1 files changed, 47 insertions, 0 deletions
diff --git a/src/boost/libs/program_options/example/env_options.cpp b/src/boost/libs/program_options/example/env_options.cpp
new file mode 100644
index 00000000..bab37e25
--- /dev/null
+++ b/src/boost/libs/program_options/example/env_options.cpp
@@ -0,0 +1,47 @@
+// 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;
+}