std::filesystem::u8path(3)

NAME
std::filesystem::u8path - std::filesystem::u8path

Synopsis
   Defined in header <filesystem>
   template< class Source > (1) (since C++17)
   std::filesystem::path u8path( const Source& source ); (deprecated in C++20)
   template< class InputIt > (since C++17)
   std::filesystem::path u8path( InputIt first, InputIt last (2) (deprecated in C++20)
   );
   Constructs a path p from a UTF-8 encoded sequence of chars
   or char8_ts
   (since C++20), supplied either as an std::string, or as std::string_view, or as a
   null-terminated multibyte string, or as a [first, last) iterator pair.
     * If path::value_type is char and native encoding is UTF-8, constructs a path
       directly as if by path(source) or path(first, last). Note: this is the typical
       situation of a POSIX system that uses Unicode, such as Linux.
     * Otherwise, if path::value_type is wchar_t and native encoding is UTF-16 (this is
       the situation on Windows), or if path::value_type is char16_t (native encoding
       guaranteed UTF-16) or char32_t (native encoding guaranteed UTF-32), then first
       converts the UTF-8 character sequence to a temporary string tmp of type
       path::string_type and then the new path is constructed as if by path(tmp).
     * Otherwise (for non-UTF-8 narrow character encodings and for non-UTF-16 wchar_t),
       first converts the UTF-8 character sequence to a temporary UTF-32-encoded string
       tmp of type std::u32string, and then the new path is constructed as if by
       path(tmp) (this path is taken on a POSIX system with a non-Unicode multibyte or
       single-byte encoded filesystem).

Parameters
                 a UTF-8 encoded std::string, std::string_view, a pointer to a
   source - null-terminated multibyte string, or an input iterator with char value
                 type that points to a null-terminated multibyte string
   first, last - pair of LegacyInputIterators that specify a UTF-8 encoded character
                 sequence

Type requirements
   -
   InputIt must meet the requirements of LegacyInputIterator.
   -
   The value type of Source or InputIt must be char
   or char8_t.
   (since C++20)

Return value
   The path constructed from the input string after conversion from UTF-8 to the
   filesystem's native character encoding.

Exceptions
   May throw std::bad_alloc if memory allocation fails.

Notes
   On systems where native path format differs from the generic path format (neither
   Windows nor POSIX systems are examples of such OSes), if the argument to this
   function is using generic format, it will be converted to native.

Example
// Run this code
 #include <cstdio>
 #ifdef _MSC_VER
 #include <fcntl.h>
 #include <io.h>
 #else
 #include <clocale>
 #include <locale>
 #endif
 #include <filesystem>
 #include <fstream>
 int main()
 {
 #ifdef _MSC_VER
     _setmode(_fileno(stderr), _O_WTEXT);
 #else
     std::setlocale(LC_ALL, "");
     std::locale::global(std::locale(""));
 #endif
     std::filesystem::path p(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-specific APIs
 #ifdef _MSC_VER
     if (std::FILE* f = _wfopen(p.c_str(), L"r"))
 #else
     if (std::FILE* f = std::fopen(p.c_str(), "r"))
 #endif
     {
         for (int ch; (ch = fgetc(f)) != EOF; std::putchar(ch))
         {}
         std::fclose(f);
     }
     std::filesystem::remove(p);
 }

Possible output:
 File contents

See also
   path represents a path
   (C++17) (class)