Learn Nix with `from-zero-to-nix`

[thanhnguyen2187]

The first lesson is nix run:

echo "Hello Nix" | nix run "nixpkgs#ponysay"

• nixpkgs is the packages
• ponysay is the CLI command

---

What happened here? The Nix CLI did a few things:

• It used the nixpkgs flake reference to pull in some Nix code and targeted the ponysay flake output (more on this later).
• It built the ponysay package and stored the result in the Nix store.
• It ran the executable at bin/ponysay from the ponysay package.

In Nix, every program is part of a package. Packages are built using the Nix language. The ponysay package has a single program (also called ponysay) but packages can contain multiple programs as well as man pages, configuration files, and more. The ffmpeg package, for example, provides both ffmpeg and ffprobe.

[thanhnguyen2187]

More on terminology:

• package: or a derivation, is a specification on how to build a program. It is in the form of a .nix file, which uses Nix programming language.

• flake:

  A Nix flake is a directory with a flake.nix and flake.lock at the root that outputs Nix expressions that others can use to do things like build packages, run programs, use development environments, or stand up NixOS systems. If necessary, flakes can use the outputs of other flakes as inputs.

[thanhnguyen2187]

The second lesson is nix develop:

nix develop "github:DeterminateSystems/zero-to-nix#example"

It raised:

error: unsupported tarball input attribute 'rev'
(use '--show-trace' to show detailed location information)

[thanhnguyen2187]

The third lesson is nix build:

A command like this:

nix build "nixpkgs#bat"

Would build bat (a cat alternative in Rust) from scratch, and create a folder named result that contains the built result:

./result/bin/bat --version
# bat 0.24.0

We can also define a local flake.nix file like this:

{
  description = "C++ example flake for Zero to Nix";

  inputs = {
    nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.2305.491812.tar.gz";
  };

  outputs = { self, nixpkgs }:
    let
      # Systems supported
      allSystems = [
        "x86_64-linux" # 64-bit Intel/AMD Linux
        "aarch64-linux" # 64-bit ARM Linux
        "x86_64-darwin" # 64-bit Intel macOS
        "aarch64-darwin" # 64-bit ARM macOS
      ];

      # Helper to provide system-specific attributes
      forAllSystems = f: nixpkgs.lib.genAttrs allSystems (system: f {
        pkgs = import nixpkgs { inherit system; };
      });
    in
    {
      packages = forAllSystems ({ pkgs }: {
        default =
          let
            binName = "zero-to-nix-cpp";
            cppDependencies = with pkgs; [ boost gcc poco ];
          in
          pkgs.stdenv.mkDerivation {
            name = "zero-to-nix-cpp";
            src = self;
            buildInputs = cppDependencies;
            buildPhase = "c++ -std=c++17 -o ${binName} ${./main.cpp} -lPocoFoundation -lboost_system";
            installPhase = ''
              mkdir -p $out/bin
              cp ${binName} $out/bin/
            '';
          };
      });
    };
}

And build the local file ourselves:

nix build

The default package is defined and built in this case.