On 09 June 2005 02:47, Lei Pan wrote:
Could anyone tell me how to open a block device (e.g., /dev/hda1) into a IO Handle by using GHC (version > 5.0)? I want to open a block/char device and return a handle. Apparently, openFile function can't do the job. It will be very appreciated if someone could give me a hint.
An earlier post pointed out the problem, but got no reply.
http://www.haskell.org/pipermail/glasgow-haskell-users/2001-November/002 624.html
Something I played in GHCI-6.2.2
*Main> openFile "/dev/hdb2" ReadMode >>= \hin -> hGetPosn hin >>= \pos -> print pos
*** Exception: /dev/hdb2: openFile: unsupported operation (unknown file type)
(I already set /dev/hdb2 globally read/write)
I'll look into fixing this. In the meantime, you should be able to use the System.Posix library to open the file directly, and then convert the FD to a Handle using GHC.Handle.openFd (I don't think fdToHandle will work in this case, because it checks the file type). Bear in mind that GHC.Handle.openFd is an internal undocumented interface, so may change in the future. Cheers, Simon