[9fans] isatty

[Boyd Roberts <boyd@strakt.com>]

Given I had to implement this 'thing' on Plan 9 I decided on:

#include <u.h>
#include <libc.h>

static char *cons = "/dev/cons";

/*
 * Compare fd to cons should get it right.
 */
int
isatty(int fd)
{
	Dir c;
	Dir f;

	if (dirstat(cons, &c) != 0)
		return 0;

	if (dirfstat(fd, &f) != 0)
		return 0;

	return f.type == c.type &&
		f.dev == c.dev &&
		f.qid.path == c.qid.path &&
		f.qid.vers == c.qid.vers;
}

Seemed obvious to me, but is this a good plan?

The overkill on the multiple dirstat's on /dev/cons and
qid comparison I thought would ensure that I wouldn't
get fooled [again].