std::literals::string_literals::operator""s(3)

NAME
std::literals::string_literals::operator""s - std::literals::string_literals::operator""s

Synopsis
   Defined in header <string>
                        (since
   std::string operator""s(const char *str, C++14)
   std::size_t len); (until
                        C++20)
   constexpr std::string operator""s(const char (since
   *str, std::size_t len); C++20)
   constexpr std::u8string operator""s(const (2) (since
   char8_t *str, std::size_t len); C++20)
                        (since
   std::u16string operator""s(const char16_t C++14)
   *str, std::size_t len); (until
                        C++20)
   constexpr std::u16string operator""s(const (1) (since
   char16_t *str, std::size_t len); C++20)
                        (since
   std::u32string operator""s(const char32_t C++14)
   *str, std::size_t len); (3) (until
                        C++20)
   constexpr std::u32string operator""s(const (since
   char32_t *str, std::size_t len); (4) C++20)
                        (since
   std::wstring operator""s(const wchar_t *str, C++14)
   std::size_t len); (5) (until
                        C++20)
   constexpr std::wstring operator""s(const (since
   wchar_t *str, std::size_t len); C++20)
   Forms a string literal of the desired type.
   1) returns std::string{str, len}
   2) returns std::u8string{str, len}
   3) returns std::u16string{str, len}
   4) returns std::u32string{str, len}
   5) returns std::wstring{str, len}

Parameters
   str - pointer to the beginning of the raw character array literal
   len - length of the raw character array literal

Return value
   The string literal.

Notes
   These operators are declared in the namespace std::literals::string_literals, where
   both literals and string_literals are inline namespaces. Access to these operators
   can be gained with either
     * using namespace std::literals, or
     * using namespace std::string_literals, or
     * using namespace std::literals::string_literals.
   std::chrono::duration also defines operator""s, to represent literal seconds, but it
   is an arithmetic literal: 10.0s and 10s are ten seconds, but "10"s is a string.
   Feature-test macro: __cpp_lib_string_udls

Example

// Run this code
 #include <string>
 #include <iostream>
 void print_with_zeros(auto const note, std::string const& s)
 {
     std::cout << note;
     for (const char c : s) {
         (c ? std::cout << c : std::cout << "₀");
     }
     std::cout << " (size = " << s.size() << ")\n";
 }
 int main()
 {
     using namespace std::string_literals;
     std::string s1 = "abc\0\0def";
     std::string s2 = "abc\0\0def"s;
     print_with_zeros("s1: ", s1);
     print_with_zeros("s2: ", s2);
     std::cout << "abcdef"s.substr(1,4) << '\n';
 }

Output:
 s1: abc (size = 3)
 s2: abc₀₀def (size = 8)
 bcde

See also
   constructor constructs a basic_string
                 (public member function)
   operator""sv Creates a string view of a character array literal
   (C++17) (function)