Extracting md4 hash info from rsycn

Matt McCutchen hashproduct+rsync at gmail.com
Fri Aug 31 20:25:53 GMT 2007

On 8/31/07, Cliff <cliffdickerson at gmail.com> wrote:
> I was wondering if its possible to extract the checksum that rsycn creates
> to verify the transfer of a file was successful? Id like to store it so I
> can verify the files at a later time.
> I was thinking I could just run an md5sum prior to rsync, but then I figured
> if rsycn is already doing it maybe I can just copy that checksum. I have
> sever tb's of smaller files I need to transfer
> so not having to generate a second checksum for each file would save me
> loads of cycles.

The attached patch to the current CVS rsync adds a log escape %C that
expands to the sender's post-transfer checksum of a file.  If you use
an rsync from the CVS source plus this patch on both sides, you can
use a command like the following to log the MD5 checksums of
transferred files:

rsync <options> -v --out-format='%C %n' --checksum-seed=-1 src/ dest/

(If you want checksums of non-transferred files, run your own md5sum
command for those files.)

Perhaps Wayne will be so kind as to add the patch to patches/ of the
source tree in CVS.

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