How could rsync be improved so that others won't have to struggle so much to find out about --modify-window=1?

Jason Spiro jasonspiro4 at
Tue Nov 25 00:59:09 GMT 2008

I am running rsync 3.0.4 on Cygwin. Before, when I resumed interrupted rsyncs,
every file would be re-copied all over again. I struggled to find an answer
until now I found it: I needed to specify --modify-window=1, since one of the
disks is FAT32. How could rsync be improved so that others won't have to
struggle so much?

Here are some options:

1.  At the start of each run, rsync should check the filesystem types, and if
one fs type name contains "user" or "system" (this means rsync is running on on
Cygwin 1.5; only the unreleased Cygwin 1.7 can report the actual fs types) or
"dos" or "fat", then it should enable modify-window=1.

2.  Alternatively, if rsync finds that there are a lot of almost-hits that
differ only by a few seconds' timestamp, rsync should enable modify-window=1

3.  Or, rsync should create a few temporary files on the source and target disks
to check the disks' timestamp resolutions, then delete the temp files.  Or

4.  Or, rsync could look at the timestamps of the files that are already on the
source and target disks and infer the timestamp resolutions from that.

5.  Or, rsync could use modify-window=1 by default unless the user declines it.
 ( implies
that the default was probably changed to 1 on Cygwin only in 2003, but I assume
the default is now 0 because of the original problem I had.)

What do you think?

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