"\N" or '\N' or Std::Endl to Std::Cout

\n or '\n' or std::endl to std::cout?

Actually, '\n' should be the default. Unless you want to also explicitly flush the stream (and when and why would you want to do that?), there is no need to use std::endl at all.¹

Of course, many books and tutorials use std::endl as the default. That is unfortunate and might lead to serious performance bugs.

I suppose there's little difference between using '\n' or using "\n", but the latter is an array of (two) characters, which has to be printed character by character, for which a loop has to be set up, which is more complex than outputting a single character. Of course, when doing IO this rarely matters, but if in doubt, when you want to output one character literal, output a character literal, rather than a whole string literal.

A nice side-effect of doing so is that you communicate in your code that you intended to output only a single character, and not just accidentally did this.

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^{1 _{Note that std::cout is tied to std::cin by default, which leads to std::cout being flushed before any input operation, so that any prompt will be printed before the user has to input something.}}

What's the difference between std::endl and '\n'

std::ostream os;

os << std::endl; // more concise

os << '\n' << std::flush; // more explicit about flushing

Those two lines have the exact same effect.

The manual flushing is often a waste of time:

• If the output stream is line-buffered, which should be the case for std::cout if it connects to an interactive terminal and the implementation can detect that, then printing \n already flushes.

• If the output stream is paired with an input stream you read from directly afterwards (std::cout and std::cin are paired), then reading already flushes.

• If you nobody waits for the data to arrive at its destination, flushing is again just going to waste.

std::endl vs \n

The varying line-ending characters don't matter, assuming the file is open in text mode, which is what you get unless you ask for binary. The compiled program will write out the correct thing for the system compiled for.

The only difference is that std::endl flushes the output buffer, and '\n' doesn't. If you don't want the buffer flushed frequently, use '\n'. If you do (for example, if you want to get all the output, and the program is unstable), use std::endl.

Difference between endl and \n

Yes, they're different.

"\n" is just a string of length 1 that gets appended to stdout.

std::endl, instead, is an object that will cause to append the newline character ("\n") AND to flush stdout buffer. For this reason it will take more processing.

Using std::endl vs \n when cin and cout are untied

how do I ensure that the buffer doesn't get overflowed,

The output buffer doesn't "overflow". When it gets full, it is automatically flushed, i.e. its contents are written out and its length is reset to 0. This is the case whether cin / cout are tied or not.

cin and cout work properly without blocking

You normally want operations on cin / cout to block. But again, blocking vs. non-blocking I/O has nothing to do with whether cin / cout are tied.

and buffer gets flushed properly when I am not using std::endl. Does the use of "\n" automatically handles it?

Outputting '\n' only flushes the buffer if the stream is in line-buffered mode. cout is automatically put in line-buffered mode if output goes to a terminal; otherwise it is block buffered (i.e. it only gets flushed when it runs full).

In a programming competition cout usually goes to a pipe or log file, so it will be block buffered and '\n' doesn't cause a flush. However, in that situation it also doesn't matter whether prompts are displayed before input is read (which is the normal use case for tied cin / cout). Just make sure you produce the right output and let the I/O library worry about buffering. The buffer is automatically flushed when it runs full, when the stream is closed, and when your program exits. No output is lost (unless your program crashes, but then you have other things to worry about).

What is the difference between '\n' and std::endl

They will generate the same characters (i.e. a carriage return), however std::endl will also flush the stream, which could have an impact on performance if over-used when generating large amounts of output.

std::endl in a string variable?

Don't forget std::endl adds a new line and flushes the buffer.

If you simply want new lines, \n, add them to your string, using + or stream them to a stream, using << '\n'.

For example,

std::string logstring;
logstring = logstring + "Error Message" + "Number" + "Time + Date";
logstring += '\n';

What is the difference between \n and std::endl

std::endl calls flush stream while cout << "\n" does not flush the stream, so cout << "\n"; gain better performance, especially while you call it in loop.

§27.7.3.8 Standard basic_ostream manipulators

namespace std {
template <class charT, class traits>
basic_ostream<charT,traits>& endl(basic_ostream<charT,traits>& os);
}
1 Effects: Calls os.put(os.widen(’\n’)), then os.flush().

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