When editing human language text and moving text fragments around, I frequently run into the problem that whitespace moved at the beginning or end of a fragment doesn't fit into the new position. For example, consider this paragraph:

This is the first sentence.  This is the second sentence.  These
three sentences are the whole paragraph.

If I move the last sentence before the first one by kill+yank, I have either leading or trailing whitespace. A similar problem occurs in enumerations.

Another use case is if I want to insert a single word or expression which is in the kill ring without any trailing or leading whitespace. For example, consider the word "very" in the kill ring, and the following sentence:

Such a minor mode would be useful.

After yanking, this may erroneously become:

Such a minor mode would bevery useful.

Is there a way to have white space in human texts adjusted automatically?

2 Answers 2


This seems to do what you have asked. By contrast if there is already extra white spaces, it keeps them as before.

  (defun yank-and-adjust-whitespace ()
  (if (equal (char-after) ?\s)
        (insert " ")
    (if (eolp) (if (bolp) (yank)
        (if (equal (char-before) ?\s)
          (insert " ")
      (insert " "))))

Like the answer of Eric Bailey you can associate the below shortcut.

(global-set-key "\C-y" 'yank-and-adjust-whitespace)

Using eolp/bolp was borrowed from https://emacs.stackexchange.com/a/13741/.

  • @wasamasa thanks for editing, I saw that you have changed ? to?\s. It seems that both work. I am interested to know about their differences.
    – Name
    Commented Jul 6, 2015 at 12:30
  • 1
    Correct, both are equivalent. The manual recommends ?\s though because it looks a lot less confusing than ? and ensures that you meant to match a space instead of mistyping.
    – wasamasa
    Commented Jul 6, 2015 at 12:42

Here's a function, delete-leading-whitespace-on-line to do as the name suggests:

(defun delete-leading-whitespace-on-line ()
  "Delete whitespace at the beginning of the current line."
  (let ((start (line-beginning-position))
        (end (line-end-position)))
      (delete-whitespace-rectangle start end nil))))

For trailing whitespace, I use M-x delete-trailing-whitespace.

To trigger these after yanks, you could do something like:

(defun yank-and-trim-whitespace ()
  "Yank and then trim whitespace on the line."

and bind it like:

(global-set-key "\C-y" 'yank-and-trim-whitespace)

You might also like to try Steve Purcell's whitespace-cleanup-mode, a minor mode that:

will intelligently call whitespace-cleanup before buffers are saved.

PS His GitHub account is a treasure trove of Emacs goodies.

  • I don't have the reputation yet, but here's a link to the pertinent documentation: gnu.org/software/emacs/manual/html_node/emacs/…
    – yurrriq
    Commented Jul 3, 2015 at 15:38
  • Are the call-interactively's necessary here? Can you not just call the functions?
    – erikstokes
    Commented Jul 3, 2015 at 16:27
  • @erikstokes, good catch. The call-interactively are redundant.
    – yurrriq
    Commented Jul 3, 2015 at 17:31
  • I think using call-interactively here would make it work with yank-pop.
    – politza
    Commented Jul 4, 2015 at 7:53

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