Can we copy files with incremental checksum computation?

Question

I know using rsync -c we can copy files and having them verified with checksum. The issue is that rsync first build a list of files and at the same time it computes the checksum for all files. This would take forever if you have millions of files. Is there a solution where the checksum is simply computed as the application reads the file streams for the copy task?

Answer 1

This should be the default behaviour for rsync since 3.0.0, assuming that you don't have all the files in one directory.

However, there are some options that force rsync to scan all the files up front; look at the man page and search for "incremental" for more details.