How to modify interactive function `occur` to a non-interactive function

Question

occur is an interactive compiled Lisp function in ‘replace.el’. The definition is as follows:

(defun occur (regexp &optional nlines region)
  (interactive
   (nconc (occur-read-primary-args)
          (and (use-region-p) (list (region-bounds)))))
  (let* ((start (and (caar region) (max (caar region) (point-min))))
         (end (and (cdar region) (min (cdar region) (point-max))))
         (in-region-p (or start end)))
    (when in-region-p
      (or start (setq start (point-min)))
      (or end (setq end (point-max))))
    (let ((occur--region-start start)
          (occur--region-end end)
          (occur--matches-threshold
           (and in-region-p
                (line-number-at-pos (min start end))))
          (occur--orig-line
           (line-number-at-pos (point)))
          (occur--orig-line-str
           (buffer-substring-no-properties
            (line-beginning-position)
            (line-end-position))))
      (save-excursion ; If no matches `occur-1' doesn't restore the point.
        (and in-region-p (narrow-to-region start end))
        (occur-1 regexp nlines (list (current-buffer)))
        (and in-region-p (widen))))))

When the above function is invoked, the user is prompted to input a regexp for searching.

What I want is to make a new function myoccur by hard-coding a regexp in the above function and make it non-interactive, so that I can conveniently invoke it. If a wrapper over the original occur can make it non-interactive, that would also be great. How should I do?

I'm pretty sure this question is a duplicate, but I don't have time now to search for that. Hopefully someone else will find the duplicate. If found, this should be closed as a duplicate. — Drew, Jan 24 '21 at 18:17
This question comes close: https://emacs.stackexchange.com/questions/3555/what-is-the-difference-between-a-function-and-a-command. The answer is to just call the command as an ordinary function, providing whatever arguments it needs. — Drew, Jan 24 '21 at 18:31
Does this answer your question? How to call an interactive function and pass arguments to it from within Elisp? — Drew, Jan 24 '21 at 18:33
Also: https://emacs.stackexchange.com/questions/23951/how-to-find-non-interactive-function-equivalents-of-elisp-interactive-functions — Drew, Jan 24 '21 at 18:39
The following answers my question: https://stackoverflow.com/questions/18733310/in-emacs-is-there-a-way-to-call-interactive-function-non-interactively-from-ini — Youjun Hu, Jan 25 '21 at 00:53

Youjun Hu · Answer 1 · 2021-01-24T07:15:13.000

I finally found a solution:

(global-set-key (kbd "C-x j") (lambda () (interactive) (occur "regexp" nil)))

I also found that \ needs to be escaped by another \ in the regexp, which is different from the regexp inputted in interactive mode. For example, to match all functions and subroutines defined in a Fortran code, the regexp should be:

^ *\\(\\(subroutine\\)\\|\\(function\\)\\)

while in the interactive mode, the regexp is:

^ *\(\(subroutine\)\|\(function\)\)

Update: The reason is that, which I found at emacs website, the string syntax for a backslash is \\

How to modify interactive function `occur` to a non-interactive function

1 Answers1