How to do a simple write to file

Question

I simply need to take the output of org-element-parse-buffer and put it in a file -- maybe with some "if-does-not-exist" etc. bells and whistles. In CL I have with-open-file and write as tools. For example, here's CL to read a file containing lines like foo=bar and output to a new file like this (foo . bar)

(defun arabic_to_roman (filename)
  (cl-flet ((read-it ()
                  (with-open-file (in filename
                                      :direction :input
                                      :if-does-not-exist nil)
                                  (loop for line = (read-line in nil)
                                        for pos = (position \= line)
                                        while line collect (cons (subseq line 0 pos)
                                                                 (subseq line (1+ pos))))))
         (write-it (list)
                   (with-open-file (cl-stream #p"ar_out.txt"
                                           :direction :output
                                           :if-exists :overwrite
                                           :if-does-not-exist :create)
                                   (write list :stream stream :escape nil :readably nil :pretty nil))))
    (write-it (read-it))
    'done-read-write))

This is someone abstruse compared to other languages -- but then I don't find anything like this in elisp. How is read-write done in elisp. What I find seems only buffer-oriented. . . .

Answer 1

Use with-temp-file; this is documented at M-: (info "(elisp) Writing to Files") (also available online).

This takes a filename or path and a list of body forms. It creates a temporary buffer, then executes the body forms with that new buffer as the current buffer, then writes the contents of that buffer to the file, then deletes the temporary buffer.

Don't be so down on buffers; you can think of them as strings with cursors, if you'd like. If you have a string and want to put it into a buffer, just insert it: (insert (org-element-parse-buffer ...)).

Followup:

I should have double-checked, but since org-element-parse-buffer doesn't return a string, you'll need to convert it to one first. As Drew mentioned, (format "%s" (org-element-parse-buffer)) will work.

Answer 2

f third-party library has f-write-text and some other file manipulation functions, such as f-exists? predicate:

(f-write-text "some string" 'utf-8 "path/to/my/file.txt")