Nix flake

README.md

@@ -81,6 +81,24 @@ Or just the package, without the repository and so without updates: the
 `.deb` files are on the [release page](https://github.com/clainstone/cbirds/releases/latest),
 for `sudo apt install ./cbirds_*.deb`.
 
+### Nix flake
+
+Linux on x86_64 and aarch64, macOS on Apple silicon. With Nix and the
+`nix-command` and `flakes` experimental features enabled, run directly from
+this repository:
+
+```sh
+nix run github:clainstone/cbirds
+```
+
+Pass cbirds options after `--`, for example for sprites in Kitty or Ghostty:
+
+```sh
+nix run github:clainstone/cbirds -- --render kitty --hawks 2 --color ice
+```
+
+From a local checkout of this repository, use `nix run .`.
+
 ### From source
 
 ```

flake.nix

@@ -0,0 +1,59 @@
+{
+  description = "A flock of birds in your terminal";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "aarch64-darwin"
+      ];
+      forAllSystems = nixpkgs.lib.genAttrs systems;
+      # The version cbirds --version prints, so it moves with each release
+      version = nixpkgs.lib.pipe ./boids.c [
+        builtins.readFile
+        (nixpkgs.lib.splitString "\n")
+        (map (builtins.match "#define CBIRDS_VERSION \"(.*)\""))
+        (nixpkgs.lib.findFirst (m: m != null) null)
+        builtins.head
+      ];
+    in
+    {
+      packages = forAllSystems (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+        in
+        {
+          default = self.packages.${system}.cbirds;
+
+          cbirds = pkgs.stdenv.mkDerivation {
+            pname = "cbirds";
+            inherit version;
+            src = pkgs.lib.cleanSource self;
+
+            nativeBuildInputs = [ pkgs.installShellFiles ];
+            makeFlags = [ "PREFIX=$(out)" ];
+
+            doCheck = true;
+            checkTarget = "test";
+
+            postInstall = ''
+              installShellCompletion --cmd cbirds \
+                --bash <($out/bin/cbirds --completion bash) \
+                --zsh <($out/bin/cbirds --completion zsh) \
+                --fish <($out/bin/cbirds --completion fish)
+            '';
+
+            meta = {
+              description = "A flock of birds in your terminal";
+              homepage = "https://github.com/clainstone/cbirds";
+              license = pkgs.lib.licenses.mit;
+              mainProgram = "cbirds";
+              platforms = systems;
+            };
+          };
+        });
+    };
+}