why 'scanf' & 'getchar' adds newline to the input?

Question

I'm trying to test this simple look up table, but can't understand why both scanf and getchar add the newline character ('\n') to the input:

const int arr[10] = {1,0,5,7,6,4,8,2,9,3};
char digit;

printf("enter digits please\n");
digit = getchar();
while ((digit>='0') && (digit<='9'))
{
    printf("%d --> %d\n",digit,arr[digit-'0']);
    digit = getchar();
}
printf("bye bye!");

when runnnig this code, both with printf or getchar() the while loop executes just once, since the newline char ('\n') is also stored in the char variable digit, & I can't figure out why.

Well, when you type input at this program, what do you type? What is the exact sequence of keys you press? — zwol, Dec 17 '21 at 01:34
When you press the Return/Enter key, `getchar()` reads a newline character. — Barmar, Dec 17 '21 at 01:36
If you want to skip those, you need to add that logic to your loop, instead of just stopping the loop. — Barmar, Dec 17 '21 at 01:37
You can also solve this by just typing all your digits on one line. — Barmar, Dec 17 '21 at 01:38

score 0 · Answer 1 · answered Dec 17 '21 at 01:52

0

When you press the Enter key, it adds a newline to the input. If you want to skip that, you need to skip that. One easy way is by using scanf with a space in the format string, which skips all whitespace. Use:

scanf(" %c", &digit);

instead of digit = getchar(); in the two places you do that.

answered Dec 17 '21 at 01:52

Chris Dodd

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Don't recommend \*scanf, they are broken as specified and should not be used *ever* – zwol Dec 17 '21 at 03:31

why 'scanf' & 'getchar' adds newline to the input?

1 Answers1