6

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. . . .

4
  • 1
    How about using with-temp-file?: gnu.org/software/emacs/manual/html_node/elisp/… I don't understand all the cl-stuff, but it probably is not necessary to use any of that. The same page of the manual also discusses write-region, which may also be helpful. See also with-temp-buffer: gnu.org/software/emacs/manual/html_node/elisp/…
    – lawlist
    Nov 21, 2015 at 16:49
  • I guess I'll go Googling after elisp examples again. Your suggestions don't seem to do normal file read-write. There's only "buffer" manipulations with "start" and "end" of buffer. I just want to take the output of org-element-parse-buffer and write it to a file directly. Sure, I could do buffer work, but can't I just do normal file stuff in elisp?
    – 147pm
    Nov 21, 2015 at 17:04
  • Thank you for the Common Lisp snippet, I have been looking for something similar for some time. While in elisp, sometimes I prefer to use "cl-lib" available commands, to maintain context switching to a minimum between my two favourite languages.
    – gsl
    Nov 22, 2015 at 8:10
  • 2
    Using buffers is the normal way of operation in elisp, just like using callbacks it normal in JS. Better get used to it.
    – wasamasa
    Jan 12, 2016 at 6:34

2 Answers 2

10

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.

4
  • Riiigt. Buffers are cool, I know. So I did this: (defvar bufpar) then (setf bufpar (org-element-parse-buffer)) then (with-temp-file "test.ast" (insert (format "%s" bufpar))) and that worked. But just this ... (insert (org-element-parse-buffer))... did not. Not sure why. . . .
    – 147pm
    Nov 21, 2015 at 18:17
  • Did you check C-h f insert? That function expects strings or chars as its arguments. Try using format to get a string, like you did for your with-temp-file example.
    – Drew
    Nov 21, 2015 at 18:44
  • There are some caveats as discussed here
    – clemera
    Dec 7, 2018 at 14:47
  • @clemera - FYI that link is now 404'ed.
    – ocodo
    May 29 at 0:58
8

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")

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