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

[Manuel]

Theodore Lief Gannon <tanuki at gmail.com> 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.html#g:29
>
> On Tue, Jan 10, 2017 at 2:46 PM, Manuel Vázquez Acosta <mva.led at gmail.com>
> 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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