implement Cd; include "sys.m";	sys: Sys; include "draw.m"; Cd: module{	init:	fn(ctxt: ref Draw->Context, argv: list of string);}; stderr: ref Sys->FD; init(nil: ref Draw->Context, argv: list of string){	sys = load Sys Sys->PATH; 	stderr = sys->fildes(2); 	argv = tl argv;	if(argv == nil)		argv = "/usr/"+user() :: nil; 	if(tl argv != nil) {		sys->fprint(stderr, "Usage: cd [directory]\n");		raise "fail:usage";	} 	if(sys->chdir(hd argv) < 0) {		sys->fprint(stderr, "cd: %s: %r\n", hd argv);		raise "fail:failed";	}} user(): string{	fd := sys->open("/dev/user", sys->OREAD);	if(fd == nil)		return "inferno"; 	buf := array[Sys->NAMEMAX] of byte;	n := sys->read(fd, buf, len buf);	if(n <= 0)		return "inferno"; 	return string buf[0:n];}