It would be nice if rsync would print the subdirectory path it is currently traversing on the sending host to stderr on receipt of some signal, perhaps with a percent done as well. The dd command does something similar; when sent SIGUSR1, it prints its i/o statistics and how much has been copied.
The reason this would be nicer than rsync's --verbose and --progress options is because they're *too* verbose -- they print messages for almost everything. One has to redirect the output from them to a file, otherwise anything one is looking for will probably scroll off the terminal before it can be read.
A signal would let the user get a quick overview of what is happening right now, when the information is wanted, emitting no more than a line or two of information. Printing of the currently traversed path would help in diagnosis of performance problems that may be caused by the data itself (thousands or millions of files in a folder).
Most of this could be done with current options by enabling --verbose and redirecting output to a file, and then running tail on that file, but it's inconvenient, and probably the file would just be deleted later after being read.
I really like this idea. I'm using rsync extensively during a storage migration, as it's the only tool that can quickly and effectively synchronize a source tree to a destination tree when there are periodic changes to the source tree. I've had so many rsyncs (in screen) going over the last few months that I can practically do it in my sleep ... and when you're synchronizing millions of files in a provider subdirectory, it takes quite a while, and it would be really nice to be able to hit a key or send a signal and have it tell you what source file it just did a stat on.
This is perhaps not exactly the correct place for this next comment, but it's the only place I have at the moment: Thank you to everyone who made rsync possible.
You can send 3.2.0 (and later) either a SIGINFO or SIGVTALRM signal to ask it to output some progress info.