Unison is a file-synchronization tool for Unix and Windows. It allows two replicas of a collection of files and directories to be stored on different hosts (or different disks on the same host), modified separately, and then brought up to date by propagating the changes in each replica to the other.

Unison shares a number of features with tools such as configuration management packages (CVS, PRCS, Subversion, BitKeeper, etc.), distributed filesystems (Coda, etc.), uni-directional mirroring utilities (rsync, etc.), and other synchronizers (Intellisync, Reconcile, etc). However, there are several points where it differs:

• Unison runs on both Windows and many flavors of Unix (Solaris, Linux, OS X, etc.) systems. Moreover, Unison works across platforms, allowing you to synchronize a Windows laptop with a Unix server, for example.
• Unlike simple mirroring or backup utilities, Unison can deal with updates to both replicas of a distributed directory structure. Updates that do not conflict are propagated automatically. Conflicting updates are detected and displayed.
• Unlike a distributed filesystem, Unison is a user-level program: there is no need to modify the kernel or to have superuser privileges on either host.
• Unison works between any pair of machines connected to the internet, communicating over either a direct socket link or tunneling over an encrypted ssh connection. It is careful with network bandwidth, and runs well over slow links such as PPP connections. Transfers of small updates to large files are optimized using a compression protocol similar to rsync.
• Unison is resilient to failure. It is careful to leave the replicas and its own private structures in a sensible state at all times, even in case of abnormal termination or communication failures.
• Unison has a clear and precise specification.
• Unison is free; full source code is available under the GNU Public License.

Windows

Thanks to Karl M, here are native MSVC Windows version (GTK+ and text versions in each zip file): 2.26.14, 2.27.57 (2008.01.20, stable), 2.28.34 (2008.01.20, unstable)
A GTK+ 2 runtime environment, needed to run this version, may be downloaded from the Pidgin project.

I copy the unison.exe to the target and host systems (in the path), then invoke
Unison path UNC_path
and it works... Uses NetBIOS copy in this mode.

Introduction

Harmony is framework for defining, updating, and synchronizing views over strings, trees, and relations. It can be used, for example, to synchronize the bookmark files of several different web browsers, to convert address books represented in vCard to CSV, and to map between BiBTeX and RIS-formatted bibliographic databases.

A central theme of the project is bringing ideas from programming languages to bear on a set of problems more commonly regarded as belonging to the purview of databases. Views are usually discussed in the context of databases, but actually arise in a host of applications across many diverse areas of computing. In many of these applications, is necessary to apply an update to the view, and have the update be reflected back on the source. Unfortunately, the view update problem remains largely unsolved; except in very simple cases, views are read-only. Our goal is to develop programming languages in which programmers can specify both how to calculate a view, and how to translate updates to a view back to the source, and to use these bidirectional programs—called lenses—to build converters and synchronizers for a variety of real-world data formats.