std::basic_ifstream<CharT,Traits>:: open

void open ( const char * filename, std:: ios_base :: openmode mode = std:: ios_base :: in ) ;	(1)
void open ( const std :: filesystem :: path :: value_type * filename, std:: ios_base :: openmode mode = std:: ios_base :: in ) ;	(2)	(since C++17)
void open ( const std:: string & filename, std:: ios_base :: openmode mode = std:: ios_base :: in ) ;	(3)	(since C++11)
void open ( const std:: filesystem :: path & filename, std:: ios_base :: openmode mode = std:: ios_base :: in ) ;	(4)	(since C++17)

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

Calls clear ( ) on success. Calls setstate ( failbit ) on failure.

Parameters

filename	-	the name of the file to be opened
mode	-	specifies stream open mode. It is a BitmaskType , 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 noreplace (C++23) open in exclusive mode

Return value

(none)

Example

This section is incomplete Reason: no example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 22	C++98	it was unclear how error state changes upon a successful open	the error state is unchanged
LWG 409	C++98	the error state was unchanged upon a successful open	it is cleared [1]

1. ↑ The resolution of LWG issue #22 is overriden.

See also

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<CharT,Traits> )