c++ - How can you specify carriage return and newline character match when using boost::regex? -

i having problem boost::regex behaviour when comes matching \r , \n characters in string. communicating on serial port modem linux c++ application , receiving following message it

ati3\r\nv3.244\r\nok\r\n 

i know string correct check ascii hex values of each character returned. problem application needs strip out version number specified vx.xyz part of string. end using following boost::regex based code:

 string str_modem_fw_version_number = "";  string str_regex("ati3\r\nv(\d+[.]\d+)\r\nok\r\n");  boost::regex patt;  try  {       patt.assign(str_regex);       boost::cmatch what;       if (boost::regex_match(str_reply.c_str(), sc_what, patt)) {             str_modem_fw_version_number = string(sc_what[1].first,sc_what[1].second);       }  }  catch (const boost::regex_error& e)  {      cout << e.what() << endl;  } 

the above not work - can see string correct sure making obvious error cr , nl characters in regex. have tried following not work

 string str_regex("ati3.*(\d+[.]\d+).*");  string str_regex("ati3\\r\\nv(\d+[.]\d+)\\r\\nok\\r\\n"); 

and variations on theme think must missing basic information on how boost::regex treats nl , cr characters. have looked through boost documentation pages without success , trying here last resort before using alternative boost solve problem.

try 1 instead :

string str_regex("ati3\r\nv(\\d+[.]\\d+)\r\nok\r\n"); 

notice \ of \d escaped become \\d.

applying same change 2 alternative regular expressions should make work.

explanation :

this not problem newline or carriage return matching, rather escape sequences in string literals. \d not valid escape sequence string literal - in fact compiler warns me :

warning: unknown escape sequence: '\d' [enabled default] 

it shortcut [:digit:] recognized boost::regex. in order boost::regex library 'see' \, needs escaped.