Re: `Expect'-like lazy reading/Parsec matching on TCP sockets
Ooops! It seems that this doesn't behave well with a -threaded RTS. I get an EOF on handles that I know for a fact shouldn't be receiving them. It still works well without -threaded, but does anyone know why I'm getting this behavior? hGetContentsTimeout :: Handle -> Int -> IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready <- hWaitForInput h t if (not ready) then return [] else do c <- hGetChar h s <- unsafeInterleaveIO (hGetContentsTimeout h t) return (c:s) (I did add EOF checking, but all that did was return the end of the list earlier than I wanted)
Hello Scott, Friday, April 6, 2007, 11:44:01 PM, you wrote: you should write compiler version and OS for such problems. if it's 6.6 and Win, try to upgrade to current STABLE build: smth like http://www.haskell.org/ghc/dist/stable/dist/ghc-6.6.20061207-i386-unknown-mi... but newer (this one is dec 12 build) I/O in Windows threaded RTS was fixed after initial 6.6 release and afaik hWaitForInput should work better now. alternatively, you can try with hand-made timeout solution
Ooops! It seems that this doesn't behave well with a -threaded RTS. I get an EOF on handles that I know for a fact shouldn't be receiving them. It still works well without -threaded, but does anyone know why I'm getting this behavior?
hGetContentsTimeout :: Handle -> Int -> IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready <- hWaitForInput h t if (not ready) then return [] else do c <- hGetChar h s <- unsafeInterleaveIO (hGetContentsTimeout h t) return (c:s)
(I did add EOF checking, but all that did was return the end of the list earlier than I wanted)
-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com
On Fri, Apr 06, 2007 at 01:44:01PM -0600, Scott Bell wrote:
Ooops! It seems that this doesn't behave well with a -threaded RTS. I get an EOF on handles that I know for a fact shouldn't be receiving them. It still works well without -threaded, but does anyone know why I'm getting this behavior?
hGetContentsTimeout :: Handle -> Int -> IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready <- hWaitForInput h t if (not ready) then return [] else do c <- hGetChar h s <- unsafeInterleaveIO (hGetContentsTimeout h t) return (c:s)
(I did add EOF checking, but all that did was return the end of the list earlier than I wanted)
Have you got a complete (but preferably small) program showing the problem? Thanks Ian
Have you got a complete (but preferably small) program showing the problem?
Ian, Here is the source and behavior that I'm seeing (Linux x86, under both 6.6 and 6.7-20070404: module Main where import System.IO import System.IO.Unsafe import System.Process import Text.ParserCombinators.Parsec main :: IO () main = do (_, h, _, p) <- runInteractiveCommand "telnet nyx.nyx.net" t <- hGetContentsTimeout h 15000 print t >> terminateProcess p hGetContentsTimeout :: Handle -> Int -> IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready <- hWaitForInput h t; eof <- hIsEOF h if ((not ready) || eof) then return [] else do c <- hGetChar h s <- unsafeInterleaveIO (hGetContentsTimeout h t) return (c:s) -- Behavior with threaded RTS, string is returned early because of EOF: sebell@drei:~/src/remote$ ghc --make Remote.hs -o remote -threaded [1 of 1] Compiling Main ( Remote.hs, Remote.o ) Linking remote ... sebell@drei:~/src/remote$ ./remote "Trying 206.124.29.1...\nConnected to nyx.nyx.net.\nEscape character is '^]'.\n" -- Behavior with non-threaded RTS, proper timeout is observed: sebell@drei:~/src/remote$ ./remote "Trying 206.124.29.1...\nConnected to nyx.nyx.net.\nEscape character is '^]'.\n\n\n Welcome to Nyx, The Spirit of the Night\n (303) 409-1401\n nyx.nyx.net -- 206.124.29.1\n nyx10.nyx.net -- 206.124.29.2\n\n Free Public Internet Access\n\n ===========================\n New user? Login as new\n ===========================\n\n (If you get timed out, try later. Nyx would be too slow to use.)\n\n\n\n\r\n\r\nSunOS UNIX (nyx)\r\n\r\r\n\rlogin: "
Hi Scott, On Mon, Apr 09, 2007 at 10:03:55AM -0600, Scott Bell wrote:
Have you got a complete (but preferably small) program showing the problem?
Great example, thanks! Sorry for the delay in tracking it down.
main :: IO () main = do (_, h, _, p) <- runInteractiveCommand "telnet nyx.nyx.net" t <- hGetContentsTimeout h 15000 print t >> terminateProcess p
The input handle is being garbage collected and closed, so telnet is exiting. Try: main :: IO () main = do (hin, h, _, p) <- runInteractiveCommand "telnet nyx.nyx.net" t <- hGetContentsTimeout h 15000 print t hClose hin terminateProcess p Note that you can't do either the hClose or terminateProcess before you have forced the whole string (which print does here). You might prefer to pass hin and p to hGetContentsTimeout, and have it close/terminate them just before the return "".
hGetContentsTimeout :: Handle -> Int -> IO String hGetContentsTimeout h t = do hSetBuffering stdin NoBuffering ready <- hWaitForInput h t; eof <- hIsEOF h
You'll also need to remove the hIsEOF call from your code, or having decided that nothing is ready it will then block, waiting to see if there is an end of file or not. Thanks Ian
participants (3)
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Bulat Ziganshin -
Ian Lynagh -
Scott Bell