Allow interrupting commands with Ctrl-C. Catch exceptions throw by commands.

src/GF/System/Signal.hs

@@ -0,0 +1,47 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : GF.System.Signal
+-- Maintainer  : Bjorn Bringert
+-- Stability   : (stability)
+-- Portability : (portability)
+--
+-- > CVS $Date: 2005/11/07 20:15:05 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.1 $
+--
+-- Allows SIGINT (Ctrl-C) to interrupt computations.
+-----------------------------------------------------------------------------
+
+module GF.System.Signal where
+
+import Control.Concurrent (myThreadId, killThread)
+import Control.Exception (Exception,catch)
+import Prelude hiding (catch)
+import System.IO
+import System.Posix.Signals
+
+-- | Run an IO action, and allow it to be interrupted
+--   by a SIGINT to the current process. Returns
+--   an exception if the process did not complete 
+--   normally.
+--   NOTES: 
+--   * This will replace any existing SIGINT
+--     handlers, and after the computation has completed
+--     the default handler will be installed for SIGINT.
+--   * If the IO action is lazy (e.g. using readFile,
+--     unsafeInterleaveIO etc.) the lazy computation will
+--     not be interruptible, as it will be performed
+--     after the signal handler has been removed.
+runInterruptibly :: IO a -> IO (Either Exception a)
+runInterruptibly a = do t <- myThreadId
+                        installHandler sigINT (Catch (killThread t)) Nothing
+                        x <- p `catch` h
+                        installHandler sigINT Default Nothing
+                        return x
+  where p = a >>= \x -> return $! Right $! x
+        h e = return $ Left e
+
+-- | Like 'runInterruptibly', but always returns (), whether
+--   the computation fails or not.
+runInterruptibly_ :: IO () -> IO ()
+runInterruptibly_ = fmap (either (const ()) id) . runInterruptibly