testing file locking

filelocktest.hs

import Control.Concurrent
import System.IO
import System.Posix.Files 
import System.Posix.IO 
import System.Posix.Types

main = do 
    putStrLn "file lock test" 
    let fp = "test.txt"
    fd <- openFd fp ReadWrite mode defaultFileFlags
    r <- getLock fd (ReadLock,AbsoluteSeek,0,0) 
    case r of 
      Nothing -> do 
        putStrLn "Nothing"
        setLock fd (WriteLock,AbsoluteSeek,0,0)
      Just _ -> putStrLn "Just _"
    threadDelay 50000000
    closeFd fd 
  where mode = Just (unionFileModes ownerReadMode ownerWriteMode)