Question

我想在程序中实现类似命令行的界面。所以我收到遵循正常命令行语法的字符串（例如“-G foo -dp bar --help”）。由于我不想再次实现解析器，我想使用Boost。

问题是：如何将字符串传递给Boost程序选项而不是argCount和argValues的组合。我是否需要先将文本转换为数字（argCount）和char *数组（argValues）才能完成？如果是的话......有一种简单的方法吗？

提前致谢。

Answer 1

一种方法是将std::string标记为std::vector<std::string>，然后将结果传递给Boost.ProgramOption的command_line_parser。 Boost.ProgramOption的documentation简要介绍了这种方法。另外，我在this回答的一部分中使用了类似的方法。

这是一个最小的完整示例：

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

#include <boost/bind.hpp>
#include <boost/program_options.hpp>
#include <boost/tokenizer.hpp>

// copy_if was left out of the C++03 standard, so mimic the C++11
// behavior to support all predicate types.  The alternative is to
// use remove_copy_if, but it only works for adaptable functors.
template <typename InputIterator,
          typename OutputIterator, 
          typename Predicate>
OutputIterator 
copy_if(InputIterator first,
        InputIterator last,
        OutputIterator result,
        Predicate pred)
{
  while(first != last)
  {
    if(pred(*first))
      *result++ = *first;
    ++first;
  }
  return result;
}

/// @brief Tokenize a string.  The tokens will be separated by each non-quoted
///        space or equal character.  Empty tokens are removed.
///
/// @param input The string to tokenize.
///
/// @return Vector of tokens.
std::vector<std::string> tokenize(const std::string& input)
{
  typedef boost::escaped_list_separator<char> separator_type;
  separator_type separator("\\",    // The escape characters.
                           "= ",    // The separator characters.
                           "\"\'"); // The quote characters.

  // Tokenize the intput.
  boost::tokenizer<separator_type> tokens(input, separator);

  // Copy non-empty tokens from the tokenizer into the result.
  std::vector<std::string> result;
  copy_if(tokens.begin(), tokens.end(), std::back_inserter(result), 
          !boost::bind(&std::string::empty, _1));
  return result;
}

int main()
{
  // Variables that will store parsed values.
  std::string address;
  unsigned int port;      

  // Setup options.
  namespace po = boost::program_options;
  po::options_description desc("Options");
  desc.add_options()
    ("address", po::value<std::string>(&address))
    ("port",    po::value<unsigned int>(&port))
    ;

  // Mock up input.
  std::string input = "--address 127.0.0.1 --port 12345";

  // Parse mocked up input.
  po::variables_map vm;
  po::store(po::command_line_parser(tokenize(input))
                .options(desc).run(), vm);
  po::notify(vm);

  // Output.
  std::cout << "address = " << address << "\n"
               "port = " << port << std::endl;
}

产生以下输出：

address = 127.0.0.1
port = 12345

Answer 2

正如@FaceBro 指出的那样，

boost::program_options 有一个名为 split_unix 的函数。它也适用于 Windows，因此以下是跨平台的，借用了已接受答案的主要示例结构：

int main()
{
  // Variables that will store parsed values.
  std::string address;
  unsigned int port;      

  // Setup options.
  namespace po = boost::program_options;
  po::options_description desc("Options");
  desc.add_options()
    ("address", po::value<std::string>(&address))
    ("port",    po::value<unsigned int>(&port))
    ;

  // Mock up input.
  std::string input = "--address 127.0.0.1 --port 12345";

  // Parse mocked up input.
  po::variables_map vm;
  po::store(po::command_line_parser(po::split_unix(input))
                .options(desc).run(), vm);
  po::notify(vm);

  // Output.
  std::cout << "address = " << address << "\n"
               "port = " << port << std::endl;
}

使用Boost Program Options来解析任意字符串

2 个答案: