At line 206 of this file there is a withFd function that might suit your needs, https://patch-tag.com/r/mae/sendfile/snapshot/current/content/pretty/src/Net... -- The Fd should not be used after the action returns because the -- Handler may be garbage collected and than will cause the finalizer -- to close the fd. withFd :: Handle -> (Fd -> IO a) -> IO a #ifdef __GLASGOW_HASKELL__ #if __GLASGOW_HASKELL__ >= 611 withFd h f = withHandle_ "withFd" h $ \ Handle__{..} -> do case cast haDevice of Nothing -> ioError (ioeSetErrorString (mkIOError IllegalOperation "withFd" (Just h) Nothing) "handle is not a file descriptor") Just fd -> f (Fd (fromIntegral (FD.fdFD fd))) #else withFd h f = withHandle_ "withFd" h $ \ h_ -> f (Fd (fromIntegral (haFD h_))) #endif #endif It uses GHC internals stuff, so it could easily break someday. On Thu, Jan 27, 2011 at 2:00 PM, Volker Wysk wrote:

Hello

I need to get the file descriptor, which is encapsulated inside a handle. handleToFd gets it, but the fd is closed. Is it possible to extract the fd from the handle, without modifying the handle?

Greetings, Volker

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