std::filebuf::open

Parameters

filename

String with the name of the file to open.

mode

Flags describing the requested input/output mode for the file.
This is an object of the bitmask type ios_base::openmode that consists of a combination of the following constants:

value	stands for	access
ios_base::in	input	File open for reading, supporting input operations.
ios_base::out	output	File open for writing, supporting output operations.
ios_base::binary	binary	Operations are performed in binary mode rather than text.
ios_base::ate	at end	The put pointer (pptr ) starts at the end of the controlled output sequence.
ios_base::app	append	All output operations happen at the end of the file, appending to its existing contents.
ios_base::trunc	truncate	Any contents that existed in the file before it is open are discarded.

These flags can be combined with the bitwise OR operator (|).

If the mode has both ios_base::trunc and ios_base::app set, the opening operation fails. It also fails if either is set but ios_base::out is not, or if both ios_base::app and ios_base::in are set.

If the mode has both ios_base::trunc and ios_base::app set, the opening operation fails. It also fails if ios_base::trunc is set but ios_base::out is not.

Return Value

Example

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// filebuf::open()
#include <iostream>
#include <fstream>
int main () {
 std::ifstream is;
 std::filebuf * fb = is.rdbuf();
 fb->open ("test.txt",std::ios::out|std::ios::app);
 // >> appending operations here <<
 fb->close();
 return 0;
}

Data races

Exception safety

See also

filebuf::is_open

Check if a file is open (public member function)

filebuf::close

Close file (public member function)