implement Ftest;## test file permissions or attributes# include "sys.m";	sys: Sys;include "draw.m"; stderr: ref Sys->FD; Ftest: module{	init:	fn(ctxt: ref Draw->Context, argv: list of string);}; Topr, Topw, Topx, Tope, Topf, Topd, Tops: con iota; init(nil: ref Draw->Context, argl: list of string){	if(argl == nil)		return; 	sys = load Sys Sys->PATH;	stderr = sys->fildes(2); 	if (tl argl == nil)		usage(); 	a := hd tl argl;	argl = tl tl argl;	ok := 0;	case a {	"-f" =>		ok = filck(nxtarg(argl), Topf);	"-d" =>		ok = filck(nxtarg(argl), Topd);	"-r" =>		ok = filck(nxtarg(argl), Topr);	"-w" =>		ok = filck(nxtarg(argl), Topw);	"-x" =>		ok = filck(nxtarg(argl), Topx);	"-e" =>		ok = filck(nxtarg(argl), Tope);	"-s" =>		ok = filck(nxtarg(argl), Tops);	"-t" =>		fd := 1;		if (argl != nil) {			if (!isint(hd argl)) {				sys->fprint(stderr, "ftest: bad argument to -t\n");				usage();			}			fd = int hd argl;		}		ok = isatty(fd);	* =>		sys->fprint(stderr, "test: unknown option %s\n", a);		usage();	}	if (!ok)		raise "fail:false";} nxtarg(argl: list of string): string{	if(argl == nil) {		sys->fprint(stderr, "test: argument expected\n");		usage();	}	return hd argl;} usage(){	sys->fprint(stderr, "usage: (ftest -fdrwxes file)|(ftest -t fdno)\n");	raise "fail:usage";} isint(s: string): int{	if(s == nil)		return 0;	for(i := 0; i < len s; i++)		if(s[i] < '0' || s[i] > '9')			return 0;	return 1;}  filck(fname: string, Top: int): int{	(ok, dir) := sys->stat(fname); 	if(ok >= 0) {		ok = 0;		case Top {		Topr =>	# readable			ok = permck(dir, 8r004);		Topw =>	# writable			ok = permck(dir, 8r002);		Topx =>	# executable			ok = permck(dir, 8r001);		Tope =>	# exists			ok = 1;		Topf =>	# is a regular file			ok = (dir.mode & Sys->DMDIR) == 0;		Topd =>	# is a directory			ok = (dir.mode & Sys->DMDIR) != 0;		Tops =>	# has length > 0			ok = dir.length > big 0;		}	} 	return ok > 0;} permck(dir: Sys->Dir, mask: int): int{	uid, gid: string;	fd := sys->open("/dev/user", Sys->OREAD);	if(fd != nil) {		buf := array [28] of byte;		n := sys->read(fd, buf, len buf);		if(n > 0)			uid = string buf[0:n];	}	# how do I find out what my group is?		ok := dir.mode & mask<<0;	if(!ok && dir.gid == gid)		ok = dir.mode & mask<<3;	if(!ok && dir.uid == uid)		ok = dir.mode & mask<<6; 	return ok > 0;} isatty(fd: int): int{	d1, d2: Sys->Dir; 	ok: int;	(ok, d1) = sys->fstat(sys->fildes(fd));	if(ok < 0)		return 0;	(ok, d2) = sys->stat("/dev/cons");	if(ok < 0)		return 0; 	return d1.dtype==d2.dtype && d1.dev==d2.dev && d1.qid.path==d2.qid.path;}