response_file.cpp

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// Copyright Vladimir Prus 2002-2004.
// 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)

/** This example shows how to handle response file.

    For a test, build and run:
       response_file -I foo @response_file.rsp

    The expected output is:
      Include paths: foo bar biz

    Thanks to Hartmut Kaiser who raised the issue of response files
    and discussed the possible approach.
*/


#include <boost/program_options/options_description.hpp>
#include <boost/program_options/parsers.hpp>
#include <boost/program_options/variables_map.hpp>
#include <boost/tokenizer.hpp>
#include <boost/token_functions.hpp>
using namespace boost;
using namespace boost::program_options;

#include <iostream>
#include <fstream>
using namespace std;

// Additional command line parser which interprets '@something' as a
// option "config-file" with the value "something"
pair<string, string> at_option_parser(string const&s)
{
    if ('@' == s[0])
        return std::make_pair(string("response-file"), s.substr(1));
    else
        return pair<string, string>();
}

int main(int ac, char* av[])
{
    try {
        options_description desc("Allowed options");
        desc.add_options()
            ("help", "produce a help message")
            ("include-path,I", value< vector<string> >()->composing(), 
                 "include path")
            ("magic", value<int>(), "magic value")
            ("response-file", value<string>(), 
                 "can be specified with '@name', too")
        ;

        variables_map vm;
        store(command_line_parser(ac, av).options(desc)
              .extra_parser(at_option_parser).run(), vm);

        if (vm.count("help")) {
            cout << desc;            
        }
        if (vm.count("response-file")) {
            // Load the file and tokenize it
            ifstream ifs(vm["response-file"].as<string>().c_str());
            if (!ifs) {
                cout << "Could not open the response file\n";
                return 1;
            }
            // Read the whole file into a string
            stringstream ss;
            ss << ifs.rdbuf();
            // Split the file content
            char_separator<char> sep(" \n\r");
            tokenizer<char_separator<char> > tok(ss.str(), sep);
            vector<string> args;
            copy(tok.begin(), tok.end(), back_inserter(args));
            // Parse the file and store the options
            store(command_line_parser(args).options(desc).run(), vm);            
        }

        if (vm.count("include-path")) {
            const vector<string>& s = vm["include-path"].as<vector< string> >();
            cout << "Include paths: ";
            copy(s.begin(), s.end(), ostream_iterator<string>(cout, " "));
            cout << "\n";
        }        
        if (vm.count("magic")) {
            cout << "Magic value: " << vm["magic"].as<int>() << "\n";
        }
    }
    catch(exception& e) {
        cout << e.what() << "\n";
    }
}