On 12 December 2005 17:53, Donn Cave wrote:

Quoth Einar Karttunen : ...

...

*** Exception: z: openFile: resource busy (file is locked)

Now that I have access to a platform where ghc builds, I can duplicate your results - and in case it helps, here's another work-around. Apparently this "feature" uses POSIX filesystem locks, because it appears that we can exploit the brain-damaged semantics of that system: when a process closes a file, all its locks are cleared - whether they were acquired through that file descriptor or another unrelated open. It may be the first time anyone has ever benefited from this!

import IO

main = do fc <- openFile "z" ReadMode -- sacrificial handle fr <- openFile "z" ReadMode hClose fc fa <- openFile "z" AppendMode hPutStr fa "append this line\n" hGetLine fr >>= print

If you may need to open more read handles later, you can add another extra close after the append handle.

Thank you (I suppose :-) for exposing a bug in GHC's file locking. It doesn't have anything to do with POSIX filesystem locks, FWIW, it's just a bug, in some very old code. Cheers, Simon