Sets whether the standard C++ streams are synchronized to the standard C streams after each input/output operation.

The standard C++ streams are the following:std::cin,std::cout,std::cerr,std::clog,std::wcin,std::wcout,std::wcerr andstd::wclog.

The standard C streams are the following:stdin,stdout andstderr.

For a standard streamstr, synchronized with the C streamf, the following pairs of functions have identical effect:

In practice, this means that the synchronized C++ streams are unbuffered, and each I/O operation on a C++ stream is immediately applied to the corresponding C stream's buffer. This makes it possible to freely mix C++ and C I/O.

In addition, synchronized C++ streams are guaranteed to be thread-safe (individual characters output from multiple threads may interleave, but no data races occur).

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.

If this function is called after I/O has occurred on the standard stream, the behavior is implementation-defined: implementations range from no effect to destroying the read buffer.

[edit]Parameters

[edit]Return value

Synchronization state before the call to the function.

[edit]Example

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

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[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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