How do you validate that a string is a valid IPv4 address in C++?

Question

I don\'t need to validate that the IP address is reachable or anything like that. I just want to validate that the string is in dotted-quad (xxx.xxx.xxx.xxx) IPv4 format, w

Answer 1

void validate_ip_address(const std::string& s) {
    const std::string number_0_255 = "((([0-9])|([1-9][0-9])|(1[0-9][0-9]|2[0-4][0-9]|25[0-5])){1})";
    const std::string dot = "(\\.){1}";
    static const boost::regex e(number_0_255 + dot + number_0_255 + dot + number_0_255 + dot + number_0_255);
    if (!regex_match(s, e)) {
        throw std::runtime_error(std::string("Uncorrect address IP: ") + s);
    }
}