You can achieve a kind of automatic synchronization for output files by using the format flag ios_base::unitbuf. It causes an output stream to flush its buffer after each output operation as follows:
ofstream ostr("/tmp/fil");
ifstream istr("/tmp/fil");
ostr << unitbuf; //1
while (some_condition)
{ ostr << " some output"; //2
// process the output
istr >> s;
//
}
| //1 | Set the unitbuf format flag. |
| //2 | After each insertion into the shared file /tmp/fil, the buffer is automatically flushed, and the output is available to other streams that read from the same file. |
Since it is not overly efficient to flush after every single token that is inserted, you might consider switching off the unitbuf flag for a lengthy output that is not supposed to be read partially.
ostr.unsetf(ios_base::unitbuf); //1 ostr << " some lengthy and complicated output "; ostr.flush().setf(ios_base::unitbuf); //2
| //1 | Switch off the unitbuf flag. Alternatively, using manipulators, you can say ostr << nounitbuf; |
| //2 | Flush the buffer and switch on the unitbuf flag again. Alternatively, you can say ostr << flush << unitbuf; |
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