[Boost-users] [Regex] : Unknown character sequence.

Hi, I'm new to regex. This is basically what I was trying. #include <iostream> #include int main() { std::string input = "sand._12"; boost::regex reg(".*\._[0-9]+"); ...... } I get a warning which says "Unknown escape sequence '\.' . Its the same case with any other special character or even '\s' . I guess I'm missing something very simple. Any ideas ? Thanks in advance. -- -Sandeep.