Hi, Environment: Windows 7 (32 bit), Visual Studio 2010 (Visual C++) I am trying to use Boost REGEX regex_match algorithm. I am using its grep flag. My code is as follows and here (a)* matches string "aaa", but still b comes out to be false. 1 2 3 4 5 6 7 8 9 10 11 bool MatchWithGrep(string& pattern, string& data) { const boost::regex e(pattern.c_str(), boost::regex::grep); return regex_match(data.c_str(), e); } I am passing following parameters bool b = MatchWithGrep("(a)*\\n123", "aaa"); In Boost Help, following is documented. Link - http://www.boost.org/doc/libs/1_55_0/libs/regex/doc/html/boost_regex/syntax/ basic_syntax.html When an expression is compiled with the flag grep set, then the expression is treated as a newline separated list of POSIX-Basic expressions, a match is found if any of the expressions in the list match, for example: boost::regex e("abc\ndef", boost::regex::grep); will match either of the POSIX-Basic expressions "abc" or "def". Considering this, in my example i have 2 basic expressions (a)* and 123. (Since its c++ string \\n file:///\\n will be taken as \n internally. I had debugged the code and i can see value of variable pattern as "(a)*\n123" in watch window). Presence of any should give me bool b as true. And my data is "aaa". So it should give true. But i am getting false. Can anyone help me to find what's wrong with my code? Thanks & Regards, Asmita EDISPHERE Software Private Limited Email: asmita.gaikwad@edisphere.com| Website: http://www.edisphere.com/ http://www.edisphere.com