3 points
Rob carried the standard well for the “spirit of UNIX,”
if (isatty(1)) {
if (ioctl(1,JMUX,0) >= 0) {
struct winsize win;
if (ioctl(1,JWINSIZE,&win) >= 0) {
screenwidth = win.bytesx;
if (screenwidth == 0)
screenwidth++;
}
}
qflg = Cflg = 1;
(void) gtty(1, &sgbuf);
if ((sgbuf.sg_flags & XTABS) == 0)
usetabs = 1;
}