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- // Copyright Thomas Kent 2016
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE_1_0.txt
- // or copy at http://www.boost.org/LICENSE_1_0.txt)
- #include <boost/program_options.hpp>
- namespace po = boost::program_options;
- #include <string>
- #include <iostream>
- std::string mapper(std::string env_var)
- {
- // ensure the env_var is all caps
- std::transform(env_var.begin(), env_var.end(), env_var.begin(), ::toupper);
- if (env_var == "PATH") return "path";
- if (env_var == "EXAMPLE_VERBOSE") return "verbosity";
- return "";
- }
- void get_env_options()
- {
- po::options_description config("Configuration");
- config.add_options()
- ("path", "the execution path")
- ("verbosity", po::value<std::string>()->default_value("INFO"), "set verbosity: DEBUG, INFO, WARN, ERROR, FATAL")
- ;
- po::variables_map vm;
- store(po::parse_environment(config, boost::function1<std::string, std::string>(mapper)), vm);
- notify(vm);
- if (vm.count("path"))
- {
- std::cout << "First 75 chars of the system path: \n";
- std::cout << vm["path"].as<std::string>().substr(0, 75) << std::endl;
- }
- std::cout << "Verbosity: " << vm["verbosity"].as<std::string>() << std::endl;
- }
- int main(int ac, char* av[])
- {
- get_env_options();
- return 0;
- }
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