27 Input/output library [input.output]

27.9 File-based streams [file.streams]

27.9.3 Class template basic_­ifstream [ifstream]

27.9.3.3 Member functions [ifstream.members]

basic_filebuf<charT, traits>* rdbuf() const;
Returns: const_­cast<basic_­filebuf<charT, traits>*>(&sb).
bool is_open() const;
Returns: rdbuf()->is_­open().
void open(const char* s, ios_base::openmode mode = ios_base::in); void open(const filesystem::path::value_type* s, ios_base::openmode mode = ios_base::in); // wide systems only; see [fstream.syn]
Effects: Calls rdbuf()->open(s, mode | ios_­base::in).
If that function does not return a null pointer calls clear(), otherwise calls setstate(failbit) (which may throw ios_­base::failure) ([iostate.flags]).
void open(const string& s, ios_base::openmode mode = ios_base::in); void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in);
Effects: Calls open(s.c_­str(), mode).
void close();
Effects: Calls rdbuf()->close() and, if that function returns a null pointer, calls setstate(failbit) (which may throw ios_­base::failure) ([iostate.flags]).