    {-# LANGUAGE Trustworthy #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  System.Exit
    -- Copyright   :  (c) The University of Glasgow 2001
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  provisional
    -- Portability :  portable
    --
    -- Exiting the program.
    --
    -----------------------------------------------------------------------------

    module System.Exit
        (
          ExitCode(ExitSuccess,ExitFailure)
        , exitWith
        , exitFailure
        , exitSuccess
        , die
      ) where

    import System.IO

    import GHC.IO
    import GHC.IO.Exception

    -- ---------------------------------------------------------------------------
    -- exitWith

    -- | Computation 'exitWith' @code@ throws 'ExitCode' @code@.
    -- Normally this terminates the program, returning @code@ to the
    -- program's caller.
    --
    -- On program termination, the standard 'Handle's 'stdout' and
    -- 'stderr' are flushed automatically; any other buffered 'Handle's
    -- need to be flushed manually, otherwise the buffered data will be
    -- discarded.
    --
    -- A program that fails in any other way is treated as if it had
    -- called 'exitFailure'.
    -- A program that terminates successfully without calling 'exitWith'
    -- explicitly is treated as if it had called 'exitWith' 'ExitSuccess'.
    --
    -- As an 'ExitCode' is an 'Control.Exception.Exception', it can be
    -- caught using the functions of "Control.Exception".  This means that
    -- cleanup computations added with 'Control.Exception.bracket' (from
    -- "Control.Exception") are also executed properly on 'exitWith'.
    --
    -- Note: in GHC, 'exitWith' should be called from the main program
    -- thread in order to exit the process.  When called from another
    -- thread, 'exitWith' will throw an 'ExitCode' as normal, but the
    -- exception will not cause the process itself to exit.
    --
    exitWith :: ExitCode -> IO a
    exitWith :: forall a. ExitCode -> IO a
    exitWith ExitCode
    ExitSuccess = ExitCode -> IO a
    forall e a. Exception e => e -> IO a
    throwIO ExitCode
    ExitSuccess
    exitWith code :: ExitCode
    code@(ExitFailure Int
    n)
      | Int
    n Int -> Int -> Bool
    forall a. Eq a => a -> a -> Bool
    /= Int
    0 = ExitCode -> IO a
    forall e a. Exception e => e -> IO a
    throwIO ExitCode
    code
      | Bool
    otherwise = IOError -> IO a
    forall a. IOError -> IO a
    ioError (Maybe Handle
    -> IOErrorType
    -> String
    -> String
    -> Maybe CInt
    -> Maybe String
    -> IOError
    IOError Maybe Handle
    forall a. Maybe a
    Nothing IOErrorType
    InvalidArgument String
    "exitWith" String
    "ExitFailure 0" Maybe CInt
    forall a. Maybe a
    Nothing Maybe String
    forall a. Maybe a
    Nothing)

    -- | The computation 'exitFailure' is equivalent to
    -- 'exitWith' @(@'ExitFailure' /exitfail/@)@,
    -- where /exitfail/ is implementation-dependent.
    exitFailure :: IO a
    exitFailure :: forall a. IO a
    exitFailure = ExitCode -> IO a
    forall a. ExitCode -> IO a
    exitWith (Int -> ExitCode
    ExitFailure Int
    1)

    -- | The computation 'exitSuccess' is equivalent to
    -- 'exitWith' 'ExitSuccess', It terminates the program
    -- successfully.
    exitSuccess :: IO a
    exitSuccess :: forall a. IO a
    exitSuccess = ExitCode -> IO a
    forall a. ExitCode -> IO a
    exitWith ExitCode
    ExitSuccess

    -- | Write given error message to `stderr` and terminate with `exitFailure`.
    --
    -- @since 4.8.0.0
    die :: String -> IO a
    die :: forall a. String -> IO a
    die String
    err = Handle -> String -> IO ()
    hPutStrLn Handle
    stderr String
    err IO () -> IO a -> IO a
    forall a b. IO a -> IO b -> IO b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> IO a
    forall a. IO a
    exitFailure