read int/long from sd card

Projects Programming
4

copy paste code have do failure...
is like this

void loop()
{
  File dataFile = SD.open ("testfile.txt", FILE_READ);
  if (dataFile)
  
  {
        int c[20] ; 
        int i;
        for (i = 0 ; i< 20; i++); // write with index on array
        c[i] = dataFile.read();
        if ( c == '\0' )
        {
           //serial_data = atol(c);
          //serial_data = "";
          
          Serial.println (c[20]);
          return;
        }