Small problem with match_results. Hope somone can help. On file1.txt, I match ten times. That is correct. On file2.txt, I match 5 times... as you can see, that is incorrect. For some reason, I only match the first column. Source code is at the bottom. Any ideas? Thanks... Brad content of file1.txt: 1111 2222 3333 4444 5555 6666 7777 8888 9999 0000 content of file2.txt: 1111 2222 3333 4444 5555 6666 7777 8888 9999 0000 c++ Boost Regex Source: int main() { long long total = 0; std::string line; boost::regex re( "\\b\\d{4}\\b" ); boost::smatch matches; while (std::cin) { std::getline(std::cin, line); if (boost::regex_search(line, matches, re)) { std::cout << matches << std::endl; ++total; } } std::cout << total << " matches" << std::endl; return 0; }