On Wed, Mar 31, 2010 at 12:24 PM, David Leimbach wrote:

On Wed, Mar 31, 2010 at 12:02 PM, Gregory Collins

...

wrote:

...

David Leimbach writes:

...

to block or perhaps timeout, depending on the environment, looking for "some String" on an input Handle, and it appears that iteratee works in a very fixed block size. While a fixed block size is ok, if I can put back unused bytes into the enumerator somehow (I may need to put a LOT back in some cases, but in the common case I will not need to put any back as most expect-like scripts typically catch the last few bytes of data sent before the peer is blocked waiting for a response...)

See IterGV from the iteratee lib:

http://hackage.haskell.org/packages/archive/iteratee/0.3.1/doc/html/Data-Ite...

The second argument to the "Done" constructor is for the portion of the input that you didn't use. If you use the Monad instance, the unused input is passed on (transparently) to the next iteratee in the chain.

...

If you use attoparsec-iteratee ( http://hackage.haskell.org/packages/archive/attoparsec-iteratee/0.1/doc/html... ), you could write "expect" as an attoparsec parser:

...

------------------------------------------------------------------------ {-# LANGUAGE OverloadedStrings #-}

import Control.Applicative import Control.Monad.Trans (lift) import Data.Attoparsec hiding (Done) import Data.Attoparsec.Iteratee import qualified Data.ByteString as S import Data.ByteString (ByteString) import Data.Iteratee import Data.Iteratee.IO.Fd import Data.Iteratee.WrappedByteString import Data.Word (Word8) import System.IO import System.Posix.IO

expect :: (Monad m) => ByteString -> IterateeG WrappedByteString Word8 m () expect s = parserToIteratee (p >> return ()) where p = string s <|> (anyWord8 >> p)

dialog :: (Monad m) => IterateeG WrappedByteString Word8 m a -- ^ output end -> IterateeG WrappedByteString Word8 m () dialog outIter = do expect "login:" respond "foo\n" expect "password:" respond "bar\n" return ()

where respond s = do _ <- lift $ enumPure1Chunk (WrapBS s) outIter >>= run return ()

main :: IO () main = do hSetBuffering stdin NoBuffering hSetBuffering stdout NoBuffering enumFd stdInput (dialog output) >>= run where output = IterateeG $ \chunk -> case chunk of (EOF _) -> return $ Done () chunk (Chunk (WrapBS s)) -> S.putStr s >> hFlush stdout >> return (Cont output Nothing) ------------------------------------------------------------------------

Usage example:

$ awk 'BEGIN { print "login:"; fflush(); system("sleep 2"); \ print "password:"; fflush(); }' | runhaskell Expect.hs foo bar

N.B. for some reason "enumHandle" doesn't work here w.r.t buffering, had to go to POSIX i/o to get the proper buffering behaviour.

That's pretty neat actually. I'm going to have to incorporate timeouts into something like that (and attoparsec-iteratee doesn't install for me for some reason, I'll try again today).

worked fine today...

That leads me to another question in another thread I'm about to start.

And that other thread is not going to happen, because I realized I was just having issues with non-strict vs strict evaluation :-) It makes perfect sense now... gist is: timeout (10 ^ 6) $ return $ sum [1..] and timeout (10 ^ 6) $! return $ sum [1..] will not timeout, and will hang while timeout (10 ^ 6) $ return $! sum [1..] does timeout... and everything in the Haskell universe is nice and consistent. Dave

Dave

...

G -- Gregory Collins