I suppose I could compare the number of files in the source directory to the number of files in the target directory as cp progresses, or perhaps do it with folder size instead? I tried to find examples, but all bash progress bars seem to be written for copying single files. I want to copy a bunch of files (or a directory, if the former is not possible).
You can also use rsync
instead of cp
like this:
rsync -Pa source destination
Which will give you a progress bar and estimated time of completion. Very handy.