1 -----------------------------------------------------------------------------
3 -- Module : System.Exit
4 -- Copyright : (c) The University of Glasgow 2001
5 -- License : BSD-style (see the file libraries/base/LICENSE)
7 -- Maintainer : libraries@haskell.org
8 -- Stability : provisional
9 -- Portability : portable
11 -- Exiting the program.
13 -----------------------------------------------------------------------------
17 ExitCode(ExitSuccess,ExitFailure)
18 , exitWith -- :: ExitCode -> IO a
19 , exitFailure -- :: IO a
20 , exitSuccess -- :: IO a
25 #ifdef __GLASGOW_HASKELL__
30 import Hugs.Prelude (ExitCode(..))
31 import Control.Exception.Base
41 -- ---------------------------------------------------------------------------
44 -- | Computation 'exitWith' @code@ throws 'ExitException' @code@.
45 -- Normally this terminates the program, returning @code@ to the
46 -- program's caller. Before the program terminates, any open or
47 -- semi-closed handles are first closed.
49 -- A program that fails in any other way is treated as if it had
50 -- called 'exitFailure'.
51 -- A program that terminates successfully without calling 'exitWith'
52 -- explicitly is treated as it it had called 'exitWith' 'ExitSuccess'.
54 -- As an 'ExitException' is not an 'IOError', 'exitWith' bypasses
55 -- the error handling in the 'IO' monad and cannot be intercepted by
56 -- 'catch' from the "Prelude". However it is an 'Exception', and can
57 -- be caught using the functions of "Control.Exception". This means
58 -- that cleanup computations added with 'Control.Exception.bracket'
59 -- (from "Control.Exception") are also executed properly on 'exitWith'.
61 -- Note: in GHC, 'exitWith' should be called from the main program
62 -- thread in order to exit the process. When called from another
63 -- thread, 'exitWith' will throw an 'ExitException' as normal, but the
64 -- exception will not cause the process itself to exit.
67 exitWith :: ExitCode -> IO a
68 exitWith ExitSuccess = throwIO ExitSuccess
69 exitWith code@(ExitFailure n)
70 | n /= 0 = throwIO code
71 #ifdef __GLASGOW_HASKELL__
72 | otherwise = ioError (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing Nothing)
74 #endif /* ! __NHC__ */
76 -- | The computation 'exitFailure' is equivalent to
77 -- 'exitWith' @(@'ExitFailure' /exitfail/@)@,
78 -- where /exitfail/ is implementation-dependent.
80 exitFailure = exitWith (ExitFailure 1)
82 -- | The computation 'exitSuccess' is equivalent to
83 -- 'exitWith' 'ExitSuccess', It terminates the program
86 exitSuccess = exitWith ExitSuccess