wemosspiffs.txt

#include <FS.h>
 
const char* filename = "/testfile.txt";
  
void setup() 
{
  //init serial
  Serial.begin(115200);
  Serial.println();
  //Initialize File System
  if(SPIFFS.begin())
  {
    Serial.println("SPIFFS Initialize....ok");
  }
  else
  {
    Serial.println("SPIFFS Initialization...failed");
  }
 
  //Format File System
  if(SPIFFS.format())
  {
    Serial.println("File System Formated");
  }
  else
  {
    Serial.println("File System Formatting Error");
  }
 
  //Create New File And Write Data to It
  File f = SPIFFS.open(filename, "w");
  
  if (!f) 
  {
    Serial.println("file open failed");
  }
  else
  {
      //Write data to file
      Serial.println("Writing Data to File");
      f.print("This is sample data which is written to sample file");
      f.close();  //Close file
  }
 
}
 
void loop() 
{
  int i;
  
  //Read File data
  File f = SPIFFS.open(filename, "r");
  
  if (!f) 
  {
    Serial.println("file open failed");
  }
  else
  {
      Serial.println("Reading Data from File:");
      //Data from file
      for(i=0;i<f.size();i++) //Read upto complete file size
      {
        Serial.print((char)f.read());
      }
      f.close();  //Close file
      Serial.println("File Closed");
  }
  delay(5000);
}