Hi,
Why doesn't this program start reading from one fifo until the second
fifo
gets opened (with cat), too? (It doesn't matter which fifo is opened
first.)
Why doesn't it print "forked" before "fifo1" is opened?
After both fifos are open, it works as expected.
I have ghc 6.6-3 on debian-linux (testing)
Sebastian Setzer
------------------------------------------------------------------
-- Compile: ghc twofifo.hs -o twofifo -threaded -package unix-1.0
-- Usage:
-- mkfifo fifo1
-- mkfifo fifo1
-- ./twofifo
-- in two separate xterms:
-- cat > fifo1
-- ...
-- cat > fifo2
-- ...
import System.IO
import System.Posix.IO
import System.Posix.Types
import Control.Concurrent
main :: IO()
main = do
f1Thread <- forkOS (openAndShowFile "fifo1")
print "forked"
hFlush stdout
openAndShowFile "fifo2"
openAndShowFile :: String -> IO()
openAndShowFile name = do
fd <- openFd name ReadOnly Nothing defaultFileFlags
showFile name fd
showFile :: String -> Fd -> IO()
showFile name fd = do
threadWaitRead fd
(s, count) <- fdRead fd 1024
print (name ++ ": " ++ s)
hFlush stdout
showFile name fd
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