I thought about temp files, but that makes the file names cryptic which is
inconvenient for communication without people outside org.. also, I tend
recompile figures many times which would cause a lot of cluttering files
that are hard to delete since you don't know which file is the one
currently linked in your org file...

Anyway, I made this instead which appears to work as I intended


(defun org-babel-about-to-overwrite-file ()
  (let ((info (org-babel-get-src-block-info)))
    (setq result-file (cdr (assoc :file (nth 2 info))))
    (if (save-excursion
  (goto-char 0)
  (re-search-forward (concat ":file +" result-file) nil t)
  (re-search-forward (concat ":file +" result-file) nil t))
(message (concat result-file " defined in more than one source block"))
      (org-babel-execute-maybe))))

(add-hook 'org-ctrl-c-ctrl-c-hook 'org-babel-about-to-overwrite-file)





2013/10/12 Charles Berry <ccberry@ucsd.edu>

> John Kitchin <jkitchin <at> andrew.cmu.edu> writes:
>
> >
> >
> >
> > I have a related kind of problem. When preparing notes
> > for a class, I may end up with 70 code blocks in an org file, many of
> > which create graphics. I am always worried about accidentally using the
> > same filename and overwriting a graphic from an earlier block. A unique,
> >  but reproducible filename would be sufficient for my needs.
> >
>
> Header arg values can be elisp calls. You can use `make-temp-file'.
>
> So every time this block is executed, a new file is created and the
> file link is added to the results.
>
> #+BEGIN_SRC R :results output append :file (make-temp-file "temp")
> cat(date(),"\n")
> #+END_SRC
>
> #+RESULTS:
> [[file:/var/folders/kb/2hchpbyj7lb6z76l0q73w_fh0000gn/T/temp302IjV]]
> [[file:/var/folders/kb/2hchpbyj7lb6z76l0q73w_fh0000gn/T/temp3028Lu]]
>
> See `temporary-file-directory', too, if you want to use this, as the
> default may not be what you intend.
>
>
> You might want to use this:
>
> #+BEGIN_SRC emacs-lisp
>   (defun local-tfile (file)
>     (let ((temporary-file-directory "."))
>       (make-temp-file file)))
> #+END_SRC
>
> Then the files go in the local directory when this is executed:
>
> #+BEGIN_SRC R :file (local-tfile "tfile") :results output append
> cat(date(),"\n")
> #+END_SRC
>
> You might not want `append' in this case.
>
>
> HTH,
>
> Chuck
>
> [rest deleted]
>
>
>
>
>