Join Lines By A Separator in Emacs

So sometimes I need to join a few lines by a separator while I'm coding, for example, turn the below lines,


into foo + bar + baz. (This is a silly example, I will update if I come up with a better one :-P )

When I was in a rush in the past, I usually baked a keyboard macro temporarily and then applied it to achieve this goal, thought reliable, it's a little bit cumbersome to record it. So I wonder maybe it would be a good idea to have a command for it.

(defun w/join-lines (specify-separator)
  "Join lines in the active region by a separator, by default a comma.
Specify the separator by typing C-u before executing this command.

Note: it depends on s.el."
  (interactive "P")
  (require 's)
  (unless (region-active-p)
    (message "select a region of lines first."))
  (let* ((separator (if (not specify-separator)
                      (read-string "Separator: ")))
         (text (buffer-substring-no-properties
         (lines (split-string text "\n"))
         (result (s-join separator lines)))
    (delete-region (region-beginning) (region-end))
    (insert result)))

So when the task comes up the next time, with this command, I will just select the lines as a region and then M-x w/join-lines to join the lines there. And, if I want a separator other than a comma, I can do that by typing C-u M-x w/join-lines, then it will prompt me to type a separator first, before doing the job.


See also

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