Re: org babel before excute hook

[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

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