#include <iostream>
#include <vector>
#include <regex>
 
int main() {
	const std::string s = "4345t435\ng54t a_file_123.xml rk\ngreg a_file_j34.xml fger 43t54";
	const std::regex rx("a_file_\\w+\\.xml");
	std::vector<std::string> results(std::sregex_token_iterator(s.begin(), s.end(), rx),
                               std::sregex_token_iterator());
 
	std::cout << "Number of matches: " << results.size() << std::endl;
	for (auto result : results)
	{
		std::cout << result << std::endl;
	}
	return 0;
}

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