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2017/09/15

ESP8266 SPIFFS - Write to and read from SPIFFS disk

This post is a quick example of how to write to and read from SPIFFS disk.

Arduino Sketch

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// Very basic Spiffs example, writing 10 strings to SPIFFS filesystem, and then read them back
// For SPIFFS doc see : https://github.com/esp8266/Arduino/blob/master/doc/filesystem.md

#include <FS.h>   // This one must be on top before all the other includes.

File f;

void setup() {
  Serial.begin(115200);
  Serial.println("\nVery basic Spiffs example, writing 10 lines to SPIFFS filesystem, and then read them back");
  Serial.print("Don't run the format (SPIFFS.format()) and write (f.print / f.println) command in a loop ");
  Serial.println("as the flash memory has limited write cycle!!");
  
  SPIFFS.begin();

  // Check to see if the file exists
  f = SPIFFS.open("/f.txt", "r");
  if (!f) {
      Serial.println("File open failed or file doesn't exist..");
      Serial.println("Please wait for SPIFFS disk to be formatted");
      SPIFFS.format();
      Serial.println("SPIFFS disk formatted.");
  }  

  // Open file for writing
  f = SPIFFS.open("/f.txt", "w");
  if (!f) {
      Serial.println("File open failed. Unable to write to SPIFFS disk.");
  } else {
      Serial.println("====== Writing to SPIFFS Disk =========");
      // write 10 strings to file
      for (int i = 1; i <= 10; i++) {
          f.print("Millis() : ");
          f.println(millis());
          Serial.println(millis());
          delay(500);
      }
  }

  f.close();

  // Open file for reading
  f = SPIFFS.open("/f.txt", "r");
  if (!f) {
      Serial.println("File open failed.");
  } else {
      Serial.println("====== Reading from SPIFFS file =======");
      // read 10 strings from file
      for (int i = 1; i <= 10; i++){
        String s = f.readStringUntil('\n');
        Serial.print(i);
        Serial.print(":");
        Serial.println(s);
      }  
  }
  f.close();
}

void loop() {
  // Do nothing..
}

The Result

1st run

2nd run

References:

SPIFFS FILE READ AND WRITE EXAMPLE
http://www.esp8266.com/viewtopic.php?f=29&t=8194

ESP8266/Arduino: Playing around with the upcoming filesystem featur
https://blog.squix.org/2015/08/esp8266arduino-playing-around-with.html
at

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