How to get filesize in LittleFS (ESP32/PlatformIO)

After you have initialized LittleFS (see ESP32 Filesystem initialization code example (LittleFS)) you can get the filesize by first opening the file, and then calling .size() on the opened file. Don’t forget to close the file afterwards.

auto file = LittleFS.open(filename, "r");
size_t filesize = file.size();
// Don't forget to clean up!
file.close();

Utility function to get the size of a file stored on LittleFS:

size_t LittleFSFilesize(const char* filename) {
  auto file = LittleFS.open(filename, "r");
  size_t filesize = file.size();
  // Don't forget to clean up!
  file.close();
  return filesize;
}

Example usage:

Serial.println(LittleFSFilesize("/cert.pem"));