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|
{- daemon support
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.Daemon where
import Common
import System.Posix
{- Run an action as a daemon, with all output sent to a file descriptor.
-
- Can write its pid to a file, to guard against multiple instances
- running and allow easy termination.
-
- When successful, does not return. -}
daemonize :: Fd -> Maybe FilePath -> Bool -> IO () -> IO ()
daemonize logfd pidfile changedirectory a = do
_ <- forkProcess child1
out
where
child1 = do
_ <- createSession
_ <- forkProcess child2
out
child2 = do
maybe noop lockPidFile pidfile
when changedirectory $
setCurrentDirectory "/"
nullfd <- openFd "/dev/null" ReadOnly Nothing defaultFileFlags
_ <- redir nullfd stdInput
mapM_ (redir logfd) [stdOutput, stdError]
closeFd logfd
a
out
redir newh h = do
closeFd h
dupTo newh h
out = exitImmediately ExitSuccess
lockPidFile :: FilePath -> IO ()
lockPidFile file = void $ do
fd <- openFd file ReadWrite (Just stdFileMode) defaultFileFlags
catchIO
(setLock fd (WriteLock, AbsoluteSeek, 0, 0))
(const $ error "Daemon is already running.")
fdWrite fd =<< show <$> getProcessID
|
