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{-# LANGUAGE CPP #-}
module Utility.Inotify where
import Common hiding (isDirectory)
import System.INotify
import qualified System.Posix.Files as Files
import System.Posix.Terminal
import Control.Concurrent.MVar
import System.Posix.Signals
demo :: IO ()
demo = withINotify $ \i -> do
watchDir i add del "/home/joey/tmp/me"
putStrLn "started"
waitForTermination
where
add file = putStrLn $ "add " ++ file
del file = putStrLn $ "del " ++ file
{- Watches for changes to files in a directory, and all its subdirectories,
- using inotify. This function returns after its initial setup is
- complete, leaving a thread running. Then callbacks are made for adding
- and deleting files.
-
- Inotify is weak at recursive directory watching; the whole directory
- tree must be walked and watches set explicitly for each subdirectory.
-
- To notice newly created subdirectories, inotify is used, and
- watches are registered for those directories. There is a race there;
- things can be added to a directory before the watch gets registered.
-
- To close the inotify race, each time a new directory is found, it also
- recursively scans it, assuming all files in it were just added,
- and registering each subdirectory.
-
- Note: Due to the race amelioration, multiple add events may occur
- for the same file.
-
- Note: Moving a file may involve deleting it from its old location and
- adding it to the new location.
-
- Note: Modification of files is not detected, and it's assumed that when
- a file that was open for write is closed, it's done being written
- to, and can be added.
-
- Note: inotify has a limit to the number of watches allowed,
- /proc/sys/fs/inotify/max_user_watches (default 8192).
- So This will fail if there are too many subdirectories.
-}
watchDir :: INotify -> (FilePath -> IO ()) -> (FilePath -> IO ()) -> FilePath -> IO ()
watchDir i add del dir = watchDir' False i add del dir
watchDir' :: Bool -> INotify -> (FilePath -> IO ()) -> (FilePath -> IO ()) -> FilePath -> IO ()
watchDir' scan i add del dir = do
_ <- addWatch i [MoveIn, MoveOut, Create, Delete, CloseWrite] dir go
_ <- mapM walk =<< dirContents dir
return ()
where
recurse = watchDir' scan i add del
walk f = ifM (catchBoolIO $ Files.isDirectory <$> getFileStatus f)
( recurse f
, if scan then add f else return ()
)
a <@> f = a $ dir </> f
go (Created { isDirectory = False }) = return ()
go (Created { filePath = subdir }) = recurse <@> subdir
go (Closed { maybeFilePath = Just f }) = add <@> f
go (MovedIn { isDirectory = False, filePath = f }) = add <@> f
go (MovedOut { isDirectory = False, filePath = f }) = del <@> f
go (Deleted { isDirectory = False, filePath = f }) = del <@> f
go _ = return ()
{- Pauses the main thread, letting children run until program termination. -}
waitForTermination :: IO ()
waitForTermination = do
mv <- newEmptyMVar
check softwareTermination mv
whenM (queryTerminal stdInput) $
check keyboardSignal mv
takeMVar mv
where
check sig mv = do
_ <- installHandler sig (CatchOnce $ putMVar mv ()) Nothing
return ()
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