diff --git a/examples/getObj.hs b/examples/getObj.hs
index a758179..778d989 100644
--- a/examples/getObj.hs
+++ b/examples/getObj.hs
@@ -4,16 +4,17 @@ import Codec.Compression.Zlib (decompress)
 import Data.ByteString.Lazy.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as BS (readFile)
 import qualified Data.ByteString.Lazy.Char8 as Lazy (fromStrict, putStr, toStrict)
-import Data.Map ((!))
-import qualified Data.Map as Map (lookup)
+import Data.Map ((!?))
+import qualified Data.Map as Map (keys, lookup)
 import PDF (Document(..), parseDocument)
 import qualified PDF.EOL as EOL (Style)
 import PDF.Object (Content(..), DirectObject(..), Object(..), Name(..))
 import PDF.Output (ObjectId(..))
 import qualified PDF.Output as Output (render)
 import PDF.Update (unify)
-import System.Environment (getArgs)
-import System.IO (hPutStrLn, stderr)
+import System.Environment (getArgs, getProgName)
+import System.Exit (die)
+import Text.Printf (printf)
 
 display :: EOL.Style -> Object -> ByteString
 display eolStyle d@(Direct _) = Output.render eolStyle d
@@ -25,16 +26,28 @@ display eolStyle s@(Stream {header, streamContent}) = Output.render eolStyle $
       }
     _ -> s
 
-extractObject :: ObjectId -> Document -> ByteString
+extractObject :: ObjectId -> Document -> Either String ByteString
 extractObject objectId (Document {eolStyle, updates}) =
-  display eolStyle . (!objectId) $ objects  content
+  case objects content !? objectId of
+    Nothing -> Left $ "No object has ID " ++ show (getObjectId objectId)
+    Just o -> Right $ display eolStyle o
   where
     content = unify updates
 
+listObjectIds :: Document -> Either String [String]
+listObjectIds =
+  Right . prependTitle . toString . Map.keys . objects . unify . updates
+  where
+    toString = fmap (show . getObjectId)
+    prependTitle = ("ObjectIds defined in this PDF:":)
+
 main :: IO ()
 main = do
-  [inputFile, objectId] <- getArgs
-  result <- parseDocument <$> BS.readFile inputFile
-  case result of
-    Left parseError -> hPutStrLn stderr parseError
-    Right doc -> Lazy.putStr $ extractObject (ObjectId (read objectId)) doc
+  (inputFile, getData) <- parse =<< getArgs
+  input <- BS.readFile inputFile
+  either die id $ (parseDocument input >>= getData)
+  where
+    parse [inputFile] = return (inputFile, fmap (mapM_ putStrLn) . listObjectIds)
+    parse [inputFile, objectId] = return
+      (inputFile, fmap Lazy.putStr . extractObject (ObjectId (read objectId)))
+    parse _ = die . printf "Syntax: %s inputFile [OBJECT_ID]\n" =<< getProgName