Using getchar() in a while loop

Question

#include <stdio.h>
main()
{
    int c ;
    while ((c = getchar()) != EOF)
    {
        int isEOF = (c==EOF);
        printf("is %c EOF: %d ", c, isEOF);
    }
}

Why printf() method is called twice on every input char here?

If i give a input 'a', I am getting the result like

E:\C_workouts>gcc CharIO.c -o CharIO.exe

E:\C_workouts>CharIO.exe
a
is a EOF: 0 is
 EOF: 0

The same happens on every input.

Answer 1

Because in some implementations of getchar() when you press the key 'x' and ENTER, there are two caracters in the buffer (the 'x' and a newline char). (I know, this is a little dumb) You should skip newlines in your loop.

Update: this was already answered here: http://stackoverflow.com/questions/1004314/getchar-question

Answer 2

This should work...

    int c ;
    while (((c=getchar())^EOF)) 
        printf("is %c EOF: %d ", c, c^EOF?0:1);