virtual int sync()
If a put area exists (e.g. the file was opened for writing), calls overflow() to write all pending output to the file.
If a get area exists (e.g. the file was opened for reading), the effect is implementation-defined. Typical implementation may empty out the get area and move the current file position back by the corresponding number of bytes.
 Return value
0 in case of success, -1 in case of failure.
|This section is incomplete
Reason: no example
 See also
| invokes sync()
(public member function of
| synchronizes an output stream with the actual file