Get contents of a named source block

Question

The other day I wanted to put the contents of a source code block into a header argument of another block. I couldn't find any ready to use function to do that though, so I came up with this:

(defun extract-src-content (name)    
  (save-excursion
    (org-babel-goto-named-src-block name)
    (car (nthcdr 21 (cadr (org-element-at-point))))))

But that doesn't seem to be right. First my elisp experience is not that vast so I don't know how to extract the value for the :value key out of (cadr (org-element-at-point)) so I just took the 21th element which can't be right and will probably break at the next org update. Second I still think there should be an org-function available to extract the contents of a named source code block, since it has to have a way to do that for export or editing.

Someone has an answer to either question?

• What's the right way to extract the value after :value out of (cadr (org-element-at-point))?
• Is there a ready to use org-function (or even org-syntax) to accomplish the same thing?

Bonus question

• I tried to ask this on the #org-mode irc channel, but even though there are a lot of joined users it seems to be dead. Why is it still linked on http://orgmode.org/community.html then?

Answer 1

Sometimes it helps to formulate a question to realize the answer. I did another look into the org-mode sources and found org-element-property so I can do

(org-element-property :value (org-element-at-point))

instead of (car (nthcdr 21 (cadr (org-element-at-point)))) which is much better and according to John Kitchin also the built in way to do it.

Answer 2

I would just use the builtin noweb functionality: set the option :noweb yes and refer to the quoted code by <<blockname>> in the other block:

#+NAME: sine
#+BEGIN_SRC python
  import math

  x=math.sin(math.pi)
#+END_SRC

#+BEGIN_SRC python :noweb yes :results output :exports results
  text="""
  <<sine>>
  """
  print text
#+END_SRC

#+RESULTS:
: 
: import math
: 
: x=math.sin(math.pi)
:

---

Edit: To supress the two linebreaks (before and after the code) that are introduced by having the """ in separate lines, you can use

#+BEGIN_SRC python :noweb yes :results output :exports results
 text="""\
 <<sine>>
 """[:-1]
 print text
#+END_SRC

But this is a python detail -- and python wizards surely know a more elegant way. Other languages might need other solutions, or will be fine directly (not every language complains when a string goes over a line break).

Just note, that anything before the << will be repeated for every source line, so you can easily comment out this for example.

Answer 3

I was led to my preferred answer to that question by a comment (Thank you! @Mutbuerger ) :

You may use (cadr (org-babel-lob--src-info NAME)) from ob-lob instead.

This brought me to:

(org-babel-expand-noweb-references (org-babel-lob--src-info NAME))

The other solution with (org-element-at-point) didn't feel "idiomatic" for cases, where you are not with point at the desired src-block, and thus have to (save-excursion (org-babel-goto-named-src-block ..., which is "Remember, where you are, virtually move the cursor to the wanted source, and only then read.

Sure, the approach from AA works, but I looked for a solution, that "doesn't move the cursor" (or at least does it transparently), and feels more "idiomatic". Since comments can disappear, I'm using this to make the org-babel-lob--src-info-solution from @Mutbuerger more (permanently) visible.

This will also expand noweb-refs, if enabled for the src-block.