handling sigINT and sigTERM in Haskell (posix)

SigInt.hs

module Main where

import Control.Concurrent (threadDelay, MVar, newEmptyMVar, putMVar, tryTakeMVar)

import Data.Maybe (isJust)

import System.IO (hSetBuffering, BufferMode(NoBuffering), stdout)
import System.Posix.Signals (installHandler, Handler(Catch), sigINT, sigTERM)


main :: IO ()
main = do
  stop <- newEmptyMVar
  hSetBuffering stdout NoBuffering
  _ <- installHandler sigINT (Catch $ onSigInt stop) Nothing
  _ <- installHandler sigTERM (Catch $ onSigTerm stop) Nothing
  loop stop


loop :: MVar () -> IO ()
loop stop = do
  stopRequested <- isJust <$> tryTakeMVar stop
  if stopRequested
    then putStrLn "bye!"
    else do
      threadDelay 1000000
      putStr "."
      loop stop
  


onSigInt :: MVar () -> IO ()
onSigInt stop = do
  putStrLn "got sigINT"
  putMVar stop ()


onSigTerm :: MVar () -> IO ()
onSigTerm stop = do
  putStrLn "got sigTERM"
  putMVar stop ()