Dear GHC team,
I am testing the IO operations of GHC with the Unix named pipes
(in ghc-7.01 under Debian Linux).
In the below example,
the pipe pair are created by > mkfifo toA
> mkfifo fromA,
`main' in Main.hs opens toA for writing,
opens fromA for reading,
outputs "A1" to toA.
The C program fifo2 opens toA for reading,
opens fromA for writing,
inputs a string from toA,
prints "done" to the screen
(fromA is not really used, but will be needed in future).
The effect is that fifo2 (on terminal-2) hangs silent, while
Main.hs (on terminal-1) does its part.
If I remove the fopen(..fromA..)
call in fifo2.c, then it runs as expected
(after this example is fixed, fifo2 will need to write to fromA).
Main.hs is built by ghc --make Main,
The C program is built by gcc -o fifo2 fifo2.c
First, ./fifo2 is run on terminal-2,
then ./Main is run on terminal-1.
The source is quite small:
-- Main.hs ---------------------------------------------------------
import System.IO (IOMode(..), IO(..), Handle, openFile, hPutStr,
hFlush)
dir = showString "/home/mechvel/ghc/notes/npipe/"
toA_IO = openFile (dir "toA") WriteMode :: IO Handle
fromA_IO = openFile (dir "fromA") ReadMode
axiomIO :: Handle -> String -> IO()
axiomIO h str = do
hPutStr h str
hFlush h
putStr "hFlush done\n"
main = do
h <- toA_IO
putStr "str1 --> "
axiomIO h "A1\n"
----------------------- fifo2.c -------------------------------------
#include