diff --git a/src/Main.hs b/src/Main.hs
index af31a6d..ced6c16 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -6,10 +6,17 @@ import qualified Data.Text.IO as T
 import Data.Text.Prettyprint.Doc (pretty)
 import Text.Megaparsec (parse)
 import Windows12.Parser (programP)
+import System.Environment (getArgs)
 
 main :: IO ()
 main = do
-  test <- T.readFile "test/hello.w12"
-  case parse programP "test/hello.w12" test of
-    Left err -> print err
-    Right ast -> print (pretty ast)
+  args <- getArgs
+
+  if length args /= 2
+    then putStrLn "Usage: windows12 <input file> <output file>"
+    else do
+      let [inputFile, outputFile] = args
+      test <- T.readFile inputFile
+      case parse programP inputFile test of
+        Left err -> print err
+        Right ast -> print (pretty ast)