How can I read keyboard without stopping

[Chip Salzenberg]

According to mouse at mcgill-vision.UUCP (der Mouse):
>3) FIONREAD.  BSD systems have an ioctl you can apply to a terminal
>   line to get the number of characters queued available for a read().
>   SV may have something similar; I don't know.
>
>   Bad:        - BSD only (as far as I know).

Xenix has the exact equivalent to FIONREAD, but it's not an ioctl() call.
Instead, it's a system call all its own: rdchk(fildes).  Return values are
-1 (not a tty fildes) or >= 0 (number of bytes available).
-- 
Chip Salzenberg                <chip at ateng.uu.net> or <uunet!ateng!chip>
A T Engineering                My employer may or may not agree with me.
        You make me wanna break the laws of time and space
                    You make me wanna eat pork