org-babel/README.org

• nix-org-babel
  • Rationale
  • Usage
    • Extracting source blocks from an Org file/string
      • tangleOrgBabel function
      • tangleOrgBabelFile function
    • Options
      • Languages
      • Filtering subtrees

nix-org-babel

This is an implementation of org-babel-tangle in Nix. Given an Org string, it extracts the contents of source blocks of a particular language.

Rationale

talyz/fromElisp provides support for Org, and it is also part of emacs-overlay, which apparently is used by many people for their own configs. However, I wanted to experiment with more advanced features such as excluding archived entries, and I wasn't sure if I could mix that with their code base. I needed the feature in my own project, and I wanted to put it under my control, so I wrote it from scratch.

Usage

Import the flake.

Extracting source blocks from an Org file/string

tangleOrgBabel function

This function takes an Org string and returns its source blocks.

Example:

  let
    tangle = lib.tangleOrgBabel {
      languages = [ "emacs-lisp" ];
    };
  in
  # Return a string
  tangle (builtins.readFile ./config.org)

Arguments:

1. An attribute set of options.
2. An Org input string.

tangleOrgBabelFile function

Similar to tangleOrgBabel, but this function takes a file as an argument and writes the output to a file.

Example:

  # Write to a file
  let
    pkgs = import nixpkgs {
      inherit system;
      overlays = [
        org-babel.overlay
      ];
    };
  in
  pkgs.tangleOrgBabelFile "init.el" ./config.org {
    languages = [ "emacs-lisp" ];
  }

Note that this function is provided in the overlay of the flake.

Arguments:

1. A string for the derivation name.
2. An input file path.
3. An attribute set of options.

Options

Languages

Example:

  {
    languages = [ "emacs-lisp" "elisp" ];
  }

Default: [ "emacs-lisp" "elisp" ]

Filtering subtrees

You can transform the input by specifying processLines option. It must be a function that takes a list of strings and returns a list of strings.

This library also contains excludeHeadlines function which can be used to exclude subtrees according to a predicate on the headline text, so you can use it in the option.

Example:

  {
    # Exclude archived subtrees
    processLines = excludeHeadlines (matchOrgTag "ARCHIVE");
  }

You can use the following predicates from this library:

tag

Returns true if the headline matches a tag given as the argument. The argument must be a string.

headlineText

Returns true if the headline matches the text given as the argument. The argument must be a string.