Why Does `getline()` Fail After Using `cin` with `>>` in C ?

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Understanding getline() in C

When using the getline() method to retrieve user input in C , it is important to remember a common issue that arises. When used immediately after using cin with the >> operator, getline() may fail to capture user input correctly.

The Problem:

Let's consider the following code snippet:

In this code, it is expected that getline() will read user input and store it in messageVar. However, in certain cases, getline() stops prematurely, leaving messageVar empty.

The Solution:

To resolve this issue, it is necessary to flush the newline character left over in the input buffer from the previous cin >> operation. This can be achieved using cin.ignore():

Reason for the Issue:

When using the >> operator, it reads input until a whitespace character (e.g., space or newline) is encountered. However, it leaves the newline character in the input buffer, causing getline() to stop reading as it interprets the newline as the end of input. By using cin.ignore(), the newline character is removed from the buffer, allowing getline() to function correctly.

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