The std::clog object is the standard logging output stream in C++. It is intended for writing informational messages, debugging information, and program logs. Unlike std::cerr, which is typically reserved for error messages, std::clog is used for general logging purposes.

The std::clog stream is buffered, meaning that output may be stored temporarily before being written to the output device. Buffering improves performance when writing large amounts of log data.

Source Code #

#include <iostream>

int main()
{
    std::cout << "Application started.\n";

    std::clog << "Log: Initializing resources.\n";
    std::clog << "Log: Loading configuration.\n";

    std::cout << "Application running.\n";

    return 0;
}

Output #

Application started.
Log: Initializing resources.
Log: Loading configuration.
Application running.

Explanation #

• std::clog is the standard logging output stream defined in the <iostream> library.
• It is commonly used to display diagnostic messages, debugging information, and application logs.
• Unlike std::cerr, std::clog is buffered, allowing multiple log messages to be grouped before they are written to the output device.
• Buffering generally improves output performance, especially when producing large amounts of logging information.
• The stream insertion operator (<<) is used with std::clog in the same way as with std::cout and std::cerr.
• Using std::clog helps separate logging information from normal program output and error messages.
• return 0; terminates the program successfully.