[Haskell-cafe] After `readFile`, why cannot i `writeFile` ?

[Bill Atkins]

readFile reads the file lazily so it isn't closed until the entire contents have been consumed.

Try System.IO.Strict.readFile, which will read the entire file at once.

zaxis <z_axis at 163.com> writes:

> hitSSQ :: String -> [Int] -> IO ()
> hitSSQ no hitNum = do
>    let newNum = unwords $ [no] ++ map (\n -> show n) hitNum
>    hitNums <- fmap lines $ readFile "test.txt"
>    writeFile "test.txt" $ unlines $ hitNums ++ [newNum]
> 
> *** Exception: test.txt: openFile: resource busy (file is locked)