std::match_results::size

From cppreference.com
< cpp‎ | regex‎ | match results
size_type size() const;
(since C++11)

Returns the number of submatches, i.e. std::distance(begin(), end()).

Returns 0 if *this does not represent the result of a successful match.

Parameters

(none)

Return value

The number of submatches

Exceptions

noexcept specification:  
noexcept
  

Complexity

Constant

Example

#include <iostream>
#include <regex>
#include <string>
 
int main()
{
    std::regex re("a(a)*b");
    std::string target("aaab");
    std::smatch sm;
 
    std::cout << sm.size() << '\n';
 
    std::regex_match(target, sm, re);
    std::cout << sm.size() << '\n';
}

Output:

0
2

See also

returns iterator to the beginning of the list of sub-matches
(public member function)
returns iterator to the end of the list of sub-matches
(public member function)