std::basic_ostream::flush

basic_ostream& flush();

Writes uncommitted changes to the underlying output sequence.

If rdbuf() is a null pointer, does nothing.

Otherwise, behaves as an UnformattedOutputFunction (since C++11). After constructing and checking the sentry object, calls rdbuf()->pubsync(). If the call returns -1, calls setstate(badbit).

Parameters

(none).

Return value

*this.

Exceptions

May throw std::ios_base::failure if exceptions()&badbit!=0.

Example

#include <thread>
#include <iostream>
#include <chrono>
void f()
{
    std::cout << "Output from thread...";
    std::this_thread::sleep_for(std::chrono::seconds(2));
    std::cout << "...thread calls flush()\n";
    std::cout.flush();
}
 
int main()
{
    std::thread t1(f);
    std::this_thread::sleep_for(std::chrono::seconds(1));
    std::clog << "Output from main\n";
    t1.join();
}

Output from main
Output from thread.....thread calls flush()

See also