std::endl vs n in C++

Are you unknowingly slowing down your C++ programs with a simple mistake? Many developers use std::endl and n interchangeably while writing code, but did you know that this choice can impact performance? Depending on when it is appropriate to use std::endl vs n is very important to ensure maximum efficiency when logging, loop optimizations, and outputting very fast to your terminal. Keep reading to see just how this small change can make a huge difference in your C++ code. 

Table of Contents:

• std::endl (Standard End Line)
  • When to Use std::endl
• n(Newline Character)
  • When to Use n
• Key Differences Between std::endl and n
• Performance Issues in Loops
  • Why Does std::endl Cause the Performance Issue?
• Logging in C++
  1. Using std::endl for Immediate Flushing
  2. Using n for Buffered Logging
• Best Practices for Logging in C++
• Conclusion

std::endl (Standard End Line)

std::endl is a manipulator in C++ that not only moves the cursor to a new line but also flushes the output buffer. “Flushing” refers to immediately forcing all buffered output to be written when using std::endl.

Example:

Output: 

In the above code, the “Hello, World!” is printed using the std::cout, and the std::endl breaks the line and shifts to the second line. Again, the std::cout prints the “Welcome to Intellipaat!”, where it stops the second line and moves to the next line again.

When to Use std::endl

• When you require a quick output, like with logging or debugging. 
• When you want to guarantee you see the output before it crashes and hangs
• When writing to a file where flushing is necessary.

n(Newline Character) 

As the std::endl method explained above, the n operator in C++ is used to move the cursor to the next line without flushing the output buffer. Since this n operator doesn’t force an immediate write to the output stream, this method is faster as compared to std::endl.

Example:

Output: 

In the above code, the std:: cout is used for printing the “Hello, World!” and then the operator n is used to move the cursor to the next line. In the second line, also use std::cout to print “Welcome to Intellipaat” and then n to move the cursor to the following line. The output is flushed only if the program ends or the buffer is full. 

When to Use n

• When performance is required, such as for loop iterations or when printing large documents. 
• When the buffered output is acceptable (i.e., standard output that does not need to be displayed immediately). 
• When you want to format output to the console without needing to flush frequently.

Key Differences Between std::endl and n

Performance Issues in Loops 

The choice between the std::endl and n can affect the performance while printing the output inside a loop. The reason behind affecting the performance is that every time the use of std:endl it flushes the output buffer. Where the n does not work, flushing the output buffer forces the program to write all buffered data to the console or a file immediately. This can slow down the program, especially in high-frequency operations. 

Why Does std::endl Cause the Performance Issue?

• It may cause a delay because it flushes the output buffer when we call the std::endl in the code.
• If we keep flushing the output buffer, it may cause I/O overhead.

Example for using std::endl: 

Output: 

The <chrono> header in C++ is used for time-related calculations. Here, the loop starts with 0 and lasts until 6; each element follows the std::endl statement to move to the next line and flushes the output buffer. It also records the time before starting the loop and the end of the loop. We use auto end = std::chrono::high_resolution_clock::now() for precise time calculation. At last, it prints and calculates the total time taken for the compilation. 

Example for using n: 

Output: 

Here, the loop starts with 0 and lasts until 6; each element follows the n statement to move to the next line without forcing a flush. It also records the time before starting the loop and the end of the loop. We use auto end = std::chrono::high_resolution_clock::now() for precise time calculation. At last, it prints and calculates the total time taken for the compilation. 

Logging in C++

In C++, logging is a very essential application for debugging and error-tracking. Choosing between std::endl and n affects the logging performance. Here, we can use both for logging; std::endl forces immediate flush of the output buffer, whereas n depends on the default buffer behavior.

1. Using std::endl for Immediate Flushing 

In C++, for critical debugging or logs, the std::endl makes sure the assigned logs are written to the files or console. In case of crashes or system failures, the std::endl prevents the loss of logs.  

Example: 

Output: 

The above program logs the message to log.txt, by making sure the immediate flushing using std::endl for critical debugging. This may slow down the performance of the log due to frequent flushing. 

2. Using n for Buffered Logging

Utilizing n in C++ ensures that the performance efficiency is improved and the system can buffer multiple log entries before flushing. 

Example: 

Output: 

The program in this example logs the message to log.txt for buffered output efficiency. Reducing unnecessary file flushes may improve the performance here.

Best Practices for Logging in C++

1. Use Buffered Logging(n) for Performance: By minimizing the unnecessary flushing, it minimizes the I/O overhead. 
2. Use Immediate Flushing (std::endl) When Needed: In case of crashes or debugging, make sure the logs are written immediately.
3. Redirect Logs to Files Efficiently: To improve the performance of file writing, avoid excessive flushing. 
4. Use a Dedicated Logging Library: Libraries like spdlog and Boost. Log supply more advanced features. 

Conclusion

std::endl is very efficient for debugging because it makes sure of immediate flushing, but this may slow down the performance due to I/O overhead. Likewise, the usage of n in C++  allows the buffered output. The n improves the performance efficiency by reducing unnecessary flushes. Logging is an essential application for debugging and error-tracking. Logging uses n for general performance and std::endl for immediate visibility. So, choosing the right approach is always based on the user requirements and use cases. 

You can learn more about C++ in the C++ programming language and also explore C++ Interview Questions prepared by industry experts.

“std::endl” vs “n”- FAQs