How can I use Boost.Program_options to find the line number of a specific entry in an INI file?

Cross-platform way to get line number of an INI file where given option was found

Many applications today use .ini files to store configuration data. These files are simple and easy to parse. However, finding the line number of a specific entry can be difficult without the help of a library.

Boost.Program_options is a C library that provides a convenient way to parse and store command-line options. It also has support for parsing .ini configuration files.

To use Boost.Program_options to find the line number of an .ini entry, you can use the following steps:

1. Create a boost::program_options::options_description object to describe the options in your .ini file.
2. Create a boost::program_options::variables_map object to store the values of the options.
3. Use the boost::program_options::store() function to parse the .ini file and store the values in the variables_map object.
4. Use the boost::program_options::notify() function to validate the values in the variables_map object.

If any of the values in the variables_map object are invalid, the notify() function will throw an exception. This exception will contain the line number of the invalid value.

Here is an example of how to use Boost.Program_options to find the line number of an .ini entry:

<code class="cpp">#include <boost/program_options.hpp>
#include <iostream>

int main(int argc, char** argv) {
  try {
    // Create an options description object.
    boost::program_options::options_description options;
    options.add_options()
      ("my-option", boost::program_options::value<std::string>(), "My option");

    // Create a variables map object.
    boost::program_options::variables_map vm;

    // Parse the INI file.
    boost::program_options::store(boost::program_options::parse_config_file<char>("my.ini", options), vm);

    // Validate the values.
    boost::program_options::notify(vm);

    // Find the line number of the "my-option" option.
    if (vm.count("my-option")) {
      std::cout << "The line number of the \"my-option\" option is: " << vm["my-option"].source() << std::endl;
    } else {
      std::cout << "The \"my-option\" option was not found." << std::endl;
    }
  } catch (std::exception& e) {
    std::cerr << "Error: " << e.what() << std::endl;
    return 1;
  }

  return 0;
}</code>

This code will parse the my.ini file and store the values in the variables_map object. It will then validate the values and find the line number of the "my-option" option. If the option is not found, the code will print an error message.

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