Convert String to Integer

#include <stdio.h>
#include <stdint.h>

int custom_atoi(const char *str) {
    int num=0;
    int i=0;
    if(str[0]=='+'||str[0]=='-'){i++;}
    while(str[i]!='\0' ){
        if(str[i]>='0'&&str[i]<='9')
        {
            num=num*10+(str[i]-48); 
        }
        else if(str[i]!=(str[i]>='0'&&str[i]<='9')){
            if(str[0]=='-'){return num*=-1;}
            else return num;
        } 
        i++;
    }
    return num;
    
}

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;
}