Why Doesn't My `std::cout` Print?

When std::cout Doesn't Print: Troubleshooting Buffered Streams

In C , the standard output stream (std::cout) is buffered, meaning that it accumulates data before sending it to the actual output device. This behavior can lead to unexpected situations where std::cout doesn't seem to print anything.

The Importance of Flushing

To ensure that data is displayed immediately, it's essential to flush the stream after writing to it. This can be achieved using the std::endl stream manipulator, which both outputs a newline character and flushes the stream.

std::cout << "Hello" << std::endl;

Alternatively, the std::flush stream manipulator can be used to flush the stream without outputting any additional characters.

std::cout << "Hello";
std::cout.flush();

Checking Stream Status

If flushing doesn't resolve the issue, you can check the stream's status to determine if it's operational. Several member functions are available for this purpose, including:

• std::ios::good: Returns true if the stream is ready to use.
• std::ios::bad: Returns true if a fatal error has occurred.
• std::ios::fail: Returns true if a non-fatal error has occurred.

Example

Consider the following program:

#include 

int main() {
  std::cout << "Hello" << std::endl;
  return 0;
}

If the program is executed, "Hello" will be displayed as expected. However, if the std::endl flush is removed, the output may not appear until the program terminates.

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