backup a file or restore it if it ends in a bkp extension

bkp.sh

#!/usr/bin/env bash

# for each file, either back it up or restore it, in case it ends in a bkp extension

for f in "$@"; do
	p="${f%/}"
  [ "$p" != "${p%.bkp}" ] &&
	cp --archive --interactive --update --verbose "$p" "${p%.bkp}" ||
    cp -aiuv "${p}" "$p.bkp"
done; }