std::basic_ostream<CharT,Traits>::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>
using namespace std::chrono_literals;
void f()
{
std::cout << "Output from thread... ";
for (int i{1}; i != 10; ++i) {
std::this_thread::sleep_for(250ms);
std::cout << i << ' ';
// output three numbers at once;
// the effect is observable only in real-time
if (0 == (i % 3)) {
std::cout.flush();
}
}
std::cout << std::endl; // flushes as well
}
int main()
{
std::thread tr{f};
std::this_thread::sleep_for(150ms);
std::clog << "Output from main\n";
tr.join();
}
Output:
Output from main Output from thread... 1 2 3 4 5 6 7 8 9
See also
invokes sync() (public member function of std::basic_streambuf<CharT,Traits>) |
|
|
[virtual]
|
synchronizes the buffers with the associated character sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
| flushes the output stream (function template) |
|
outputs '\n' and flushes the output stream (function template) |
|
| synchronizes with the underlying storage device (public member function of std::basic_istream<CharT,Traits>) |
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