std::basic_ostream<CharT,Traits>::flush (3) - Linux Manuals

std::basic_ostream<CharT,Traits>::flush: std::basic_ostream<CharT,Traits>::flush

NAME

std::basic_ostream<CharT,Traits>::flush - std::basic_ostream<CharT,Traits>::flush

Synopsis

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

// Run this code

  #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:

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