Re: [Boost-users] Boost [Regex] (grep Falg) Why doesn't this patternmatch?

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".

Right, but you're *not* passing a newline separated list, you're passing a \\n which is interpreted as an escape sequence matching a newline literal. HTH, John.