eval elisp code to fill org-babel header arguments

Question

I use many org files with figures generated by source code blocks.

By example, in an org mode file long/path/document.org I have:

#+BEGIN_SRC dot :file my_fig.png  :exports results
digraph {
  A->B
  B->C
  C->A
}
#+END_SRC

However, to keep a clean directory/files hierarchy I want store the generated figures (or data) in a subdirectory associated to each org mode document, for instance: long/path/document-extra/my_fig.png.

#+BEGIN_SRC dot :file long/path/document-extra/my_fig.png  :exports results
digraph {
  A->B
  B->C
  C->A
}
#+END_SRC

Doing that manually is tedious, how to automate this?

Answer 1

I define functions at the end of my org mode file (thanks Local variables)

#+BEGIN_SRC dot :file (fig_name "my_fig") :exports results
digraph {
  A->B
  B->C
  C->A
}
#+END_SRC

...

# end of my org mode file

# Local Variables:
# eval: (defun fig_name(name) (concat (file-name-sans-extension (buffer-file-name)) "-extra/" name ".png"))
# End:

The function (fig_name "my_fig") automatically creates the right filename, something like:

: /home/XXX/GitLab/YYY/Bibliography/jiang11_rankin_hodge_theor-notes-extra/my_fig.png

As defined we assumed that the directory long/path/document-extra/ exists, but this can be also checked and eventually created in the fig_name function.