1#include <unistd.h>
 2#include <errno.h>
 3#include <sys/ioctl.h>
 4#include "syscall.h"
 5
 6int isatty(int fd)
 7{
 8	struct winsize wsz;
 9	unsigned long r = syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz);
10	if (r == 0) return 1;
11	if (errno != EBADF) errno = ENOTTY;
12	return 0;
13}