std::basic_string<CharT,Traits,Allocator>::size, std::basic_string<CharT,Traits,Allocator>::length

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)   Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::starts_with (C++20)   basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23) basic_string::swap

Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of Constants basic_string::npos Deduction guides (C++17) Non-member functions operator+ swap(std::basic_string) operator""s (C++14) erase(std::basic_string)erase_if(std::basic_string) (C++20)(C++20) I/O operator<<operator>> getline Comparison operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) Numeric conversion stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11) stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string>hash<std::u8string> (C++11)  (C++11)(C++11)(C++11)(C++20) hash<std::pmr::string>hash<std::pmr::wstring>hash<std::pmr::u32string>hash<std::pmr::u16string>hash<std::pmr::u8string> (C++17)(C++17)(C++17)(C++17)(C++20)

 

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
}

See also

empty	checks whether the string is empty (public member function)
max_size	returns the maximum number of characters (public member function)
sizelength (C++17)	returns the number of characters (public member function of std::basic_string_view<CharT,Traits>)