________________________________ From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Sandeep Bantia Sent: Tuesday, February 07, 2006 7:23 PM To: boost-users@lists.boost.org Subject: [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]+"); If you're trying to escape the "." you probably also need to escape the "\" by using "\\". It is a C string after all.