#includeIn the above example, if no positional argument is provided, the error message returned by errorText method will be displayed on the console. This code example likely utilizes the Qt library, as QCommandLineParser is a class within the Qt framework.#include int main(int argc, char *argv[]) { QCoreApplication app(argc, argv); QCommandLineParser parser; parser.addPositionalArgument("filename", "The input file"); parser.process(app); if (parser.isSet("help")) { parser.showHelp(); return 0; } if (parser.positionalArguments().isEmpty()) { qCritical() << parser.errorText(); return -1; } QString filename = parser.positionalArguments().at(0); // Do something with filename return 0; }