Schrödinger's file

#include "SdFat.h"

SdFatSdioEX sdcard;
File testfile;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial.println("connected at 9600");
  sdcard.begin();
  if(sdcard.exists("testfile.csv")){
    Serial.println("testfile.csv found!");
  }
  if (!sdcard.exists("testfile.csv")); {
    Serial.println(F("testfile.csv not found. Creating new file."));
    testfile = sdcard.open("testfile.csv", O_CREAT | O_WRITE);
    testfile.close();
  }
}

void loop() {

}