| Portability | portable |
|---|---|
| Stability | provisional |
| Maintainer | libraries@haskell.org |
System.Exit
Description
Exiting the program.
- data ExitCode
- exitWith :: ExitCode -> IO a
- exitFailure :: IO a
- exitSuccess :: IO a
Documentation
Defines the exit codes that a program can return.
Constructors
| ExitSuccess | indicates successful termination; |
| ExitFailure Int | indicates program failure with an exit code. The exact interpretation of the code is operating-system dependent. In particular, some values may be prohibited (e.g. 0 on a POSIX-compliant system). |
exitWith :: ExitCode -> IO aSource
Computation exitWith code throws ExitCode code.
Normally this terminates the program, returning code to the
program's caller.
On program termination, the standard Handles stdout and
stderr are flushed automatically; any other buffered Handles
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.
exitFailure :: IO aSource
The computation exitFailure is equivalent to
exitWith (ExitFailure exitfail),
where exitfail is implementation-dependent.
exitSuccess :: IO aSource
The computation exitSuccess is equivalent to
exitWith ExitSuccess, It terminates the program
successfully.