implement Mv; include "sys.m";	sys: Sys;	stderr: ref Sys->FD; include "draw.m";	draw: Draw; include "string.m";	str: String;  Mv: module {	init: fn(ctxt: ref Draw->Context, argv: list of string);}; init(nil: ref Draw->Context, argv: list of string){	sys = load Sys Sys->PATH;	stderr = sys->fildes(2);	str = load String String->PATH;	if(str == nil) {		sys->fprint(stderr, "mv: can't load %s: %r\n", String->PATH);		raise "fail:load";	} 	dirto, dirfrom: Sys->Dir;	todir, toelem: string;	if(len argv<3) {		sys->fprint(stderr, "usage: mv fromfile tofile\n");		sys->fprint(stderr, "       mv fromfile ... todir\n");		raise "fail:usage";	}	argv = tl argv;	arr := array[len argv] of string;	for (i:=0; argv!=nil;i++){		arr[i]= hd argv;		argv = tl argv;	}	(i,dirto)=sys->stat(arr[len arr-1]);	if(i >= 0 && (dirto.mode&Sys->DMDIR)){		(i,dirfrom)=sys->stat(arr[0]);		if(len arr == 2 && i >= 0 && (dirfrom.mode&Sys->DMDIR))			(todir,toelem)=split(arr[len arr-1]);		else{			todir = arr[len arr -1];			toelem = "";	# toelem will be fromelem 		}	}else		(todir,toelem)=split(arr[len arr-1]);	if(len arr > 2  && toelem != nil) {		sys->fprint(stderr, "mv: %s not a directory\n", arr[len arr-1]);		raise "fail:error";	}	failed := 0;	for(i=0; i < len arr-1; i++)		if (mv(arr[i], todir, toelem) < 0)			failed++;	if(failed)		raise "fail:error";} mv(from,todir,toelem : string): int{	(i,dirb):=sys->stat(from);	if(i != 0) {		sys->fprint(stderr, "mv: can't stat %s: %r\n", from);		return -1;	}	(fromdir,fromelem):=split(from);	fromname:= fromdir+fromelem;	if(toelem == nil){		if (todir[len todir-1]!='/')			todir[len todir]='/';		toelem = fromelem;	}	i = len toelem;	if(i==0){		sys->fprint(stderr, "mv: null last name element moving %s\n", fromname);		return -1;	}	toname:=todir+toelem;	if(samefile(fromdir, todir)){		if(samefile(fromname, toname)){			sys->fprint(stderr, "mv: %s and %s are the same\n", fromname, toname);			return -1;		}		(j,dirt):=sys->stat(toname);		if( (j == 0) && (dirb.mode&Sys->DMDIR) ){			sys->fprint(stderr, "mv: can't rename a directory to an existing name\n");			return -1;		}		if(j == 0)			hardremove(toname);		dirt = sys->nulldir;		dirt.name=toelem;		if(sys->wstat(fromname,dirt) >= 0)			return 0;		if(dirb.mode&Sys->DMDIR){			sys->fprint(stderr, "mv: can't rename directory %s: %r\n", fromname);			return -1;		}	}	# Renaming won't work --- have to copy	if(dirb.mode&Sys->DMDIR){		sys->fprint(stderr, "mv: %s is a directory, not copied to %s\n", fromname, toname);		return -1;	}	fdf := sys->open(fromname, Sys->OREAD);	if(fdf==nil){		sys->fprint(stderr, "mv: can't open %s: %r\n", fromname);		return -1;	}	fdt := sys->create(toname, Sys->OWRITE, dirb.mode);	if(fdt == nil){		sys->fprint(stderr, "mv: can't create %s: %r\n", toname);		return -1;	}	if ((stat := copy1(fdf, fdt, fromname, toname)) != -1)		fdf = nil;	# temp bug: sometimes can't remove open file		if (sys->remove(fromname) < 0) {			sys->fprint(stderr, "mv: can't remove %s: %r\n", fromname);			return -1;		}	return stat;}  copy1(fdf, fdt : ref Sys->FD,from, fto : string): int{	n : int;	buf:=array[Sys->ATOMICIO] of byte;	for(;;) {		n = sys->read(fdf, buf, len buf);		if (n<=0)			break;		n1 := sys->write(fdt, buf, n);		if(n1 != n) {			sys->fprint(stderr, "mv: error writing %s: %r\n", fto);			return -1;		}	}	if(n < 0) {		sys->fprint(stderr, "mv: error reading %s: %r\n", from);		return -1;	}	return 0;} split(name : string): (string,string){	(d,t) := str->splitr(name, "/");	if(d!=nil)		return(d,t);	else if(name=="..")		return("../",".");	else		return("./",name);} samefile(a,b : string): int{	if(a==b) 		return 1;	(i,da):=sys->stat(a);	(j,db):=sys->stat(b);	if(i < 0 || j < 0)		return 0;	i= (da.qid.path==db.qid.path && da.qid.vers==db.qid.vers &&		da.dev==db.dev && da.dtype==db.dtype);	return i;} hardremove(a: string){	if(sys->remove(a) == -1){		sys->fprint(stderr, "mv: can't remove %s: %r\n", a);		raise "fail:mv";	}	do; while(sys->remove(a) != -1);}