C++ clog object

❮ iostream objects

int myNum = 12;

clog << "The number " << myNum << " was given\n";

Definition and Usage

The clog object is used to log messages about the state of the program. It behaves identically to cout but it can be directed to a different destination such as a log file. clog and cerr always write to the same destination.

For more detailed usage, see the <iostream> cout object.

While clog and cerr write to the same destination, clog is buffered and cerr is not. A buffered output stores the output temporarily in a variable and does not write to the destination until certain conditions are met. Buffered outputs are more efficient because they do fewer write operations on files. If the messages are important, use cerr instead because otherwise they may be lost if the program crashes.

Note: The clog object is defined in the <iostream> header file.

More Examples

#include <iostream>
#include <fstream>
using namespace std;

int main() {
  int myNum = 12;

  // Set "info.log" as the output file for the log messages
  ofstream log("info.log");
  clog.rdbuf(log.rdbuf());
  
  // Write to the log file
  clog << "The number " << myNum << " was given\n";

  // Close the file
  log.close();
  
  return 0;
}

❮ iostream objects