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

The defaults are horrible for this. However, you can extend Emacs to work like SlickEdit and TextMate, that is, copy/cut the current line when no text is selected:

(transient-mark-mode t)
(defadvice kill-ring-save (before slick-copy activate compile)
  "When called interactively with no active region, copy a single line instead."
  (interactive
   (if mark-active (list (region-beginning) (region-end))
     (message "Copied line")
     (list (line-beginning-position)
           (line-beginning-position 2)))))
(defadvice kill-region (before slick-cut activate compile)
  "When called interactively with no active region, kill a single line instead."
  (interactive
   (if mark-active (list (region-beginning) (region-end))
     (list (line-beginning-position)
           (line-beginning-position 2)))))

Place the above in .emacs. Then, to copy a line, M-w. To delete a line, C-w. To duplicate a line, C-a M-w C-y C-y C-y ....

Answer 2

install duplicate-thing from melpa:

M-x package-install RET duplicate-thing

and add this keybinding to init file :

(global-set-key (kbd "M-c") 'duplicate-thing)

Answer 3

As mentioned in other answers, binding key strokes to lisp code is a better idea than binding them to another key strokes. With @mw's answer, code duplicates the line and moves the mark to end of new line. This modification keeps the mark position at same column on the new line:

fun duplicate-line ()
  (interactive)
  (let ((col (current-column)))
    (move-beginning-of-line 1)
    (kill-line)
    (yank)
    (newline)
    (yank)
    (move-to-column col)))

Answer 4

My version of a function to duplicate a line that works nice with undo and doesn't mess with the cursor position. It was the result of a discussion in gnu.emacs.sources from November 1997.

(defun duplicate-line (arg)
  "Duplicate current line, leaving point in lower line."
  (interactive "*p")

  ;; save the point for undo
  (setq buffer-undo-list (cons (point) buffer-undo-list))

  ;; local variables for start and end of line
  (let ((bol (save-excursion (beginning-of-line) (point)))
        eol)
    (save-excursion

      ;; don't use forward-line for this, because you would have
      ;; to check whether you are at the end of the buffer
      (end-of-line)
      (setq eol (point))

      ;; store the line and disable the recording of undo information
      (let ((line (buffer-substring bol eol))
            (buffer-undo-list t)
            (count arg))
        ;; insert the line arg times
        (while (> count 0)
          (newline)         ;; because there is no newline in 'line'
          (insert line)
          (setq count (1- count)))
        )

      ;; create the undo information
      (setq buffer-undo-list (cons (cons eol (point)) buffer-undo-list)))
    ) ; end-of-let

  ;; put the point in the lowest line and return
  (next-line arg))

Then you can define CTRL-D to call this function:

(global-set-key (kbd "C-d") 'duplicate-line)

Answer 5

because i don't know, i'll start this round of golf with a slowball:

ctrl-k, y, y

Answer 6

With recent emacs, you can use M-w anywhere in the line to copy it. So it becomes:

M-w C-a RET C-y