How to mark a code block in Org mode

Question

I am trying out the literate programming features of org mode and loving it! I will be using the noweb syntax of double angle brackets <<...>> heavily.

I want the named block to be inserted into the place of the double-brackets as intended, when I tangle the file (obviously)

However, when I export to HTML, I don't want the named block to be expanded, and just make <<block-name>> show up instead. This is useful to hide housekeeping code, since that often distracts my reading while reading the documentation.

In brief, how do I prevent expansion of <> while exporting to HTML and allow it while tangling?

Answer 1

The header argument :noweb no-export (or another option, dpending on your need) will help you. See here for more information.

EDIT: As suggested by @Drew a small summary of the :noweb arguments. The table below shows with which argument the code block will be expanded before what action:

| :noweb argument| evaluate | tangle | export  |
|----------------+----------+--------+---------|
| no             |          |        |         |
| yes            | yes      | yes    | yes     |
| tangle         |          | yes    |         |
| no-export      | yes      | yes    |         |
| strip-export   | yes      | yes    | removed |
| eval           | yes      |        |         |

Here a small example that shows how to apply the header argument to the source block:

* Example Use
#+begin_src sh :noweb-ref all
echo "all"
#+end_src

#+begin_src sh :noweb no-export :tangle example.sh
<<all>>
echo "more"
#+end_src

Please note that you have more options to set the header arguments. You can set them for example system wide or on a per file and subtree basis:

* Header arguments
** System wide
Set variable ~org-babel-default-header-args~:
#+BEGIN_SRC emacs-lisp
(setq org-babel-default-header-args '((:exports . "code")))
#+END_SRC
** Per file
#+property: header-args       :eval no
#+property: header-args:ditaa :eval yes

*** Per Subtree
    :PROPERTIES:
    :header-args:    :cache yes
    :END: