diff -r 258bef08b31e -r 30f6e8d2cd96 src/Tools/Haskell/Haskell.thy
--- a/src/Tools/Haskell/Haskell.thy	Sat Nov 10 14:08:02 2018 +0100
+++ b/src/Tools/Haskell/Haskell.thy	Sat Nov 10 16:32:00 2018 +0100
@@ -516,6 +516,39 @@
 no_output = ("", "")
 \<close>
 
+generate_haskell_file "File.hs" = \<open>
+{-  Title:      Tools/Haskell/File.hs
+    Author:     Makarius
+    LICENSE:    BSD 3-clause (Isabelle)
+
+File-system operations
+-}
+
+module Isabelle.File (setup, read, write, append) where
+
+import Prelude hiding (read)
+import System.IO (IO)
+import qualified System.IO as IO
+
+setup :: IO.Handle -> IO ()
+setup h = do
+  IO.hSetEncoding h IO.utf8
+  IO.hSetNewlineMode h IO.noNewlineTranslation
+
+read :: IO.FilePath -> IO String
+read path =
+  IO.withFile path IO.ReadMode (\h ->
+    do setup h; IO.hGetContents h >>= \s -> length s `seq` return s)
+
+write :: IO.FilePath -> String -> IO ()
+write path s =
+  IO.withFile path IO.WriteMode (\h -> do setup h; IO.hPutStr h s)
+
+append :: IO.FilePath -> String -> IO ()
+append path s =
+  IO.withFile path IO.AppendMode (\h -> do setup h; IO.hPutStr h s)
+\<close>
+
 generate_haskell_file "XML.hs" = \<open>
 {-  Title:      Tools/Haskell/XML.hs
     Author:     Makarius