Literate Programming with Org Mode

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You can navigation and filter Literate Programming document logic with headlines and tags. When a file grows large, organize your document with clear structure and better tags group is very necessary.

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Org Mode Babel are technology that can evaluate source code blocks and insert result into Org buffer. Babel is powerful by backend with many different programming languages and tools. On essention, Babel is send source code block text to another binary to be evaluated, then return the result to be inserted in Org buffer.

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Tangling functionality is controlled by the tangle family of tangle header arguments. These arguments can be used to turn tangling on or off (the default), either for the code block or the Org-mode heading level.

The following code blocks demonstrate how to tangle them into a single source code file using org-babel-tangle.

The following two code blocks have no tangle header arguments and so will not, by themselves, create source code files. They are included in the source code file by the third code block, which does have a tangle header argument.

In the Org-mode file:

#+name: hello-world-prefix
#+begin_src shell :exports none
  echo "/-----------------------------------------------------------\\"
#+end_src

HTML export of code: In the Org-mode file

#+name: hello-world-postfix
#+begin_src shell :exports none
  echo "\-----------------------------------------------------------/"
#+end_src

HTML export of code: The third code block does have a tangle header argument indicating the name of the file to which the tangled source code will be written. It also has Noweb style references to the two previous code blocks. These references will be expanded during tangling to include them in the output file as well.

In the Org-mode file:

#+name: hello-world
#+begin_src shell :tangle hello.sh :exports none :noweb yes
  <<hello-world-prefix>>
  echo "|                       hello world                         |"
  <<hello-world-postfix>>
#+end_src

HTML export of code: Calling org-babel-tangle will result in the following shell source code being written to the hello.sh file:

echo "/-----------------------------------------------------------\\"
echo "|                       hello world                         |"
echo "\-----------------------------------------------------------/"

#!/usr/bin/env sh

# [[file:~/org/temp/index.org::*Noweb test][hello-world]]

echo "/-----------------------------------------------------------\\"
echo "|                       hello world                         |"
echo "\-----------------------------------------------------------/"
# hello-world ends here

In addition, the following syntax can be used to insert the results of evaluating a code block, in this case one named example-block.

# <<example-block()>>

Any optional arguments can be passed to example-block() by placing the arguments inside the parentheses following the convention defined when calling source block functions (see the Library of babel). For example,

# <<example-block(a=9)>>

sets the value of argument a equal to 9. Note that these arguments are not evaluated in the current source-code block but are passed literally to example-block().

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• org-babel-goto-named-src-block
• org-babel-goto-named-result
• org-babel-goto-src-block-head

You can jump back in mark ring with [M-,] / org-mark-ring-goto.