1 // Copyright Thomas Kent 2016
2 // Distributed under the Boost Software License, Version 1.0.
3 // (See accompanying file LICENSE_1_0.txt
4 // or copy at http://www.boost.org/LICENSE_1_0.txt)
5
6 #include <boost/program_options.hpp>
7 namespace po = boost::program_options;
8 #include <string>
9 #include <iostream>
10
mapper(std::string env_var)11 std::string mapper(std::string env_var)
12 {
13 // ensure the env_var is all caps
14 std::transform(env_var.begin(), env_var.end(), env_var.begin(), ::toupper);
15
16 if (env_var == "PATH") return "path";
17 if (env_var == "EXAMPLE_VERBOSE") return "verbosity";
18 return "";
19 }
20
get_env_options()21 void get_env_options()
22 {
23 po::options_description config("Configuration");
24 config.add_options()
25 ("path", "the execution path")
26 ("verbosity", po::value<std::string>()->default_value("INFO"), "set verbosity: DEBUG, INFO, WARN, ERROR, FATAL")
27 ;
28
29 po::variables_map vm;
30 store(po::parse_environment(config, boost::function1<std::string, std::string>(mapper)), vm);
31 notify(vm);
32
33 if (vm.count("path"))
34 {
35 std::cout << "First 75 chars of the system path: \n";
36 std::cout << vm["path"].as<std::string>().substr(0, 75) << std::endl;
37 }
38
39 std::cout << "Verbosity: " << vm["verbosity"].as<std::string>() << std::endl;
40 }
41
main(int ac,char * av[])42 int main(int ac, char* av[])
43 {
44 get_env_options();
45
46 return 0;
47 }
48