Support for the TIOCINQ ioctl

Andy Koppe
Sat Aug 28 14:14:00 GMT 2010

On 27 August 2010 23:31, Brennan Peter Sellner wrote:
> By any chance, has support for the TIOCINQ ioctl on file descriptors (used
> to check how many bytes of data are in the input buffer) been added to
> Cygwin?  It hadn't as of 2004:

It's still implemented only for serial devices.

> ...but I haven't found any newer references to it.  I'm inferring that it's
> not supported, as ioctl(fd, TIOCINQ, &available) (where fd is a valid file
> descriptor, and available is a long) fails, with errno set to 'invalid
> argument'.  I'm running Cygwin 1.7.6 on Vista.
> I'm hoping I'm missing something...  Is there an alternative way to check
> the number of bytes on an fd's input buffer in Cygwin?

What's your use case? And on what sort of fd?

select() of course can tell you whether there are any bytes available
to be read from an fd, and usually that's all one needs to know.


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