Arduino UNO Data Logger Shield example

sd-card.ino

// This isn't needed with official Arduino app
#include <SPI.h>

#include <SD.h>

File file;

void setup() {
  Serial.begin(9600);
  delay(50);

  pinMode(4, OUTPUT);

  if (!SD.begin()) {
    Serial.println("Initialization failed");
    return;
  }

  // Write to SD card

  file = SD.open("test2.txt", FILE_WRITE);
  if (file) {
    file.println("Hello Test 3!");
    file.close();
  } else {
    Serial.println("Error opening test.txt");
  }

  // Read from SD card

  file = SD.open("test2.txt");
  if (file) {
    while (file.available()) {
      Serial.write(file.read());
    }
    file.close();
  } else {
    Serial.println("Error opening test.txt");
  }
}

void loop() {

}