How do I duplicate a whole line in Emacs?

Question

I saw this same question for VIM and it has been something that I myself wanted to know how to do for Emacs. In ReSharper I use CTRL-D for this action. What is the least num

Answer 1

With prefix arguments, and what is (I hope) intuitive behaviour:

(defun duplicate-line (&optional arg)
  "Duplicate it. With prefix ARG, duplicate ARG times."
  (interactive "p")
  (next-line 
   (save-excursion 
     (let ((beg (line-beginning-position))
           (end (line-end-position)))
       (copy-region-as-kill beg end)
       (dotimes (num arg arg)
         (end-of-line) (newline)
         (yank))))))

The cursor will remain on the last line. Alternatively, you might want to specify a prefix to duplicate the next few lines at once:

(defun duplicate-line (&optional arg)
  "Duplicate it. With prefix ARG, duplicate ARG times."
  (interactive "p")
  (save-excursion 
    (let ((beg (line-beginning-position))
          (end 
           (progn (forward-line (1- arg)) (line-end-position))))
      (copy-region-as-kill beg end)
      (end-of-line) (newline)
      (yank)))
  (next-line arg))

I find myself using both often, using a wrapper function to switch the behavior of the prefix argument.

And a keybinding: (global-set-key (kbd "C-S-d") 'duplicate-line)