#!/usr/bin/env zsh
##? append date/time and `.bak` to file

local now f
now=$(date +"%Y%m%d-%H%M%S")
for f in "$@"; do
  if [[ ! -e "$f" ]]; then
    echo "file not found: $f" >&2
    continue
  fi
  cp -R "$f" "$f".$now.bak
done