Read RFID tag ref from SD card and check match

Using Arduino Programming Questions
6

I would compare each character as it is read from the file and stop as soon as there was a mismatch.

#include "SD.h"

void setup() {}
void loop() {}

char readCard[5];

boolean rfidMatchDisp(unsigned long recIndex) {

  int result = true;      // assume success
  long rfidPosition = 0;

  File dataFile = SD.open("TAGREF.CSV", FILE_READ);        // Open the file
  dataFile.seek(recIndex + 1);                             // recIndex is from another function...

  rfidPosition = dataFile.position() + 1;                  // Index the RFID position for reading
  dataFile.seek(rfidPosition);

  // look at each character
  for (int i = 0; i < 4; i++ )  {

    // if not a match, set return value and stop looking
    if ( dataFile.read() != readCard[i])
    {
      result = false;
      break;
    }
  }

  dataFile.close();

  return (result);
}