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_help
  echo -e \
"Usage:
  $argv[1]bak SOURCE..."
end

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