Getting a wrong output when printing a dynamic array

Question

I'm trying to input an array length from user, and the output the numbers..

I get only "1", "1", "1" as output when n = 3, and num's values are integers.

int main()
{
    int *arr1, n,num = 0,*p;
    printf("Please enter the size of the array: ");
    scanf("%d", &n);
    arr1 = (int*)malloc(n * sizeof(int));
    if (arr1 == NULL)
        printf("Not enough memory\n");
    else  printf("Array was allocated!\n" );
    for (p = arr1; p < arr1 + n; p++)
    {
        *p = scanf("%d", &num);
        printf("%d ", *p);
    }

    free(arr1);
    getch();
}

For future reference, when posting a question regarding unexpected output, besides telling us the actual output also include the expected output, as well as the input. Please read about how to ask good questions. — Some programmer dude
– Some programmer dude, Commented Dec 26, 2015 at 17:32

cadaniluk · Accepted Answer · 2015-12-26 17:29:46Z

4

scanf returns the number of matches. num contains the entered integer.
From man scanf:

Return Value

These functions return the number of input items successfully matched and assigned [...]

Replace

*p = scanf("%d", &num);

with

scanf("%d", &num);
*p = num;

or simply¹

scanf("%d", p);

to make it work properly.

_{¹ Thanks to @JoachimPileborg!}

edited Dec 26, 2015 at 17:29

answered Dec 26, 2015 at 17:25

cadaniluk

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5 Comments

Some programmer dude Over a year ago

Or simply scanf("%d", p);

Ilan Aizelman WS Over a year ago

Why while (arr1 < arr1 +n) { scanf("%d", arr1); } doesn't work? @JoachimPileborg

Some programmer dude Over a year ago

@IlanAizelmanWS That code will work very well, if you want an infinite loop. You don't increase an1 anywhere in the loop.

Ilan Aizelman WS Over a year ago

@JoachimPileborg Still does not work. while (arr1 < arr1 + n) { scanf("%d", arr1); arr1++; } It just continues asking for more input.

Juan Carlos Coto Over a year ago

@IlanAizelmanWS because arr1 will ALWAYS be lesser than arr1 + n. Note that as arr1 increases, so does arr1 + n. You need a limit that is independent of arr1.

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