//MOSI - pin 11
//MISO - pin 12
//CLK - pin 13
//CS - pin 4 

#include <SPI.h>
#include <SD.h>

const char* fileName = "test.txt";
File myFile;

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.print("Initializing SD card...");
  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");

  myFile = SD.open(fileName, FILE_WRITE); //O_APPEND, O_CREATE

  if (myFile) {
    myFile.close(); // close the file
  } else {
    Serial.println("error opening file");
  }

  // re-open the file for reading:
  myFile = SD.open(fileName);
  if (myFile) {
    // read from the file until there's nothing else in it:
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    myFile.close();
  } else {
    Serial.println("error opening file");
  }
}

void loop() { }