function
<ios> <iostream>
std::unitbuf
ios_base& unitbuf (ios_base& str);
Flush buffer after insertions
Sets the unitbuf "format" flag for the str stream.
When the unitbuf flag is set, the associated buffer is flushed after each insertion operation.
This flag can be unset with the nounitbuf manipulator, not forcing flushes after every insertion.
For standard streams, the unitbuf flag is not set on initialization.
Parameters
- str
- Stream object whose format flag is affected.
Because this function is a manipulator, it is designed to be used alone with no arguments in conjunction with the insertion (<<) and extraction (>>) operations on streams (see example below).
Return Value
Argument str.
Example
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// modify unifbuf flag
#include <ios> // std::unitbuf
#include <fstream> // std::ofstream
int main () {
std::ofstream outfile ("test.txt");
outfile << std::unitbuf << "Test " << "file" << '\n'; // flushed three times
outfile.close();
return 0;
}
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Data races
Modifies str. Concurrent access to the same stream object may cause data races.
Exception safety
Basic guarantee: if an exception is thrown, str is in a valid state.