diff --git a/addressbook.cabal b/addressbook.cabal
index ef0188e..00c35bc 100644
--- a/addressbook.cabal
+++ b/addressbook.cabal
@@ -42,6 +42,7 @@ library
                      , containers
                      , filepath
                      , parallel
+                     , unix
   hs-source-dirs:      src
   default-language:    Haskell2010
   ghc-options:         -Wall
diff --git a/default.nix b/default.nix
index 1431253..84a8668 100644
--- a/default.nix
+++ b/default.nix
@@ -1,7 +1,7 @@
 { mkDerivation, attoparsec, base, bytestring, conduit
 , conduit-extra, containers, criterion, filepath, hedgehog
 , hedgehog-corpus, HUnit, lens, lib, mtl, optparse-applicative
-, parallel, tasty, tasty-hedgehog, tasty-hunit, text, vector
+, parallel, tasty, tasty-hedgehog, tasty-hunit, text, unix, vector
 }:
 mkDerivation {
   pname = "addressbook";
@@ -11,7 +11,7 @@ mkDerivation {
   isExecutable = true;
   libraryHaskellDepends = [
     attoparsec base bytestring conduit conduit-extra containers
-    filepath lens mtl parallel text vector
+    filepath lens mtl parallel text unix vector
   ];
   executableHaskellDepends = [
     base bytestring containers criterion hedgehog-corpus
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..2e2c9f2
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,62 @@
+{
+  "nodes": {
+    "easy-hls": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1637250802,
+        "narHash": "sha256-/crlHEVB148PGQLZCsHOR9L5qgvCAfRSocIoKgmMAhA=",
+        "owner": "jkachmar",
+        "repo": "easy-hls-nix",
+        "rev": "7c123399ef8a67dc0e505d9cf7f2c7f64f1cd847",
+        "type": "github"
+      },
+      "original": {
+        "owner": "jkachmar",
+        "repo": "easy-hls-nix",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1637014545,
+        "narHash": "sha256-26IZAc5yzlD9FlDT54io1oqG/bBoyka+FJk5guaX4x4=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "bba5dcc8e0b20ab664967ad83d24d64cb64ec4f4",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1637312849,
+        "narHash": "sha256-OhVZopkyryEfLyPwcXk2IQsdi80lj6TY1YFoMNZ4hCQ=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e4806bb4416f88c20f8be0b8ef9b5b09ff9022a6",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "easy-hls": "easy-hls",
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..b077c73
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,53 @@
+{
+  description = "addressbook";
+
+  inputs = {
+    easy-hls = {
+      url = "github:jkachmar/easy-hls-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    flake-utils = {
+      url = "github:numtide/flake-utils";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, easy-hls }:
+    { overlay = final: prev: {
+        haskellPackages = prev.haskellPackages.override ( old: {
+          overrides = final.lib.composeExtensions (old.overrides or (_: _: {})) (f: p: {
+            addressbook = f.callPackage ./. {};
+          });
+        });
+      };
+    }
+    //
+    flake-utils.lib.eachSystem ["x86_64-linux" "x86_64-darwin"] ( system:
+      let
+        pkgs = import nixpkgs { inherit system; overlays = [ self.overlay ]; };
+        hp = pkgs.haskellPackages;
+        hls = (easy-hls.withGhcs [ hp.ghc ]).${system};
+      in
+      rec {
+
+        packages = { inherit (hp) addressbook; };
+
+        defaultPackage = packages.addressbook;
+        apps.addressbook = {
+          type = "app";
+          program = "${hp.addressbook}/bin/addressbook";
+        };
+        devShell = hp.shellFor {
+          packages = h: [h.addressbook];
+          withHoogle = true;
+          buildInputs = with pkgs; [
+            entr
+            cabal-install
+            hp.hlint
+            stylish-haskell
+            ghcid
+            hls
+          ];
+        };
+      }
+    );
+}
diff --git a/src/Control/Addressbook/Streaming.hs b/src/Control/Addressbook/Streaming.hs
index 59d1aca..856d11b 100644
--- a/src/Control/Addressbook/Streaming.hs
+++ b/src/Control/Addressbook/Streaming.hs
@@ -30,6 +30,7 @@ import System.IO.Unsafe (unsafeInterleaveIO)
 import Control.Parallel.Strategies (rseq, parMap)
 import qualified Data.List as L
 import Control.Monad (unless)
+import System.Posix (touchFile)
 
 combine :: (MonadUnliftIO m, MonadResource m, MonadThrow m, MonadIO m) => ConduitM FilePath Header m ()
 combine = await >>= \case
@@ -45,6 +46,7 @@ run :: IO ()
 run = do
   datDir <- fromMaybe "./" <$> lookupEnv "HOME"
   let datFile = datDir </> ".addressbook.dat"
+  touchFile datFile
   original <- Set.fromList . map LBS.toStrict . lbsLines <$> LBS.readFile datFile
   xs <- LBS.getContents >>= stream
   let set = original `Set.union` F.fold (parMap rseq F.fold (chunks 200 xs))