arduino-esp32/libraries/SPIFFS/examples/SPIFFS_Test/SPIFFS_Test.ino

#include "FS.h"
#include "SPIFFS.h"

/* You only need to format SPIFFS the first time you run a
   test or else use the SPIFFS plugin to create a partition
   https://github.com/me-no-dev/arduino-esp32fs-plugin */
#define FORMAT_SPIFFS_IF_FAILED true

void listDir(fs::FS &fs, const char *dirname, uint8_t levels) {
  Serial.printf("Listing directory: %s\r\n", dirname);

  File root = fs.open(dirname);
  if (!root) {
    Serial.println("- failed to open directory");
    return;
  }
  if (!root.isDirectory()) {
    Serial.println(" - not a directory");
    return;
  }

  File file = root.openNextFile();
  while (file) {
    if (file.isDirectory()) {
      Serial.print("  DIR : ");
      Serial.println(file.name());
      if (levels) {
        listDir(fs, file.path(), levels - 1);
      }
    } else {
      Serial.print("  FILE: ");
      Serial.print(file.name());
      Serial.print("\tSIZE: ");
      Serial.println(file.size());
    }
    file = root.openNextFile();
  }
}

void readFile(fs::FS &fs, const char *path) {
  Serial.printf("Reading file: %s\r\n", path);

  File file = fs.open(path);
  if (!file || file.isDirectory()) {
    Serial.println("- failed to open file for reading");
    return;
  }

  Serial.println("- read from file:");
  while (file.available()) {
    Serial.write(file.read());
  }
  file.close();
}

void writeFile(fs::FS &fs, const char *path, const char *message) {
  Serial.printf("Writing file: %s\r\n", path);

  File file = fs.open(path, FILE_WRITE);
  if (!file) {
    Serial.println("- failed to open file for writing");
    return;
  }
  if (file.print(message)) {
    Serial.println("- file written");
  } else {
    Serial.println("- write failed");
  }
  file.close();
}

void appendFile(fs::FS &fs, const char *path, const char *message) {
  Serial.printf("Appending to file: %s\r\n", path);

  File file = fs.open(path, FILE_APPEND);
  if (!file) {
    Serial.println("- failed to open file for appending");
    return;
  }
  if (file.print(message)) {
    Serial.println("- message appended");
  } else {
    Serial.println("- append failed");
  }
  file.close();
}

void renameFile(fs::FS &fs, const char *path1, const char *path2) {
  Serial.printf("Renaming file %s to %s\r\n", path1, path2);
  if (fs.rename(path1, path2)) {
    Serial.println("- file renamed");
  } else {
    Serial.println("- rename failed");
  }
}

void deleteFile(fs::FS &fs, const char *path) {
  Serial.printf("Deleting file: %s\r\n", path);
  if (fs.remove(path)) {
    Serial.println("- file deleted");
  } else {
    Serial.println("- delete failed");
  }
}

void testFileIO(fs::FS &fs, const char *path) {
  Serial.printf("Testing file I/O with %s\r\n", path);

  static uint8_t buf[512];
  size_t len = 0;
  File file = fs.open(path, FILE_WRITE);
  if (!file) {
    Serial.println("- failed to open file for writing");
    return;
  }

  size_t i;
  Serial.print("- writing");
  uint32_t start = millis();
  for (i = 0; i < 2048; i++) {
    if ((i & 0x001F) == 0x001F) {
      Serial.print(".");
    }
    file.write(buf, 512);
  }
  Serial.println("");
  uint32_t end = millis() - start;
  Serial.printf(" - %u bytes written in %lu ms\r\n", 2048 * 512, end);
  file.close();

  file = fs.open(path);
  start = millis();
  end = start;
  i = 0;
  if (file && !file.isDirectory()) {
    len = file.size();
    size_t flen = len;
    start = millis();
    Serial.print("- reading");
    while (len) {
      size_t toRead = len;
      if (toRead > 512) {
        toRead = 512;
      }
      file.read(buf, toRead);
      if ((i++ & 0x001F) == 0x001F) {
        Serial.print(".");
      }
      len -= toRead;
    }
    Serial.println("");
    end = millis() - start;
    Serial.printf("- %u bytes read in %lu ms\r\n", flen, end);
    file.close();
  } else {
    Serial.println("- failed to open file for reading");
  }
}

void setup() {
  Serial.begin(115200);
  if (!SPIFFS.begin(FORMAT_SPIFFS_IF_FAILED)) {
    Serial.println("SPIFFS Mount Failed");
    return;
  }

  listDir(SPIFFS, "/", 0);
  writeFile(SPIFFS, "/hello.txt", "Hello ");
  appendFile(SPIFFS, "/hello.txt", "World!\r\n");
  readFile(SPIFFS, "/hello.txt");
  renameFile(SPIFFS, "/hello.txt", "/foo.txt");
  readFile(SPIFFS, "/foo.txt");
  deleteFile(SPIFFS, "/foo.txt");
  testFileIO(SPIFFS, "/test.txt");
  deleteFile(SPIFFS, "/test.txt");
  Serial.println("Test complete");
}

void loop() {}