What is the canonical way of installing Elixir or Erlang > 19 with `nix` on a non-NixOS system?

Question

Please explain it as you would to a 10-year-old, from the point after the Nix package manager is installed on a non-NixOS machine. For example, I am on a Mac, and there isn\

Answer 1

You can create a dedicated shell for use with your project, and avoid installing the runtime globally/for current user.

Example of minimal nix shell for Elixir on Erlang/OTP 20:

The contents of default.nix file:

with import  {};

stdenv.mkDerivation rec {
    name = "env";
    env = buildEnv { name = name; paths = buildInputs; };
    buildInputs = [
        beam.packages.erlangR20.elixir
        inotify-tools
    ];
}

Then in terminal, navigate to the directory where default.nix is saved, and invoke nix-shell. You should drop into a shell which has iex and mix available.