NAME

std::basic_string::size, - std::basic_string::size,

Synopsis

size_type size() const; (until C++11)
size_type size() const noexcept; (since C++11)
(until C++20)
constexpr size_type size() const noexcept; (since C++20)
size_type length() const; (until C++11)
size_type length() const noexcept; (since C++11)
(until C++20)
constexpr size_type length() const noexcept; (since C++20)

Returns the number of CharT elements in the string, i.e. std::distance(begin(),
end()).

Parameters

(none)

Return value

The number of CharT elements in the string.

Complexity

Unspecified (until C++11)
Constant (since C++11)

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.

Example

// Run this code

#include <cassert>
#include <iterator>
#include <string>

int main()
{
std::string s("Exemplar");
assert(8 == s.size());
assert(s.size() == s.length());
assert(s.size() == static_cast<std::string::size_type>(
std::distance(s.begin(), s.end())));

std::u32string a(U"ハロー・ワールド"); // 8 code points
assert(8 == a.size()); // 8 code units in UTF-32

std::u16string b(u"ハロー・ワールド"); // 8 code points
assert(8 == b.size()); // 8 code units in UTF-16

std::string c("ハロー・ワールド"); // 8 code points
assert(24 == c.size()); // 24 code units in UTF-8

#if __cplusplus >= 202002
std::u8string d(u8"ハロー・ワールド"); // 8 code points
assert(24 == d.size()); // 24 code units in UTF-8
#endif
}