cmb21:

fo/haskell-cafe>, mailto:haskell-cafe-request@haskell.org?subject=subscribe Errors-To: haskell-cafe-bounces@haskell.org Status: O Content-Length: 778 Lines: 27

Hi,

I am observing some rather strange behaviour with writeFile.

Say I have the following code:

answer <- AbstractIO.readFile "filename" let (answer2, remainder) = parseAnswer answer if remainder == "" && answer2 == "" then do AbstractIO.putStrLn $ "completed" else do AbstractIO.putStrLn answer2 AbstractIO.writeFile "filename" remainder

With the above I get an error saying the resources to "filename" are locked. If I add the line "AbstractIO.putStrLn $ show (answer2, remainder) before I call writeFile it suddenly magically works!

lazy IO at play. One quick fix would be to use strict IO: import qualified Data.ByteString.Char8 as S import Data.ByteString (ByteString) main = do ans <- S.readFile "t" -- strict file IO print (S.length ans) -- current size let (x,xs) = S.splitAt 10 ans -- "parse" S.writeFile "t" xs ans' <- S.readFile "t" print (S.length ans') -- new size $ time ./a.out 2487212 2487202 This comes up often enough that I think we should have a strict readFile for Strings -- Don