main.hs

module Main where

import Control.Concurrent

import System.Posix.Signals

signalsDebugFile :: String
signalsDebugFile = "signals.out"

handleUSR1 :: IO ()
handleUSR1 =
  appendFile signalsDebugFile "Got USR1\n"

handleUSR2 :: IO ()
handleUSR2 =
  appendFile signalsDebugFile "Got USR2\n"

handleINT :: IO ()
handleINT =
  appendFile signalsDebugFile "Got INT\n"

handleTERM :: MVar () -> IO ()
handleTERM mvar =
  appendFile signalsDebugFile "Got TERM\n" >>
  putMVar mvar ()

main :: IO ()
main = do
  mvar <- newEmptyMVar
  forkIO (daemon mvar)
  readMVar mvar

daemon :: MVar () -> IO ()
daemon mvar =
  do
    installHandler userDefinedSignal1 ( Catch handleUSR1 ) Nothing
    installHandler userDefinedSignal2 ( Catch handleUSR2 ) Nothing
    installHandler keyboardSignal ( Catch handleINT ) Nothing
    installHandler softwareTermination ( Catch (handleTERM mvar) ) Nothing
    unblockSignals fullSignalSet
    -- block forever without spinning the CPU
    newEmptyMVar >>= readMVar