code: public boolean execute(String commandLine) {
          try {
              doExecute(commandLine);
              return true;
          } catch (ParseException e) {
              handleParseException(e);
          } catch (Exception e) {
              err.printThrowable(e);
          }
          return false;
      }
docs: Execute the command line.
  The command line will be parsed, verified for correctness and executed if it passes all correctness checks.
  Any output is printed as a side effect to the {@link CliOutput} this shell was constructed with.
  If any error occurs while parsing the command line or executing the parsed command line, it will also be printed
  to the {@link CliOutput} this shell was constructed with.
  
  @param commandLine Command line to execute.
  @return {@code true} if the command line was executed successfully.