Fast incremental file transfer using Merkle-Hash-Trees

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LTS Haskell 6.35:
Stackage Nightly 2016-05-25:
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MIT licensed and maintained by Emin Karayel
This version can be pinned in stack with:sync-mht-,5562


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Fast incremental file transfer using Merkle-Hash-Trees


A command line tool that can be used to incrementally synchronize a directory hierarchy with a second one. It is using a Merkle-Hash-Tree to compare the folders, such that the synchronization time and communication (round) complexity grows only logarithmically with the size of the directories (assuming the actual difference of the directories is small).

The communication happens through standard streams between parent and child processes, which can easily be routed through remote command execution tools.


The following command

sync-mht -s foo/ -d bar

will synchronize the local folder bar/ with the local folder foo/, but

sync-mht -s foo/ -d remote:/bar -r "ssh [email protected] sync-mht"

will synchronize the folder bar/ in the home directory of the user fred on the host machine with the local folder foo/.

It is also possible to use it with docker, e.g.

sync-mht -s foo/ -d remote:/bar -r "docker run -i --volumes-from bar ekarayel/sync-mht sync-mht"

to synchronize the folder /bar (of the container named bar) with the local folder foo/.

Note that: The options -a -u –delete respectively, allow copying of files to the target directory, updating files that are already in the target directory - not matching the contents in the source directory and deleting files that are in the destination directory but not in the source directory.


Installing sync-mht can be done using stack with the following steps:

git clone --recursive
cd sync-mht
stack exec runhaskell configure.hs
stack install