implement Dbmkeys; include "sys.m";	sys: Sys; include "draw.m"; include "dbm.m";	dbm: Dbm;	Datum, Dbf: import dbm; Dbmkeys: module{	init: fn(nil: ref Draw->Context, args: list of string);}; init(nil: ref Draw->Context, args: list of string){	sys = load Sys Sys->PATH;	dbm = load Dbm Dbm->PATH; 	dbm->init(); 	args = tl args;	db := Dbf.open(hd args, Sys->OREAD);	if(db == nil){		sys->fprint(sys->fildes(2), "dbm/keys: %s: %r\n", hd args);		raise "fail:open";	}	for(key := db.firstkey(); key != nil; key = db.nextkey(key))		sys->print("%s\n", string key);}