29 Input/output library [input.output]

29.9 File-based streams [file.streams]

29.9.1 Header <fstream> synopsis [fstream.syn]

namespace std {
  template<class charT, class traits = char_traits<charT>>
    class basic_filebuf;
  using filebuf  = basic_filebuf<char>;
  using wfilebuf = basic_filebuf<wchar_t>;

  template<class charT, class traits = char_traits<charT>>
    class basic_ifstream;
  using ifstream  = basic_ifstream<char>;
  using wifstream = basic_ifstream<wchar_t>;

  template<class charT, class traits = char_traits<charT>>
    class basic_ofstream;
  using ofstream  = basic_ofstream<char>;
  using wofstream = basic_ofstream<wchar_t>;

  template<class charT, class traits = char_traits<charT>>
    class basic_fstream;
  using fstream  = basic_fstream<char>;
  using wfstream = basic_fstream<wchar_t>;
}
1
#
The header <fstream> defines four class templates and eight types that associate stream buffers with files and assist reading and writing files.
2
#
[ Note
:
The class template basic_­filebuf treats a file as a source or sink of bytes.
In an environment that uses a large character set, the file typically holds multibyte character sequences and the basic_­filebuf object converts those multibyte sequences into wide character sequences.
— end note
 ]
3
#
In subclause [file.streams], member functions taking arguments of const filesystem​::​path​::​value_­type* are only be provided on systems where filesystem​::​path​::​value_­type ([fs.class.path]) is not char.
[ Note
:
These functions enable class path support for systems with a wide native path character type, such as wchar_­t.
— end note
 ]