code: public static void main(String[] argv) throws IOException {
      int ret;
      InstancedConfiguration conf = new InstancedConfiguration(ConfigurationUtils.defaults());
  
      if (!ConfigurationUtils.masterHostConfigured(conf) && argv.length > 0) {
        System.out.println(ConfigurationUtils
            .getMasterHostNotConfiguredMessage("Alluxio job shell"));
        System.exit(1);
      }
  
      try (JobShell shell = new JobShell(conf)) {
        ret = shell.run(argv);
      }
      System.exit(ret);
    }
docs: Main method, starts a new JobShell.
  
  @param argv array of arguments given by the user's input from the terminal