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

const value_type* c_str() const;	(1)	(since C++17)
const string_type& native() const;	(2)	(since C++17)
operator string_type() const;	(3)	(since C++17)

Accesses the native path name as a character string.

1) Equivalent to native().c_str().

2) Returns the native string representation of the pathname by reference.

3) Returns the native string representation of the pathname by value.

Parameters

(none).

Return value

The native string representation of the pathname, using native syntax, native character type, and native character encoding. This string is suitable for use with OS APIs.

Exceptions

1,2)

noexcept specification:

noexcept

Notes

The conversion function (3) is provided so that standard file-opening APIs that accept std::basic_string file names, such as the std::ifstream constructor, can use pathnames with no changes to code:

std::filesystem::path p = "/tmp/text.txt";
std::ifstream f(p);

Example

#include <cstdio>
#ifdef _MSC_VER
#include <io.h>
#include <fcntl.h>
#else
#include <locale>
#include <clocale>
#endif
#include <fstream>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
 
int main()
{
#ifdef _MSC_VER
    _setmode(_fileno(stderr), _O_WTEXT);
#else
    std::setlocale(LC_ALL, "");
    std::locale::global(std::locale(""));
    std::cout.imbue(std::locale());
    std::wcerr.imbue(std::locale());
#endif
 
    fs::path p = fs::u8path(u8"要らない.txt");
    std::ofstream(p) << "File contents"; // Prior to LWG2676 uses operator string_type()
                                         // on MSVC, where string_type is wstring, only
                                         // works due to non-standard extension.
                                         // Post-LWG2676 uses new fstream constructors
 
    // native string representation can be used with OS APIs
    if (std::FILE* f =
#ifdef _MSC_VER
                _wfopen(p.c_str(), L"r")
#else
                std::fopen(p.c_str(), "r")
#endif
        )
    {
        int ch;
        while((ch=fgetc(f))!= EOF) putchar(ch);
        std::fclose(f);
    }
 
    // multibyte and wide representation can be used for output
    std::cout << "\nFile name in narrow multibyte encoding: " << p.string() << '\n';
    std::wcerr << "File name in wide encoding: " << p.wstring() << '\n';
 
    fs::remove(p);
}

Output:

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