Sorting lines with accented characters

Question

When sorting the lines by sort-lines the lines beginning with ä comes after the lines starting with z. It would be nice if the lines could be sorted ignoring the accents, Umlauts, etc, like in a dictionary. Ideally a line starting with ändern should be come after a line starting with anderen.

There is simple solution for searching accented characters mentioned in https://superuser.com/a/675172/ but can not be used here. I am wondering if that solution can be adapted in this situation.

Answer 1

I use this function for that

(defun my-sort-lines ()
    (interactive)
    (shell-command-on-region (point-min) (point-max) "LC_COLLATE=en_US.UTF-8 sort" (buffer-name) t ))

EDIT: To sort region or buffer:

  (defun my-sort-lines-buffer ()
    (interactive)
    (shell-command-on-region (point-min) (point-max) "LC_COLLATE=en_US.UTF-8 sort" (buffer-name) t ))
  (defun my-sort-lines-region (start end) 
    (interactive "r") 
    (shell-command-on-region start end "LC_COLLATE=en_US.UTF-8 sort" (buffer-name) t))
  (defun my-sort-lines-region-or-buffer ()
    (interactive)
    (save-excursion
      (if (region-active-p)
          (progn
            (my-sort-lines-region (region-beginning) (region-end))
            (message "Sorted selected region"))
        (progn
          (my-sort-lines-buffer)
          (message "Sorted buffer")))))