leaveye.guo:
To read the handle openBinaryFile returns, both the hGetBuf and hGetBufNonBlocking needs one parameter _buf_ of type Ptr a. I can not get one data of that type.
In the doc, there is only nullPtr, and also some type cast functions. I failed to find some other buffer-maker function.
What should I do ?
I mean, what problem are you trying to solve? Ptrs aren't the usual way to manipulate files in Haskell. Here, for example, is a small program to print the first byte of a binary file: import System.IO import qualified Data.ByteString as B main = do h <- openBinaryFile "a.out" ReadMode s <- B.hGetContents h print (B.head s) When run: $ ./a.out 127 Note there's no mallocs or pointers involved. -- Don