diff --git a/addressbook.cabal b/addressbook.cabal
index 1d10838..76cc497 100644
--- a/addressbook.cabal
+++ b/addressbook.cabal
@@ -36,6 +36,7 @@ library
                      , bytestring-trie
                      , vector
                      , containers
+                     , filepath
   hs-source-dirs:      src
   default-language:    Haskell2010
   ghc-options:         -Wall
diff --git a/src/Control/Addressbook/Streaming.hs b/src/Control/Addressbook/Streaming.hs
index b209773..9e247da 100644
--- a/src/Control/Addressbook/Streaming.hs
+++ b/src/Control/Addressbook/Streaming.hs
@@ -5,6 +5,7 @@ import qualified Data.Text as T
 import Conduit
 import qualified Data.Conduit.Binary as CB
 import qualified Data.Conduit.Combinators as C
+import qualified Data.Conduit.List as CL
 import qualified Data.Conduit.Text as CT
 
 import Data.Email
@@ -16,7 +17,14 @@ import System.IO
 
 import qualified Data.Foldable as F
 
-import qualified Data.Set as S
+import qualified Data.Trie as Trie
+
+import Data.Maybe
+       (fromMaybe)
+import System.Environment
+       (lookupEnv)
+import System.FilePath
+       ((</>))
 
 combine :: (MonadUnliftIO m, MonadResource m, MonadThrow m, MonadIO m) => ConduitM FilePath Header m ()
 combine = await >>= \case
@@ -25,8 +33,10 @@ combine = await >>= \case
 
 run :: IO ()
 run = do
-  x <- runResourceT $ runConduit stream
-  F.for_ x print
+  datDir <- fromMaybe "./" <$> lookupEnv "HOME"
+  runResourceT $ do
+    x <- runConduit stream
+    runConduit (CL.sourceList (Trie.keys x) .| C.map (<> "\n") .| CB.sinkFileCautious (datDir </> ".addressbook.dat"))
   where
     separate = \case
       From x -> [x]
@@ -38,4 +48,5 @@ run = do
         .| C.map T.unpack
         .| combine
         .| C.concatMap separate
-        .| C.foldMap (S.singleton)
+        .| CT.encode CT.utf8
+        .| C.foldMap (`Trie.singleton` ())