENAME FILTER: Use a GLOB or REGEX filter for file/directory names, or their full (relative) pathnames.
* SIMULATION MODE: Sync can be run to simulate file operations, so that the target directory is not modified.
* UNATTENDED USAGE: With an appropriate choice of switches, Sync can be executed without user intervention.

See http://syncdir.sourceforge.net/ for the latest version, screenshots, documentation, and other information.