function __bak_name
  # trim / for directories
  set arg (echo $argv[1] | sed "s/\///")
  echo "$arg.(date +"%Y%m%d_%H%M%S").bak"
end

function __bak
  set program $argv[1]
  for arg in $argv[2..-1]
    eval $program $arg (__bak_name $arg)
  end
end