Question

I’m learning C in ansi c and I have a question.

I what to stop reading from the console when the user prints enter.

Ideally the user will enter this

1 2 3 4 5

and right after typing 5 the program would output

1
2
3
4
5

I have this code:

#include <stdio.h>
#include <stdlib.h>

#define SIZE 5

int main()
{
    int vector[SIZE] = {0}, number, counter = 0,i;

    while (scanf("%d", &number) != EOF  && counter < SIZE){
        vector[counter] = number;
        counter++;
    }

    for (i = 0; i < counter; i++){
        printf("%d\n", vector[i]);
    }

    return 0;
}

Now, the program if I input 1 2 3 4 5 and then hit ENTER, it does not stop and if I type 1 2 3 4 5 6 it program stops.

Two things.

I believe the condition to scan until EOF it’s not doing nothing. Second, program stops just because the counter < SIZE

So, how can I stop after user hits enter?

thanks

Answer 1

One option is to swap the order of your conditions:

while (counter < SIZE && scanf("%d", &number) != EOF){

As the conditions are evalulated left-to-right, your program waits for new input (via scanf(%d...)) before it evaluates counter < SIZE. This change would cause the program to immediately exit the while loop after the 5 is typed, BEFORE a user presses enter, as it evaluates counter < SIZE after the 5 is processed.

(If you choose this option, you will also want to print an endline character before you begin to repeat the numbers, as the user will not have pressed enter before it begins printing)

---

If you want the program to exit the loop when the user presses enter, you’ll have to change your scanf. scanf(%d... reads a digit, and an endline character is not a digit.