Why does cin command leaves a '\n' in the buffer?

Question

This is related to: cin and getline skipping input But they don\'t answer the why it happens just the how to fix it.

Why does cin leaves a \'\\n\' in th

Answer 1

You are not comparing cin to cin.getline, but rather cin.operator>> and cin.getline, and that is exactly what these functions are defined to do. The answer to the question "why" is "by definition". If you want rationale, I can't give it to you.

cin.getline reads and consumes until a newline \n is entered. cin.operator>> does not consume this newline. The latter performs formatted input, skipping leading whitespace, until the end of the object it was reading (in your case whatever foo is) "stops" (in case foo is an int, when the character isn't a number). A newline is what remains when the number is consumed from the input line. cin.getline reads a line, and consumes the newline by definition.

Make sure to always check for error on each stream operation:

if(cin >> foo)

or

if(std::getline(cin, some_string))

Note I used std::getline instead of the stream's member because this way there's no need for any magic numbers (the 100 in your code).