Secure Copy is a UNIX standard used to transfer files from one computer to another. He's how to use the function in macOS, all via the Terminal window.

You can run a series of Linux commands to copy multiple files to a folder or copy a single file to multiple folders, but you can save time and trouble by using xargs, loops and scripts.

Learn how to use the scp command to transfer files securely with this step-by-step tutorial by expert Jack Wallen.

It can be used to copy individual files as well, and has options for applying file system compression to files, or at least maintaining compression when copying a compressed file to another ...

The do "only show which files would be copied" without the "only copy existing files." Then you can diff the output of those commands and find out what didn't copy.