content: -- !!! test multiple-reader single-writer locking semantics
  
  import System.IO
  import System.IO.Error
  
  file1 = "openFile005.out1"
  file2 = "openFile005.out2"
  
  main = do
    putStrLn "two writes (should fail)"
    h <- openFile file1 WriteMode
    tryIOError (openFile file1 WriteMode) >>= print
    hClose h
  
    putStrLn "write and an append (should fail)"
    h <- openFile file1 WriteMode
    tryIOError (openFile file1 AppendMode) >>= print
    hClose h
  
    putStrLn "read/write and a write (should fail)"
    h <- openFile file1 ReadWriteMode
    tryIOError (openFile file1 WriteMode) >>= print
    hClose h
  
    putStrLn "read and a read/write (should fail)"
    h <- openFile file1 ReadMode
    tryIOError (openFile file1 ReadWriteMode) >>= print
    hClose h
  
    putStrLn "write and a read (should fail)"
    h <- openFile file1 WriteMode
    tryIOError (openFile file1 ReadMode) >>= print
    hClose h
  
    putStrLn "two writes, different files (silly, but should succeed)"
    h1 <- openFile file1 WriteMode
    h2 <- openFile file2 WriteMode
    hClose h1
    hClose h2
  
    putStrLn "two reads, should succeed"
    h1 <- openFile file1 ReadMode
    h2 <- openFile file1 ReadMode
    hClose h1
    hClose h2
  