Creating an atoi function

atoi, c, function

Solution

You're declaring an array of `char *`, that is, an array of strings, rather than a single string. You probably want:

char number[MAXSIZE];

Your `scanf` format string is wrong. If you want to read a string, you should use `%s`. `%c` reads only a single character.

Your `scanf` parameter is wrong - pass `number` itself (or `&number[0]` if you prefer), not `&number`.

The parameter you're passing to `atoi_me` is wrong. Call it with `number` (or equivalently `&number[0]`), not `*number`.

Putting all of that together, you should have a `main` routine something like this:

int main(void)
{
    char number[MAXSIZE];
    int num;
    printf("Please enter a number: ");
    scanf("%s", number);
    num = atoi_me(number);
    printf("%d\n", num);
    return 0;
}

Editorial notes: You have a potential buffer overflow with the `scanf` line. You'd be better off using a function like `fgets(3)` that makes it easy to protect against that kind of problem.

`atoi(3)` also traditionally supports negative numbers (with a leading `-`) and an optional leading `+` for positive numbers, which your implementation doesn't handle.

Problem

I'm attempting to create my own atoi function. With the following I'm getting a return value of 0. Whatever I change the number variable within the function is what I get as a return value. Any suggestions on modifying the code? ``` //my atoi function int atoi_me(char *numstring) { int number = 0; while((*numstring >= '0') && (*numstring <= '9')) { number = (number * 10) + (*numstring - '0'); numstring++; } return number; } int main() { char *number[MAXSIZE]; int num; printf("Please enter a number:\n"); scanf("%c", &number); num = atoi_me(*number); printf("%d", num); return 0; } ```

Original source