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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Strings library

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23)   basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) 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) 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

Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)  basic_string::swap Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Operations basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::substr

Constants basic_string::npos Non-member functions operator+ swap(std::basic_string) 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 conversions 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) Literals operator""s (C++14) Helper classes hash<std::basic_string> (C++11) Deduction guides(C++17)

 

size_type size()const;	(1)	(noexcept since C++11) (constexpr since C++20)
size_type length()const;	(2)	(noexcept since C++11) (constexpr 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 pointsassert(8== a.size());// 8 code units in UTF-32   std::u16string b(u"ハロー・ワールド");// 8 code pointsassert(8== b.size());// 8 code units in UTF-16   std::string c("ハロー・ワールド");// 8 code pointsassert(24== c.size());// 24 code units in UTF-8   #if __cpp_lib_char8_t >= 201907Lstd::u8string d(u8"ハロー・ワールド");// 8 code pointsassert(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	returns the number of characters (public member function of std::basic_string_view<CharT,Traits>)