read int/long from sd card

Here is basic example, hope it helps

No. It suffers some of the same problems as OP's code. The result variable is NOT a string, since it is not NULL terminated. Therefore, is can not be passed to a function that expects a string.

There is no checking that there is room in results for the new character, so it is quite possible that you will write beyond the end of the array.

That code is not reading data from the file.