C++ Regex Library - regex_match

Description

It returns whether the target sequence matches the regular expression rgx. The target sequence is either s or the character sequence between first and last, depending on the version used.

Declaration

Following is the declaration for std::regex_match.

template <class charT, class traits>
   bool regex_match (const charT* s, const basic_regex<charT,traits>& rgx,
   regex_constants::match_flag_type flags = regex_constants::match_default);

C++11

template <class charT, class traits>
   bool regex_match (const charT* s, const basic_regex<charT,traits>& rgx,
   regex_constants::match_flag_type flags = regex_constants::match_default);

C++14

template <class charT, class traits>
   bool regex_match (const charT* s, const basic_regex<charT,traits>& rgx,
   regex_constants::match_flag_type flags = regex_constants::match_default);

Parameters

• s − It is a string with the target sequence.

• rgx − It is a basic_regex object to match.

• flags − It is used to control how rgx is matched.

• m − It is an object of a match_results type.

Return Value

It returns true if rgx is matched against the target sequence. false otherwise.

Exceptions

No-noexcept − this member function never throws exceptions.

Example

In below example for std::regex_match.

#include <iostream>
#include <string>
#include <regex>

int main () {

   if (std::regex_match ("subject", std::regex("(sub)(.*)") ))
      std::cout << "string literal matched\n";

   const char cstr[] = "subject";
   std::string s ("subject");
   std::regex e ("(sub)(.*)");

   if (std::regex_match (s,e))
      std::cout << "string object matched\n";

   if ( std::regex_match ( s.begin(), s.end(), e ) )
      std::cout << "range matched\n";

   std::cmatch cm;
   std::regex_match (cstr,cm,e);
   std::cout << "string literal with " << cm.size() << " matches\n";

   std::smatch sm;
   std::regex_match (s,sm,e);
   std::cout << "string object with " << sm.size() << " matches\n";

   std::regex_match ( s.cbegin(), s.cend(), sm, e);
   std::cout << "range with " << sm.size() << " matches\n";

  
   std::regex_match ( cstr, cm, e, std::regex_constants::match_default );

   std::cout << "the matches were: ";
   for (unsigned i=0; i<sm.size(); ++i) {
      std::cout << "[" << sm[i] << "] ";
   }

   std::cout << std::endl;

   return 0;
}

The output should be like this −

string literal matched
string object matched
range matched
string literal with 3 matches
string object with 3 matches
range with 3 matches
the matches were: [subject] [sub] [ject]