Re: [Haskell-beginners] Runtime error while feeding a binary to stdin

11 Jan 2017

      Theodore Lief Gannon  writes:

Hi Theodore,

Thanks, I didn't know about those functions.

Best regards,
Manuel.
...
Those System.IO functions *are* String-specific. Try the equivalents from
Data.ByteString:
http://hackage.haskell.org/package/bytestring-0.10.8.1/docs/Data-ByteString....
On Tue, Jan 10, 2017 at 2:46 PM, Manuel Vázquez Acosta 
wrote:
...
Hi all,
I'm quite new to Haskell.  While following the "Real World Haskell" and
doing some experimentation I came up with a anoying situation:
Trying to read data from stdin it seems that binary data is not
allowed.  A simple "copy" program:
-- file: copy.hs
   import System.IO
main = do
      input <- hGetContents stdin
      hPutStr input
Fails when I run it like:
$ ghc copy.hs
   $ ./copy < input > output
   copy: <stdin>: hGetContents: invalid argument (invalid byte sequence)
input contains binary data.  In fact of all the following programs only
the first works with binary data:
copy:: IO ()
  copy = do
    bracket (openBinaryFile "input" ReadMode) hClose $ \hi -> do
      bracket (openBinaryFile "ouput" WriteMode) hClose $ \ho -> do
        input <- hGetContents hi
        hPutStr ho input
copy2:: IO ()
  copy2 = do
    -- Doesn't work with binary files
    source <- readFile "input"
    writeFile "output" source
copy3:: IO ()
  copy3 = do
    -- Doesn't work with binary files either
    interact (map $ \x -> x)
copy4:: IO ()
  copy4 = do
    input <- hGetContents stdin
    hPutStr stdout input
But I lost any chance of piping and/or using '<', '>' in the shell.
Best regards,
Manuel.
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