Sort lines in a string

Question

Given I have a string that maybe came from a buffer, or a clipboard, or wherever; how do I sort-lines in it? Given that sort-lines only works with a region, I assume I have to put it to a temporary buffer, but I'm not aware of a common way of dealing with such tasks.

Googling the topic doesn't give anything relevant.

Answer 1

I'm not aware of a common way of dealing with such tasks.

with-temp-buffer and buffer-string are nice general helpers here.

(setq SORTED (with-temp-buffer
               (insert UNSORTED)
               (sort-lines nil (point-min) (point-max))
               (buffer-string)))

Answer 2

Here is one possible way to implement this using a temporary buffer:

(defun sort-string (string &optional reverse)
  "sorts an input string, using a temporary buffer"
  ;;(interactive "sto be sorted multiline string: ")
  (with-temp-buffer
    (insert string)
    (let ((beg (point-min))
      (end (point-max)))
      (sort-lines reverse beg end)
      (buffer-string)) ))

First a temprary buffer is created, then the given string is inserted, then the whole buffer is sorted, then the whole buffer is returned as a new string.

The additional parameter reverse can change the sort order.
To make this function a command, which you can call via M-x, uncomment the (interactive) line, but then you have to grab the output of the function in a useful way.

---

Evaluating following code pieces in the given order, results in the following output:

(setq my-string "zzzz\ndddd\nhhhhh\naaaaa")

"zzzz
dddd
hhhhh
aaaaa"

(setq my-string (sort-string my-string))

"aaaaa
dddd
hhhhh
zzzz"

my-string

"aaaaa
dddd
hhhhh
zzzz"

(setq my-string (sort-string my-string 'reverse))

"zzzz
hhhhh
dddd
aaaaa"

my-string

"zzzz
hhhhh
dddd
aaaaa"