implement Tee; include "sys.m";	sys: Sys; include "draw.m"; include "arg.m"; Tee: module{	init:	fn(nil: ref Draw->Context, nil: list of string);}; File: adt{	fd:	ref Sys->FD;	name:	string;}; usage(){	sys->fprint(sys->fildes(2), "Usage: tee [-a] [file ...]\n");	raise "fail:usage";} init(nil: ref Draw->Context, args: list of string){	sys = load Sys Sys->PATH;	arg := load Arg Arg->PATH;	if(arg == nil)		err(sys->sprint("can't load %s: %r", Arg->PATH)); 	append := 0;	arg->init(args);	while((c := arg->opt()) != 0)		case c {		'a' =>	append = 1;		* =>		usage();		}	names := arg->argv();	arg = nil; 	fd0 := sys->fildes(0);	if(fd0 == nil)		err("no standard input");	nf := 0;	files := array[len names + 1] of ref File;	for(; names != nil; names = tl names){		f := hd names;		fd: ref Sys->FD;		if(append){			fd = sys->open(f, Sys->OWRITE);			if(fd != nil)				sys->seek(fd, big 0, 2);			else				fd = sys->create(f, Sys->OWRITE, 8r666);		}else			fd = sys->create(f, Sys->OWRITE, 8r666 );		if(fd == nil)			err(sys->sprint("cannot open %s: %r", f));		files[nf++] = ref File(fd, f);	}	files[nf++] = ref File(sys->fildes(1), "standard output");	buf := array[Sys->ATOMICIO] of byte;	while((n := sys->read(fd0, buf, len buf)) > 0){		for(i := 0; i < nf; i++)			if(sys->write(files[i].fd, buf, n) != n)				err(sys->sprint("error writing %s: %r", files[i].name));	}	if(n < 0)		err(sys->sprint("read error: %r"));} err(s: string){	sys->fprint(sys->fildes(2), "tee: %s\n", s);	raise "fail:error";}