void run(String [] args){
        
        CmdOptionTester optionTester = new CmdOptionTester();
        CmdOptions parser = new CmdOptions();
        
        Option odir = parser.addStringOption('d', "dir");
        
        try {
            parser.parse(args);
            } catch (IllegalOptionValueException ex) {
            Logger.getLogger(ReplaceGTChars.class.getName()).log(Level.SEVERE, null, ex);
        } catch (UnknownOptionException ex) {
            Logger.getLogger(ReplaceGTChars.class.getName()).log(Level.SEVERE, null, ex);
        }
        
        String d = optionTester.testDirectory(parser, odir);
        
        if (d != null) {
                File dir = new File(d);
                FileListFilter select = new FileListFilter("", "out.txt");
                File[] files = dir.listFiles(select);
                
                for (File fi : files) {
                    // we need to parse the txt
                    // change 3spaces by a tab
                    
                }
        }
    }