std::literals::string_view_literals:: operator""sv

From cppreference.com
C++
Strings library
std::basic_string_view
Defined in header <string_view>
constexpr std:: string_view
operator "" sv ( const char * str, std:: size_t len ) noexcept ;
(1) (since C++17)
constexpr std:: u8string_view
operator "" sv ( const char8_t * str, std:: size_t len ) noexcept ;
(2) (since C++20)
constexpr std:: u16string_view
operator "" sv ( const char16_t * str, std:: size_t len ) noexcept ;
(3) (since C++17)
constexpr std:: u32string_view
operator "" sv ( const char32_t * str, std:: size_t len ) noexcept ;
(4) (since C++17)
constexpr std:: wstring_view
operator "" sv ( const wchar_t * str, std:: size_t len ) noexcept ;
(5) (since C++17)

Forms a string view of a character literal.

1) Returns std:: string_view { str, len } .
2) Returns std:: u8string_view { str, len } .
3) Returns std:: u16string_view { str, len } .
4) Returns std:: u32string_view { str, len } .
5) Returns std:: wstring_view { 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 std::basic_string_view literal.

Notes

These operators are declared in the namespace std::literals::string_view_literals , where both literals and string_view_literals are inline namespaces. Access to these operators can be gained with any of:

  • using namespace std :: literals ,
  • using namespace std :: string_view_literals , or
  • using namespace std :: literals :: string_view_literals .

Example

Run this code 
#include <iostream>
#include <string_view>
#include <typeinfo>
 
void print_each_character(const std::string_view sw)
{
    for (char c : sw)
        std::cout << (c == '\0' ? '@' : c);
    std::cout << '\n';
}
 
int main()
{
    using namespace std::literals;
 
    std::string_view s1 = "abc\0\0def";
    std::string_view s2 = "abc\0\0def"sv;
 
    std::cout << "s1.size(): " << s1.size() << "; s1: ";
    print_each_character(s1);
    std::cout << "s2.size(): " << s2.size() << "; s2: ";
    print_each_character(s2);
 
    std::cout << "substr(1, 4): " << "abcdef"sv.substr(1, 4) << '\n';
 
    auto value_type_info = []<typename T>(T)
    {
        using V = typename T::value_type;
        std::cout << "sizeof " << typeid(V).name() << ": " << sizeof(V) << '\n';
    };
 
    value_type_info("char A"sv);
    value_type_info(L"wchar_t ∀"sv);
    value_type_info(u8"char8_t ∆"sv);
    value_type_info(u"char16_t ∇"sv);
    value_type_info(U"char32_t ∃"sv);
    value_type_info(LR"(raw ⊞)"sv);
}

Possible output: 

s1.size(): 3; s1: abc
s2.size(): 8; s2: abc@@def
substr(1, 4): bcde
sizeof char: 1
sizeof wchar_t: 4
sizeof char8_t: 1
sizeof char16_t: 2
sizeof char32_t: 4
sizeof wchar_t: 4

See also

constructs a basic_string_view
(public member function)
(C++14)
converts a character array literal to basic_string
(function)
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