module Daemon where import System Directory import System Exit import

module Daemon where

import System.Directory
import System.Exit
import System.Posix.Files
import System.Posix.IO
import System.Posix.Process
import System.Posix.Signals

daemonize :: IO () -> IO ()
daemonize f = do
  omask <- setFileCreationMask 0
  pid <- forkProcess child
  exitSuccess

  where

    child :: IO ()
    child = do
      sess <- createSession
      ohandler <- installHandler sigHUP Ignore Nothing
      forkProcess grandChild
      exitSuccess

    grandChild :: IO ()
    grandChild = do
      setCurrentDirectory "/"
      devNullFd <- openFd "/dev/null" ReadWrite Nothing defaultFileFlags
      mapM_ (closeAndDupTo devNullFd) [stdInput, stdOutput, stdError]
      f
      where
        closeAndDupTo dupFd fd = closeFd fd >> dupTo dupFd fd