{-# 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 ) where import Prelude 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 it it had called 'exitWith' 'ExitSuccess'. -- -- As an 'ExitCode' is not an 'IOError', 'exitWith' bypasses -- the error handling in the 'IO' monad and cannot be intercepted by -- 'catch' from the "Prelude". However it is a 'SomeException', and 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 'ExitException' as normal, but the -- exception will not cause the process itself to exit. -- exitWith :: ExitCode -> IO a exitWith ExitSuccess = throwIO ExitSuccess exitWith code@(ExitFailure n) | n /= 0 = throwIO code | otherwise = ioError (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing Nothing) -- | The computation 'exitFailure' is equivalent to -- 'exitWith' @(@'ExitFailure' /exitfail/@)@, -- where /exitfail/ is implementation-dependent. exitFailure :: IO a exitFailure = exitWith (ExitFailure 1) -- | The computation 'exitSuccess' is equivalent to -- 'exitWith' 'ExitSuccess', It terminates the program -- successfully. exitSuccess :: IO a exitSuccess = exitWith ExitSuccess