int create_user(const char *name, User **user_ptr_add) {

    // Check whether the given name could fit in the 'name' array
    if (strlen(name) + 1 >= MAX_NAME) {
        return 2;
    }

    // Check if the given name already exists in the list
    // Move to the next item in the linked list by 'next'
    while ((**user_ptr_add).next != NULL) {
        if ((**user_ptr_add).name == name) {
            return 1;
        }
    }

    // Insert the user if the given name is valid
    // Copy the name
    strncpy((**user_ptr_add).name, name, MAX_NAME - 1);
    // Initiate the other elements
    (**user_ptr_add).first_post = NULL;
    // For the linked list of friends set the first element to NULL
    *(**user_ptr_add).friends = NULL;
    (**user_ptr_add).next = NULL;
    // Return the code if successfully run
    return 0;
}

create a user with type of struct User