Add nix flake support

README.md

@@ -2,6 +2,13 @@
 
 Repository of lists of one-liners to use as a message-of-the-day.
 
-`boi-rebirth-fortunes.txt` is taken from The Binding of Isaac: Rebirth.
+## flake
+
+The defaultPackage output of this repository's flake is a derivation containing the motd files in this repository.
+
+## sources
+
+* `boi-rebirth-fortunes.txt` is taken from the Fortune Telling Machine messages from The Binding of Isaac: Rebirth.
+
+* `40k-thought-for-the-day.txt` is sourced from 40k Lexicanum.
 
-`40k-thought-for-the-day.txt` is sourced from 40k Lexicanum.

flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1638122382,
+        "narHash": "sha256-sQzZzAbvKEqN9s0bzWuYmRaA03v40gaJ4+iL1LXjaeI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "74f7e4319258e287b0f9cb95426c9853b282730b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1640223855,
+        "narHash": "sha256-2bOGDrou/P0E85O5CzcZcHrvDBR78kRIwSPMlaLnFb8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e7f5c0a08e442ed5772852b9f832d5d716020ebf",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,36 @@
+{
+  description = "A flake of MOTD files.";
+
+  inputs.nixpkgs.url = github:NixOS/nixpkgs;
+  inputs.flake-utils.url = github:numtide/flake-utils;
+
+  outputs = { self, nixpkgs, flake-utils }:
+    let
+      motdFiles = {
+        "40k" = ./40k-thought-for-the-day.txt;
+        rebirth = ./boi-rebirth-fortunes.txt;
+      };
+    in
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        motd = pkgs.stdenv.mkDerivation {
+          pname = "motd";
+          version = "1.0";
+          builder = builtins.toFile "motd-builder.sh" ''
+            source $stdenv/setup
+            mkdir -p $out
+            ${builtins.foldl'
+              (a: b: "${a}\n${b}")
+              ""
+              (map
+                (attr: "cp ${motdFiles.${attr}} $out/${attr}.txt")
+                (builtins.attrNames motdFiles))}
+          '';
+        };
+      in
+      {
+        defaultPackage = motd;
+      }
+    );
+}