Validations are almost all automatic. The GetOpt_pp class will throw an exception if the exception() method was called with the appropriate flags (see previous section), or returned false when casted to bool if the format was invalid.

However, you may want to check that the user didn't specify additional options you did not look for. Those options may got parsed, but you never extracted them with a manipulator, so they are still within the GetOpt_pp instance.

Two ways to do this: with and without exceptions.

Checking Without exceptions

The options_remain() method comes into scene: after you extracted all the known options, you can call this method in order to see if there are other options you didn't expect. Example: ```

ops >> Option('i', myOption); // OK

if (ops.options_remain()) cerr << "Oops! Unexpected options. Refer to help" << endl; ```

Checking With exceptions

You can call the end_of_options() method to tell GetOpt_pp that you finished extracting all the options, so if there are still more options, then that's an error. This method calls the options_remain() method, and if it returns true, throws TooManyOptionsEx. Only applicable when eofbit was specified. Example: ops.exceptions_all(); try { ops >> Option('i', myOption); // OK ops.end_of_options(); // you say: I'm done! } catch(TooManyOptionsEx) { cerr << "You specified more options than those I understand\n"; } catch(GetOptEx) { cerr << "Invalid options. Try again\n"; } //

Next: Querying without Manipulators

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