Haskell - exit program with specified error code
In Haskell, is there a way to exit the program with the specified error code? The resources I've read usually point to a function error
to exit a program with an error, but it always exits with an error code 1
.
[martin@localhost Haskell]$ cat error.hs
main = do
error "My English language error message"
[martin@localhost Haskell]$ ghc error.hs
[1 of 1] Compiling Main ( error.hs, error.o )
Linking error ...
[martin@localhost Haskell]$ ./error
error: My English language error message
[martin@localhost Haskell]$ echo $?
1
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1 answer
Use exitWith
from System.Exit
:
main = exitWith (ExitFailure 2)
I would add a few helpers for convenience:
exitWithErrorMessage :: String -> ExitCode -> IO a
exitWithErrorMessage str e = hPutStrLn stderr str >> exitWith e
exitResourceMissing :: IO a
exitResourceMissing = exitWithErrorMessage "Resource missing" (ExitFailure 2)
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