std::ios_base::sync_with_stdio

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<metanoindex/>

Sets whether the standard std::cin, std::cout, std::cerr, std::clog, std::wcin, std::wcout, std::wcerr and std::wclog C++ streams are synchronized to the standard stdin, stdout, stderr and stdlog C streams after each input/output operation.

For a standard stream str, synchronized with the C stream f, the following pairs of functions have identical effect:

If the synchronization is turned off, the C++ standard streams are allowed to buffer their I/O independently, which may be considerably faster in some cases.

By default, all eight standard C++ streams are synchronized with their respective C streams.

It is implementation-defined if this function has any effect if called after some I/O occurred on the standard stream.

synchronization state before the call to the function

#include <iostream>
#include <cstdio>
int main()
{
    std::cout.sync_with_stdio(false);
    std::cout << "a\n";
    std::printf("b\n");
    std::cout << "c\n";
}

b
a
c

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