How can I compare two directories, one being a remote directory?

Question

I want to compare two directories, one is local and the other is on another machine.

How can I do that? Can I do it with diff?

Answer 1

I can think of two ways here..

1. Mount your remote directory locally, and then use diff as you would do on a local machine.

2. Use rsync:

rsync -avz --dry-run remote-user@remote-machine:remote-dir local-dir

This will show you the files that differ, but will not show you the actual diff. I think Unison supports diff also, but I have never used it and it does not seem to be under development any more.

Answer 2

Note that using diff will require the entire contents of the remote directory to be transferred over the network, which could become prohibitively slow if there are large files or large numbers of files involved.

My recommendation would be to first determine which files differ between the two machines (by using rsync -n --delete (-n causes it to only tell you what it would do, but without actually doing it; --delete will tell you if any files exist in the destination, but not in the source, because it will want to delete them) or by comparing md5sums. If you're looking for how they're different (rather than just if they're different), I would then use diff only on those specific files to see what the differences are.

Answer 3

Yes, you can do it with diff! User space applications such as "diff" don't know (and don't need to know) if a directory is local or remote.