Install Nix

Link to nixos page.

The rest

Start with this...

$ mkdir ~/lets-learn-nix
$ cd ~/lets-learn-nix

...done. Copy the following and paste it into a file name shell.nix.

# file: shell.nix
let
  pkgs = import (builtins.fetchGit {
    url = "https://github.com/NixOS/nixpkgs-channels";
    ref = "refs/heads/nixos-19.09";
  }) {}
in pkgs.mkShell {
  buildInputs = with pkgs; [
    git
  ];
  NIX_PATH = "nixpkgs=${pkgs}";
};

...then...

$ nix-shell