ESP_SSIFFS

#include "FS.h"

void setup()
{
 // SPIFFS.format();
  Serial.begin(115200);
  bool result = SPIFFS.begin();             // always use this to "mount" the filesystem
  Serial.println("SPIFFS opened: " + result);
  File f = SPIFFS.open("/g.txt", "r");      // this opens the file "f.txt" in read-mode
  if (!f)
  {
    Serial.println("File doesn't exist yet. Creating it");
    File f = SPIFFS.open("/g.txt", "w");          // open the file in write mode
    if (!f)
    {
      Serial.println("file creation failed");
    }
    f.println("ssid=abc");                        // now write two lines in key/value style with  end-of-line characters
    f.println("password=123455secret");
  }
  else
  {
    while (f.available())                         // we could open the file
    {
      String line = f.readStringUntil('\n');      //Lets read line by line from the file
      Serial.println(line);
    }
  }
  f.close();
}
//------------------------------------
void loop() {
  // nothing to do for now, this is just a simple test
}