function __bak_help
  echo -e \
"Usage:
  $argv[1] SOURCE..."
end

function __bak
  set program $argv[2]
  if [ (count $argv) -gt 2 ]
    for file in $argv[3..-1]
      function bak_name
        # trim / for directories
        set file (echo $argv[1] | sed 's/\/$//')
        echo "$file.(date +"%Y%m%d_%H%M%S").bak"
      end

      eval $program $file (bak_name $file)
    end
  else
    __bak_help $argv[1]
  end
end

function __unbak
  set program $argv[2]
  if [ (count $argv) -gt 2 ]
    for file in $argv[3..-1]
		set re_bak '(.*)\.[0-9]{8,8}_[0-9]{6,6}\.bak'
		set file $argv[1] 
		set normalized (echo "$file" | sed -r "s/$re_bak/\1/g")

		function is_bak
			echo "$file" | perl -ne "print if /$re_bak/" > /dev/null
		end

		if test ! -e $file
			echo "File \"$file\" not exists! Cannot unbak \"$file\"."
		else if not is_bak $file
			echo "File \"$file\" don't meet bak files convention! Cannot unbak \"$file\"."
		else if test -e $normalized
			echo "File \"$normalized\" exists! Cannot unbak \"$file\"."
		else
			eval $program $file $normalized
		end
    end
  else
    __bak_help $argv[1]
  end
end