print usage

src/cxxopts.cpp

@@ -396,7 +396,8 @@ Options::help() const
 
   size_t longest = 0;
 
-  std::string result;
+  std::string result = "Usage:\n  " + m_program + " [OPTION...] " 
+    + m_help_string + "\n\n";
 
   for (const auto& o : group->second)
   {

src/cxxopts.hpp

@@ -329,6 +329,12 @@ namespace cxxopts
   {
     public:
 
+    Options(std::string program, std::string help_string = "")
+    : m_program(std::move(program))
+    , m_help_string(std::move(help_string))
+    {
+    }
+
     void
     parse(int& argc, char**& argv);
 
@@ -410,6 +416,9 @@ namespace cxxopts
       const std::string& name
     );
 
+    std::string m_program;
+    std::string m_help_string;
+
     std::map<std::string, std::shared_ptr<OptionDetails>> m_options;
     std::string m_positional;
 

src/example.cpp

@@ -31,7 +31,7 @@ int main(int argc, char* argv[])
   try
   {
 
-    cxxopts::Options options;
+    cxxopts::Options options(argv[0]);
 
     options.add_options()
       ("a,apple", "an apple")