std::basic_ifstream::open

void open( const char *filename, ios_base::openmode mode = ios_base::in );	(1)
void open( const std::string &filename, ios_base::openmode mode = ios_base::in );	(2)	(since C++11)

Opens and associates the file with name filename with the file stream.

Calls setstate(failbit) on failure.

Calls clear() on success. (since C++11)

1) Effectively calls rdbuf()->open(filename, mode | ios_base::in). (see std::basic_filebuf::open for the details on the effects of that call)

2) Effectively calls (1) as if by open(filename.c_str(), mode).

filename - the name of the file to be opened

mode

specifies stream open mode. It is bitmask type, the following constants are defined:

Constant	Explanation
`app`	seek to the end of stream before each write
`binary`	open in binary mode
`in`	open for reading
`out`	open for writing
`trunc`	discard the contents of the stream when opening
`ate`	seek to the end of stream immediately after open

(none).

is_open	checks if the stream has an associated file (public member function)
close	closes the associated file (public member function)
open	opens a file and configures it as the associated character sequence (public member function of `std::basic_filebuf`)