Why do I need to press CTRL+D twice to break out of `while ((c=getchar())!=EOF)` in Ubuntu 14.10?

Question

I am new to C Programming and Ubuntu. I was reading the \"The C Programming Language\" by D.M Ritchie where I found the following code:

#include 

        

Answer 1

Quoting @Veritas's comment,

On linux Ctrl-D only works when the buffer is already empty otherwise it just flushes it. Therefore unless he has pressed enter without any characters after that, he will have to press Ctrl-D twice.

This explains the issue. You have to press it twice because you , after typing Hello, did not press the Enter to flush the input into the stdin. So the first time you press CTRL+D, it flushes the data into the stdin. The second time you press it, EOF is sent.