std::experimental::filesystem::path::c_str, std::experimental::filesystem::path::native, std::experimental::filesystem::path::operator string_type()

#include <clocale>
#include <cstdio>
#include <experimental/filesystem>
#include <fstream>
#include <iostream>
namespace fs = std::experimental::filesystem;
 
int main()
{
 std::setlocale (LC_ALL, "en_US.utf8");
 std::locale::global (std::locale ("en_US.utf8"));
 
 fs::path p = fs::u8path(u8"要らない.txt");
 
 // native string representation can be used with OS APIs
 std::ofstream (p) << "File contents"; // this uses operator string()
 if (std::FILE * f = std::fopen (p.c_str(), "r"))
 {
 int ch;
 while ((ch=fgetc(f))!= EOF ) putchar(ch);
 std::fclose (f);
 }
 
 // multibyte and wide representation can be used for output
 std::cout.imbue(std::locale ());
 std::cout << "\nFile name in narrow multibyte encoding: "
 << p.string() << '\n';
 
 std::wcerr.imbue(std::locale ());
 std::wcerr << "File name in wide encoding: "
 << p.wstring() << '\n';
 
 fs::remove(p);
}

File contents
File name in narrow multibyte encoding: 要らない.txt
File name in wide encoding: 要らない.txt