Bug or not bug? Files.newInputStream() on a Path which is a directory does not fail until you read from it

[Alan Bateman]

On 05/12/2014 22:44, Francis Galiegue wrote:
> Witness this main():
>
> public static void main(final String... args)
>      throws IOException
> {
>      final Path path = Paths.get("/home/fge/tmp/XXX");
>      try (
>          final InputStream in = Files.newInputStream(path);
>      ) {
>          final byte[] buf = new byte[1024];
>          int bytesRead;
>          while ((bytesRead = in.read(buf)) != -1)
>              System.out.printf("%d bytes read\n", bytesRead);
>      }
> }
>
> On my system, "/home/fge/tmp/XXX" is a directory. I'd have expected
> that it failed when I tried and opened the stream on it, except that
> the stacktrace I got is:
>
> Exception in thread "main" java.io.IOException: Is a directory
> at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
>
It's not prohibited by the spec because directories can be opened as 
regular files on some platforms. So what you are seeing it just platform 
specific behavio.

This is clearly not obvious behavior so we should looking at using fstat 
after opening a file for read access to avoid the confusion (at least on 
platforms where we can open a directory for reading but where reading is 
not actually allowed). I will create a bug for this.

-Alan.