C ++ regular expressions with Boost Regex

Question

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

I have read a lot of regex documentation, but I just can't figure out how to do this.

I believe I can use this Perl expression to search for 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 still don't understand how to do the rest.

Answer 1

Perhaps you are looking for something like this. It uses regex_iterator to get all matches of the current template. See link .

 #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 that you have seen a reverse character match.

Answer 2

 #include <string> #include <list> #include <boost/regex.hpp> typedef std::string::const_iterator ConstIt; int main() { // input text, expected result, & proper address pattern const std::string sInput ( "192.168.0.1 10.0.0.255 abc 10.5.1.00" " 1.2.3.4a 168.72.0 0.0.0.0 5.4.3.2" ); const std::string asExpected[] = { "192.168.0.1", "10.0.0.255", "0.0.0.0", "5.4.3.2" }; boost::regex regexIPs ( "(^|[ \t])(" "(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])[.]" "(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])[.]" "(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])[.]" "(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])" ")($|[ \t])" ); // parse, check results, and return error count boost::smatch what; std::list<std::string> ns; ConstIt end = sInput.end(); for (ConstIt begin = sInput.begin(); boost::regex_search(begin, end, what, regexIPs); begin = what[0].second) { ns.push_back(std::string(what[2].first, what[2].second)); } // check results and return number of errors (zero) int iErrors = 0; int i = 0; for (std::string & s : ns) if (s != asExpected[i ++]) ++ iErrors; return iErrors; } 

Answer 3

The proposed solution is not bad, thanks for that. Although I found a small error in the template itself.

For example, something like 49.000.00.01 will be accepted as a valid IPv4 address, and from my understanding it should not be (it just happened to me during some dump processing).

I suggest improving patter in:

 "\\b(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)" "\\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)" "\\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)" "\\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]?|0)\\b"; 

This should only allow 0.0.0.0 as an all-zero-in, which I suppose will be correct and it will eliminate all .00. 0,000. and etc.