#include <SD.h>
#define CS_PIN 10

File root; // declare "root" as type "File"

void setup() {
  Serial.begin(115200);
  initializeSDcard();
  readDirectory();
  readFile();
}

void loop() {
  // nothing happens after setup finishes.
}

void readFile() {
  Serial.println("==================== begin READ FILE");
  File textFile = SD.open("myFile.txt");
  if (textFile) {
    Serial.println("Filename: myFile.txt: ");
    while (textFile.available()) {
      Serial.write(textFile.read());
    }
    textFile.close();
  } else {
    Serial.println("error opening myFile.txt!");
  }
  Serial.println("==================== end READ FILE");
}

void initializeSDcard() {
  Serial.print("==================== Initializing SD card... ");
  if (!SD.begin(CS_PIN)) {
    Serial.println("Card initialization failed!");
    while (true);
  }
  Serial.println("Complete.\n");
}

void readDirectory() {
  Serial.println("==================== begin READ DIRECTORY");
  Serial.println("Files in the card:");
  root = SD.open("/");
  printDirectory(root, 0);
  Serial.println("==================== end READ DIRECTORY\n");
}

void printDirectory(File dir, int numTabs) {
  Serial.println("==================== begin PRINT DIRECTORY ");
  while (true) {
    File entry =  dir.openNextFile();
    if (! entry) {
      // no more files
      break;
    }
    for (uint8_t i = 0; i < numTabs; i++) {
      Serial.print('\t');
    }
    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      printDirectory(entry, numTabs + 1);
    } else {
      // files have sizes, directories do not
      Serial.print("\t\t");
      Serial.println(entry.size(), DEC);
    }
    entry.close();
  }
  Serial.println("==================== end PRINT DIRECTORY");
}