Convert String to Integer

#include <stdio.h>
#include <stdint.h>
#include <math.h>
int custom_atoi(const char *str) {
    int to_return = 0;
    int curr = 0;
    int sign = 1;
    if (str[0]== '+' || str[0] == '-') {
        sign = (str[0] == '-') ? -1:1;
        curr++;
    }
    while ( str[curr] != '\0'){
        if (str[curr] <= '9' && str[curr]>= '0') {
            to_return = (to_return * 10) + (str[curr] - '0');
            curr++;
        } else {
            break;
        }
    }
    return to_return * sign;
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    printf("%d", custom_atoi(str));
    return 0;
}