#include <unistd.h>
+#include <errno.h>
#include <sys/ioctl.h>
#include "syscall.h"
int isatty(int fd)
{
struct winsize wsz;
- return !__syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz);
+ unsigned long r = syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz);
+ if (r == 0) return 1;
+ if (errno != EBADF) errno = ENOTTY;
+ return 0;
}