Quoth "Serge D. Mechveliani"
(I wonder: is this for beginners@haskell.org ?)
No, not really! As already mentioned, the use of UnsafePerformIO goes a little beyond what I think is its intended purpose, and I think you might have better luck here with a test program that illustrates the problem and doesn't depend on that. But while you're looking into that ... you might be interested to know that there's a problem with named pipes in GHC (beyond the problems that afflict anyone who tries to work with named pipes.) GHC I/O routinely sets file descriptors to non-blocking, unlike the IO libraries for C and other languages, and this could add to your troubles with named pipes. You can read up on that and possibly find clues to the present problem. Donn