non-blocking read

[mark at elsie.UUCP]

If you have the Berkeley new tty driver you can do the following:

#include <sgtty.h>

foo()
{
int	nchars = 0;

for (;;) {
	..loop code..

	ioctl(0,FIONREAD,(struct sgttyb *) &nchars);
	if (nchars) {
		/* Something has been typed at the keyboard */
		..anything else..
		}
	}
}

The FIONREAD causes the number of chars waiting at the terminal to be placed
in nchars. NOTE: if you want to process single chars as they come into the 
terminal you must be in RAW or CBREAK mode.

This is not terribly portable (I try to protect such code with
"#ifdef berkeley"'s). I would be interested in knowing if there is a truly
portable way of doing this.

-- 
Mark J. Miller
NIH/NCI/DCE/LEC
UUCP:	decvax!harpo!seismo!rlgvax!cvl!elsie!mark
Phone:	(301) 496-5688