std::basic_fstream<CharT,Traits>::swap

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (deprecated in C++98)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (deprecated in C++98)

ostrstream (deprecated in C++98)

strstream (deprecated in C++98)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_fstream

Member functions

basic_fstream::basic_fstream

basic_fstream::operator= (C++11)

basic_fstream::swap (C++11)

basic_fstream::rdbuf

File operations

basic_fstream::is_open

basic_fstream::open

basic_fstream::close

Non-member functions

swap(std::basic_fstream) (C++11)

 

void swap( basic_fstream& other );		(since C++11)

Exchanges the state of the stream with those of other.

This is done by calling basic_iostream<CharT, Traits>::swap(other) and rdbuf()->swap(other.rdbuf()).

Parameters

other

-

stream to exchange the state with

Return value

(none)

Exceptions

May throw implementation-defined exceptions.

Example

Run this code

#include <fstream>
#include <iomanip>
#include <iostream>
#include <string>
 
bool create_stream(std::fstream& fs, const std::string& path) {
    try {
        std::fstream fst { path, std::ios::trunc | std::ios::in | std::ios::out };
        if (fst.is_open()) {
            fst.swap( fs );
            return true;
        }
    } catch (...) {
        std::cout << "Exception!\n";
    }
    return false;
}
 
void use_stream(std::fstream& fs) {
    fs.seekg(0);
    std::string data;
    fs >> data;
    std::cout << "data: " << std::quoted(data) << '\n';
}
 
int main() {
    std::fstream fs;
    std::string path = "/tmp/test_file.txt";
    if (create_stream(fs, path)) {
        fs.write(path.c_str(), path.length());
        use_stream(fs);
    }
}

Possible output:

data: "/tmp/test_file.txt"

See also

operator= (C++11)	moves the file stream (public member function)
swap (C++11)	swaps two basic_filebuf objects (public member function of std::basic_filebuf<CharT,Traits>)