What I particularly like about Nix is its ability to encapsulate environments. No need to remember how to set up a certain environment, just encode it in a Nix expression, check it into version control and use nix-shell. This is especially useful when having to occasionally deal with certain environments, without being too familiar with the technical details. For me one such example is Jekyll, a Ruby application (and I am not familiar with Ruby).

I have created a new Jekyll blog and used bundix to convert a Gemfile into a Nix expression (gemset.nix). To this, add the following default.nix:

with (import <nixpkgs> {});
  ghPagesEnv = bundlerEnv {
    name = "mtesseract-github-pages-env";
    inherit ruby;
    gemdir = ./.;
  shell = stdenv.mkDerivation {
    name = "mtesseract-github-pages";
    buildInputs = [ ghPagesEnv ];
  serve = stdenv.mkDerivation {
    name = "mtesseract-github-pages-serve";
    buildInputs = [ ghPagesEnv ];
    shellHook = ''
      exec ${ghPagesEnv}/bin/jekyll serve --watch

This expression contains two attributes: shell and serve. Thus, nix-shell -A shell spawns an interactive shell having Jekyll in path, while nix-shell -A serve spawn Jekyll to serve the page at http://localhost:4000. For details, check out the repository of this blog.