anchor.diff:    var maxCount = int.parse(params[OPTION_MAX_USERS], onError: (s) => 0);
     var users = await getGplusUsers(communityFile, apiKey, maxCount);
   
  -  var output = stdout;
  -  if (params.options.contains(OPTION_OUTPUT_FILE)) {
  -    output = new File(params[OPTION_OUTPUT_FILE]).openWrite();
  +  var seen = new Set<String>();
  +  var duplicates = new List<String>();
  +  users.forEach((user) {
  +    var name = user.displayName;
  +    if (seen.contains(name)) {
  +      duplicates.add(name);
  +    } else {
  +      print(user);
  +      seen.add(name);
  +    }
  +  });
  +  print('${users.length} total members.');
  +  if (duplicates.isNotEmpty) {
  +    print('!!! ${duplicates.length} duplicate(s) !!!');
  +    duplicates.forEach((name) => print(' - ${name}'));
     }
  -  users.forEach((user) {
  -    output.writeln(user);
  -  });
  -  output.writeln('${users.length} members.');
  -  output.close();
   }
  
positive.code:       ..addOption(OPTION_COMMUNITY_PAGE, abbr: 'c')
        ..addOption(OPTION_API_KEY, abbr: 'a')
        ..addOption(OPTION_MAX_USERS, abbr: 'm', defaultsTo: '0')
        ..addOption(OPTION_OUTPUT_FILE, abbr: 'o')
        ..addFlag(FLAG_HELP, negatable: false, abbr: 'h');
    var params = parser.parse(args);
    if (params[FLAG_HELP] ||
  
negative.code: const OPTION_COMMUNITY_PAGE = 'community_page';
  const OPTION_API_KEY = 'api_key';
  const OPTION_MAX_USERS = 'max_users';
  const FLAG_HELP = 'help';
  
  main(List<String> args) async {
  