std::basic_string::size, std::basic_string::length
From cppreference.com
                    
                                        
                    < cpp | string | basic string
                    
                                                            
                    |   size_type size() const;  | 
||
|   size_type length() const;  | 
||
Returns the number of CharT elements in the string, i.e. std::distance(begin(), end()). 
Contents | 
[edit] Parameters
(none)
[edit] Return value
The number of CharT elements in the string.
[edit] Exceptions
| (none) | (until C++11) | 
| (since C++11) | 
[edit] Complexity
Constant
[edit] Notes
For std::string, the elements are bytes (objects of type char), which are not the same as characters if a multibyte encoding such as UTF-8 is used.
[edit] See also
|    checks whether the string is empty   (public member function)  | |
|    returns the maximum number of characters   (public member function)  | |