Untitled

#include <iostream>
#include <fstream>
#include <string>

std::string read_file(const std::string& filename)
{
    std::ifstream file(filename.c_str());
    std::string str = std::string(
        (std::istreambuf_iterator<char>(file.rdbuf())),
        std::istreambuf_iterator<char>());
    return str;
}

std::string inner_html(
    const std::string& html,
    const std::string& node)
{
    size_t i0 = html.find("<"+node+">");
    if(i0 == std::string::npos)
        return "";
    i0 += node.size() + 2;

    size_t i1 = html.find("</"+node+">", i0);
    if(i1 == std::string::npos)
        return "";

    return html.substr(i0, i1 - i0);
}

struct html_parser
{
    std::string html;

    html_parser(const std::string& html) : html(html) {}

    html_parser inner(const std::string& node)
    {
        return html_parser(inner_html(html, node));
    }

    friend std::ostream& operator<<(std::ostream& os, const html_parser& hp)
    {
        os << hp.html;
        return os;
    }
};

int main()
{
    //std::string html_str = read_file("test.html");
    std::string html_str = "<html><p><strong>Books</strong></p></html>";
    html_parser html(html_str);
    std::cout << html.inner("p").inner("strong") << "\n";

    return 0;
}