Question

I am trying to take a string in C++ and find all IP addresses contained inside, and put them into a new vector string.

I’ve read a lot of documentation on regex, but I just can’t seem to understand how to do this simple function.

I believe I can use this Perl expression to find any IP address:

re("\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b");

But I am still stumped on how to do the rest.

Answer 1

Perhaps you’re looking for something like this. It uses regex_iterator to get all matches of the current pattern. See reference.

#include <boost/regex.hpp>
#include <iostream>
#include <string>

int main()
{
    std::string text(" 192.168.0.1 abc 10.0.0.255 10.5.1 1.2.3.4a 5.4.3.2 ");
    const char* pattern =
        "\\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)"
        "\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)"
        "\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)"
        "\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b";
    boost::regex ip_regex(pattern);

    boost::sregex_iterator it(text.begin(), text.end(), ip_regex);
    boost::sregex_iterator end;
    for (; it != end; ++it) {
        std::cout << it->str() << "\n";
        // v.push_back(it->str()); or something similar     
    }
}

Output:

192.168.0.1
10.0.0.255
5.4.3.2

Side note: you probably meant \\b instead of \b; I doubt you watnted to match backspace character.