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std::basic_filebuf<CharT,Traits>::swap - cppreference.com

From cppreference.com

void swap( std::basic_filebuf& rhs );

 (since C++11)

Swaps the state and the contents of *this and rhs.

Parameters

rhs - another basic_filebuf

Return value

(none)

Notes

This function is called automatically when swapping std::fstream objects, it is rarely necessary to call it directly.

Example

#include <fstream>
#include <iostream>
#include <string>
 
int main()
{
    std::ifstream fin("test.in"); // read-only
    std::ofstream fout("test.out"); // write-only

    std::string s;
    getline(fin, s);
    std::cout << s << '\n'; // outputs the first line of test.in

    fin.rdbuf()->swap(*fout.rdbuf()); //swap the underlying buffers

    getline(fin, s); // fails: cannot read from a write-only filebuf
    std::cout << s << '\n'; // prints empty line
}

See also