![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/07\/ESP8266-Write-Data-To-a-File-LittleFS.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nWe have a similar tutorial for ESP32 boards: ESP32: Write Data to a File (LittleFS) \u2013 Arduino IDE<\/a>.<\/p>\n\n\n\n Table of Contents<\/strong><\/p>\n\n\n\n Throughout this tutorial, we’ll cover the following topics:<\/p>\n\n\n\n We\u2019ll program the ESP8266 board using Arduino IDE. So, make sure you have the ESP8266 add-on installed. Follow the next tutorial if you haven’t already:<\/p>\n\n\n\n Additionally, make sure you’re running the latest version of the ESP8266 add-on. Go to Tools <\/strong>> Board <\/strong>> Boards Manager,<\/strong> search for ESP8266<\/strong>, and check that you’re running the latest version.<\/p>\n\n\n\n LittleFS is a lightweight filesystem created for microcontrollers that lets you access the flash memory like you would do in a standard file system on your computer, but it\u2019s simpler and more limited. You can read, write, close, and delete files and folders. Using a filesystem with the ESP8266 boards is especially useful to:<\/p>\n\n\n\n You may also like reading: Install ESP8266 NodeMCU LittleFS Filesystem Uploader in Arduino IDE<\/a>.<\/p>\n\n\n\n Before showing you how to write data to a file on LittleFS with the ESP8266, let’s take a look at an example that shows how to do practically any task that you may need when dealing with files using LittleFS.<\/p>\n\n\n\n This is the official example<\/a> from the ESP8266 core.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n This code covers the following:<\/p>\n\n\n\n This particular example also displays when a file was created and what was the last time it was written. So, you’ll need to insert your network credentials so that we can get the current time from the internet.<\/p>\n\n\n\n First, you need to include the following libraries: FS.h<\/span> to handle files, LittleFS.h<\/span> to create and access the filesystem, the time.h<\/span> to deal with time functions and the ESP8266WiFi.h<\/span> so that we can connect to the internet to retrieve the current time.<\/p>\n\n\n\n You need to insert your network credentials on the following lines:<\/p>\n\n\n\n Adjust your timezone in the following parameters. In the timezone variable insert a number accordingly to your timezone in relation to GMT. Additionally, add if your timezone uses daylight saving time.<\/p>\n\n\n\n The example provides several functions to handle files on the LittleFS filesystem. Let’s take a look at them.<\/p>\n\n\n\n The listDir()<\/span> function lists the directories on the filesystem. This function accepts as arguments the directory’s file path. This will output all files and folders inside that path and the date of creation plus the last time they were modified.<\/p>\n\n\n\n Here’s an example of how to call this function. The \/<\/span> corresponds to the root directory. The following command will list all the directories and files in the root directory.<\/p>\n\n\n\n The readFile()<\/span> function reads the content of a file and prints the content in the Serial Monitor. Pass as an argument the file path.<\/p>\n\n\n\n For example, the following line reads the content of the hello.txt<\/span> file.<\/p>\n\n\n\n To write content to a file, you can use the writeFile()<\/span> function. Pass as an argument: the file path, and the message\/data (as a const char variable). <\/p>\n\n\n\n The following line writes Hello <\/span> in the hello.txt<\/span> file.<\/p>\n\n\n\n Similarly, you can append content to a file (without overwriting previous content) using the appendFile()<\/span> function.<\/p>\n\n\n\n The following line appends the message World!\\r\\n<\/span> in the hello.txt<\/span> file. The \\n<\/span> means that the next time you write something to the file, it will be written in a new line.<\/p>\n\n\n\n You can rename a file using the renameFile()<\/span> function. Pass as arguments the LittleFS<\/span> filesystem, the original filename, and the new filename.<\/p>\n\n\n\n The following line renames the hello.txt<\/span> file to foo.txt<\/span>.<\/p>\n\n\n\n Use the deleteFile()<\/span> function to delete a file. Pass as an argument the file path of the file you want to delete.<\/p>\n\n\n\n The following line deletes the hello.txt<\/span> file from the filesystem.<\/p>\n\n\n\n In the setup()<\/span>, we start by initializing Wi-Fi.<\/p>\n\n\n\n After initializing Wi-Fi, we can set up the time.<\/p>\n\n\n\n To learn more about time functions with the ESP8266, check the following tutorials:<\/p>\n\n\n\n In the setup()<\/span>, the following lines initialize the LittleFS filesystem.<\/p>\n\n\n\n The LittleFS.begin()<\/span> function returns true<\/span> if the filesystem is initialized successfully or false<\/span> if it isn’t. <\/p>\n\n\n\n The following lines call all the functions we’ve seen previously and mount and unmount the filesystem for testing purposes<\/p>\n\n\n\n Upload the previous sketch to your ESP8266 board. After that, open the Serial Monitor and press and reset your board. If the initialization succeeds, you’ll get similar messages on the Serial Monitor.<\/p>\n\n\n As you can see, when listing files, it shows the time of creation and the last time it was written.<\/p>\n\n\n\n The previous example illustrated almost all the operations you might need to do when dealing with files on the filesystem. In this section, we’ll take a look at a more simple and specific example: how to save the content of a variable to the filesystem.<\/p>\n\n\n\n Let’s take a look at the following code.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n For this example, we’ll continuously save the value of a variable to the filesystem. As an example, we’ll save a random number, but this can be easily adjusted to save sensor readings, for example.<\/p>\n\n\n\n We start by creating a variable that will hold the random number called mydata<\/span>.<\/p>\n\n\n\n For this particular example, we just need to use the writeFile()<\/span>, appendFile()<\/span>, and readFile()<\/span> functions. So, we have those functions defined before the setup()<\/span>:<\/p>\n\n\n\n In the setup()<\/span>, we initialize the Serial Monitor for debugging purposes.<\/p>\n\n\n\n And we initialize the LittleFS filesystem:<\/p>\n\n\n\n Then, we create a file called data.txt<\/span> with the following text inside MY ESP8266 DATA<\/span>:<\/p>\n\n\n\n Something to notice about the writeFile()<\/span> function: it creates a file (if it doesn’t exist) called data.txt<\/span> with the text we define inside. <\/p>\n\n\n\n If that file already exists, the writeFile()<\/span> function will overwrite any existing contents inside that file. So, if you want to continuously add new data without replacing it, you should use the appendFile()<\/span> function after creating the file. If you want to replace the content of the file, you should use the writeFile()<\/span>.<\/p>\n\n\n\n In the loop()<\/span>, we start by attributing a random value between 0 and 1000 to the mydata<\/span> variable.<\/p>\n\n\n\n Then, we append data to the file by calling the appendFile()<\/span> function.<\/p>\n\n\n\n Notice that we concatenate the mydata<\/span> variable with “\\r\\n”<\/span> so that subsequent data is written on the next line. Because our variable is of int <\/em><\/strong>type, we need to convert it to a String before concatenating.<\/p>\n\n\n\n Additionally, then, we need to convert it to a const char using the c_str()<\/span> method:<\/p>\n\n\n\n After appending data to the file, we’ll read its content by calling the readFile()<\/span> function.<\/p>\n\n\n\n New random values are generated and added to the file every 30 seconds.<\/p>\n\n\n\n Upload the code to the ESP8266 board. Open the Serial Monitor at a baud rate of 115200. <\/p>\n\n\n\n It should initialize the filesystem, create the file and start adding a new random number to the file every 30 seconds.<\/p>\n\n\n Notice that if you restart your board, you’ll lose all your previous data. Why is that happening?<\/p>\n\n\n That happens because we’re calling the writeFile()<\/span> function in the setup()<\/span>. As we’ve explained previously, it will create a new file if it doesn’t exist, or overwrite an already existing file with the same name. To prevent that, we can add some lines to the setup()<\/span> to check whether the file already exists.<\/p>\n\n\n\n To check if a file already exists in the filesystem, we can use the exists()<\/span> method and pass as an argument the file path. You can add the following lines to the setup()<\/span> to prevent overwriting when the ESP8266 restarts:<\/p>\n\n\n\n It uses the exists()<\/span> method to check if the file already exists:<\/p>\n\n\n\n It will return true<\/span> if the file already exists or false<\/span> if it doesn’t.<\/p>\n\n\n\n If it doesn’t exist, it will create the file with the content with define.<\/p>\n\n\n\n If it already exists, it simply writes File already exists<\/span> in the Serial Monitor.<\/p>\n\n\n\n Here’s the complete example that checks if the file already exists.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n If you test this example, you’ll see that the file keeps all data even after a restart.<\/p>\n\n\n With this tutorial, you learned how to save data permanently on a file in the ESP8266 LittleFS filesystem. You learn how to create a file, append data, and read the contents of a file.<\/p>\n\n\n\n If you have a file with content that you want to save to the ESP8266, and you don’t need to add data during runtime, you may want to use the LittleFS plugin instead. It allows you to save files that you have on your sketch folder directly to the ESP8266 filesystem: Install ESP8266 NodeMCU LittleFS Filesystem Uploader in Arduino IDE<\/a><\/p>\n\n\n\n We hope you found this tutorial useful. Learn more about the ESP8266 with our resources:<\/p>\n\n\n\n In this guide, you’ll learn how to write and save data permanently to a file saved on the ESP8266 filesystem (LittleFS). LittleFS is a lightweight filesystem created for microcontrollers that … <\/p>\n\n
Prerequisites<\/h2>\n\n\n\n
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Introducing LittleFS<\/h2>\n\n\n\n
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ESP8266 with LittleFS – Handling Files and Folders<\/h2>\n\n\n\n
\/* Example showing timestamp support in LittleFS - Released into the public domain.\n Earle F. Philhower, III <earlephilhower@yahoo.com> Official example: https:\/\/github.com\/esp8266\/Arduino\/blob\/master\/libraries\/LittleFS\/examples\/LittleFS_Timestamp\/LittleFS_Timestamp.ino\n*\/\n\n\/\/ Project details: https:\/\/RandomNerdTutorials.com\/esp8266-nodemcu-write-data-littlefs-arduino\/\n\n#include <FS.h>\n#include <LittleFS.h>\n#include <time.h>\n#include <ESP8266WiFi.h>\n\n#ifndef STASSID\n#define STASSID "REPLACE_WITH_YOUR_SSID"\n#define STAPSK "REPLACE_WITH_YOUR_PASSWORD"\n#endif\n\nconst char *ssid = STASSID;\nconst char *pass = STAPSK;\n\nlong timezone = 0;\nbyte daysavetime = 1;\n\nvoid listDir(const char *dirname) {\n Serial.printf("Listing directory: %s\\n", dirname);\n\n Dir root = LittleFS.openDir(dirname);\n\n while (root.next()) {\n File file = root.openFile("r");\n Serial.print(" FILE: ");\n Serial.print(root.fileName());\n Serial.print(" SIZE: ");\n Serial.print(file.size());\n time_t cr = file.getCreationTime();\n time_t lw = file.getLastWrite();\n file.close();\n struct tm *tmstruct = localtime(&cr);\n Serial.printf(" CREATION: %d-%02d-%02d %02d:%02d:%02d\\n", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour, tmstruct->tm_min, tmstruct->tm_sec);\n tmstruct = localtime(&lw);\n Serial.printf(" LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\\n", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour, tmstruct->tm_min, tmstruct->tm_sec);\n }\n}\n\nvoid readFile(const char *path) {\n Serial.printf("Reading file: %s\\n", path);\n\n File file = LittleFS.open(path, "r");\n if (!file) {\n Serial.println("Failed to open file for reading");\n return;\n }\n\n Serial.print("Read from file: ");\n while (file.available()) { Serial.write(file.read()); }\n file.close();\n}\n\nvoid writeFile(const char *path, const char *message) {\n Serial.printf("Writing file: %s\\n", path);\n\n File file = LittleFS.open(path, "w");\n if (!file) {\n Serial.println("Failed to open file for writing");\n return;\n }\n if (file.print(message)) {\n Serial.println("File written");\n } else {\n Serial.println("Write failed");\n }\n delay(2000); \/\/ Make sure the CREATE and LASTWRITE times are different\n file.close();\n}\n\nvoid appendFile(const char *path, const char *message) {\n Serial.printf("Appending to file: %s\\n", path);\n\n File file = LittleFS.open(path, "a");\n if (!file) {\n Serial.println("Failed to open file for appending");\n return;\n }\n if (file.print(message)) {\n Serial.println("Message appended");\n } else {\n Serial.println("Append failed");\n }\n file.close();\n}\n\nvoid renameFile(const char *path1, const char *path2) {\n Serial.printf("Renaming file %s to %s\\n", path1, path2);\n if (LittleFS.rename(path1, path2)) {\n Serial.println("File renamed");\n } else {\n Serial.println("Rename failed");\n }\n}\n\nvoid deleteFile(const char *path) {\n Serial.printf("Deleting file: %s\\n", path);\n if (LittleFS.remove(path)) {\n Serial.println("File deleted");\n } else {\n Serial.println("Delete failed");\n }\n}\n\nvoid setup() {\n Serial.begin(115200);\n \/\/ We start by connecting to a WiFi network\n Serial.println();\n Serial.println();\n Serial.print("Connecting to ");\n Serial.println(ssid);\n\n WiFi.begin(ssid, pass);\n\n while (WiFi.status() != WL_CONNECTED) {\n delay(500);\n Serial.print(".");\n }\n Serial.println("WiFi connected");\n Serial.println("IP address: ");\n Serial.println(WiFi.localIP());\n Serial.println("Contacting Time Server");\n configTime(3600 * timezone, daysavetime * 3600, "time.nist.gov", "0.pool.ntp.org", "1.pool.ntp.org");\n struct tm tmstruct;\n delay(2000);\n tmstruct.tm_year = 0;\n getLocalTime(&tmstruct, 5000);\n Serial.printf("\\nNow is : %d-%02d-%02d %02d:%02d:%02d\\n", (tmstruct.tm_year) + 1900, (tmstruct.tm_mon) + 1, tmstruct.tm_mday, tmstruct.tm_hour, tmstruct.tm_min, tmstruct.tm_sec);\n Serial.println("");\n Serial.println("Formatting LittleFS filesystem");\n LittleFS.format();\n Serial.println("Mount LittleFS");\n if (!LittleFS.begin()) {\n Serial.println("LittleFS mount failed");\n return;\n }\n listDir("\/");\n deleteFile("\/hello.txt");\n writeFile("\/hello.txt", "Hello ");\n appendFile("\/hello.txt", "World!\\n");\n listDir("\/");\n\n Serial.println("The timestamp should be valid above");\n\n Serial.println("Now unmount and remount and perform the same operation.");\n Serial.println("Timestamp should be valid, data should be good.");\n LittleFS.end();\n Serial.println("Now mount it");\n if (!LittleFS.begin()) {\n Serial.println("LittleFS mount failed");\n return;\n }\n readFile("\/hello.txt");\n listDir("\/");\n}\n\nvoid loop() {\n\n}\n<\/code><\/pre>\n\t\n
How the Code Works<\/h3>\n\n\n\n
#include <FS.h>\n#include <LittleFS.h>\n#include <time.h>\n#include <ESP8266WiFi.h><\/code><\/pre>\n\n\n\n#define STASSID \"REPLACE_WITH_YOUR_SSID\"\n#define STAPSK \"REPLACE_WITH_YOUR_PASSWORD\"<\/code><\/pre>\n\n\n\nlong timezone = 0;\nbyte daysavetime = 1;<\/code><\/pre>\n\n\n\nList a directory<\/h4>\n\n\n\n
void listDir(const char *dirname) {\n Serial.printf(\"Listing directory: %s\\n\", dirname);\n\n Dir root = LittleFS.openDir(dirname);\n\n while (root.next()) {\n File file = root.openFile(\"r\");\n Serial.print(\" FILE: \");\n Serial.print(root.fileName());\n Serial.print(\" SIZE: \");\n Serial.print(file.size());\n time_t cr = file.getCreationTime();\n time_t lw = file.getLastWrite();\n file.close();\n struct tm *tmstruct = localtime(&cr);\n Serial.printf(\" CREATION: %d-%02d-%02d %02d:%02d:%02d\\n\", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour, tmstruct->tm_min, tmstruct->tm_sec);\n tmstruct = localtime(&lw);\n Serial.printf(\" LAST WRITE: %d-%02d-%02d %02d:%02d:%02d\\n\", (tmstruct->tm_year) + 1900, (tmstruct->tm_mon) + 1, tmstruct->tm_mday, tmstruct->tm_hour, tmstruct->tm_min, tmstruct->tm_sec);\n }\n}<\/code><\/pre>\n\n\n\n listDir(\"\/\");<\/code><\/pre>\n\n\n\nRead File Content<\/h4>\n\n\n\n
void readFile(const char *path) {\n Serial.printf(\"Reading file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"r\");\n if (!file) {\n Serial.println(\"Failed to open file for reading\");\n return;\n }\n\n Serial.print(\"Read from file: \");\n while (file.available()) { Serial.write(file.read()); }\n file.close();\n}<\/code><\/pre>\n\n\n\nreadFile(\"\/hello.txt\");<\/code><\/pre>\n\n\n\nWrite Content to a File<\/h4>\n\n\n\n
void writeFile(const char *path, const char *message) {\n Serial.printf(\"Writing file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"w\");\n if (!file) {\n Serial.println(\"Failed to open file for writing\");\n return;\n }\n if (file.print(message)) {\n Serial.println(\"File written\");\n } else {\n Serial.println(\"Write failed\");\n }\n delay(2000); \/\/ Make sure the CREATE and LASTWRITE times are different\n file.close();\n}<\/code><\/pre>\n\n\n\nwriteFile(\"\/hello.txt\", \"Hello \");<\/code><\/pre>\n\n\n\nAppend Content to a File<\/h4>\n\n\n\n
void appendFile(const char *path, const char *message) {\n Serial.printf(\"Appending to file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"a\");\n if (!file) {\n Serial.println(\"Failed to open file for appending\");\n return;\n }\n if (file.print(message)) {\n Serial.println(\"Message appended\");\n } else {\n Serial.println(\"Append failed\");\n }\n file.close();\n}<\/code><\/pre>\n\n\n\nappendFile(\"\/hello.txt\", \"World!\\n\");<\/code><\/pre>\n\n\n\nRename a File<\/h4>\n\n\n\n
void renameFile(const char *path1, const char *path2) {\n Serial.printf(\"Renaming file %s to %s\\n\", path1, path2);\n if (LittleFS.rename(path1, path2)) {\n Serial.println(\"File renamed\");\n } else {\n Serial.println(\"Rename failed\");\n }\n}<\/code><\/pre>\n\n\n\nrenameFile(\"\/hello.txt\", \"\/foo.txt\");<\/code><\/pre>\n\n\n\nDelete a File<\/h4>\n\n\n\n
void deleteFile(const char *path) {\n Serial.printf(\"Deleting file: %s\\n\", path);\n if (LittleFS.remove(path)) {\n Serial.println(\"File deleted\");\n } else {\n Serial.println(\"Delete failed\");\n }\n}<\/code><\/pre>\n\n\n\ndeleteFile(\"\/hello.txt\");<\/code><\/pre>\n\n\n\nInitialize Wi-Fi and Time<\/h4>\n\n\n\n
WiFi.begin(ssid, pass);\n\nwhile (WiFi.status() != WL_CONNECTED) {\n delay(500);\n Serial.print(\".\");\n}\nSerial.println(\"WiFi connected\");\nSerial.println(\"IP address: \");\nSerial.println(WiFi.localIP());<\/code><\/pre>\n\n\n\nSerial.println(\"Contacting Time Server\");\nconfigTime(3600 * timezone, daysavetime * 3600, \"time.nist.gov\", \"0.pool.ntp.org\", \"1.pool.ntp.org\");\nstruct tm tmstruct;\ndelay(2000);\ntmstruct.tm_year = 0;\ngetLocalTime(&tmstruct, 5000);\nSerial.printf(\"\\nNow is : %d-%02d-%02d %02d:%02d:%02d\\n\", (tmstruct.tm_year) + 1900, (tmstruct.tm_mon) + 1, tmstruct.tm_mday, tmstruct.tm_hour, tmstruct.tm_min, tmstruct.tm_sec);\nSerial.println(\"\");<\/code><\/pre>\n\n\n\n\n
Initialize the Filesystem<\/h4>\n\n\n\n
if(!LittleFS.begin(FORMAT_LITTLEFS_IF_FAILED)){\n Serial.println(\"LittleFS Mount Failed\");\n return;\n}<\/code><\/pre>\n\n\n\nTesting the Filesystem<\/h4>\n\n\n\n
listDir(\"\/\");\ndeleteFile(\"\/hello.txt\");\nwriteFile(\"\/hello.txt\", \"Hello \");\nappendFile(\"\/hello.txt\", \"World!\\n\");\nlistDir(\"\/\");\n\nSerial.println(\"The timestamp should be valid above\");\n\nSerial.println(\"Now unmount and remount and perform the same operation.\");\nSerial.println(\"Timestamp should be valid, data should be good.\");\nLittleFS.end();\nSerial.println(\"Now mount it\");\nif (!LittleFS.begin()) {\n Serial.println(\"LittleFS mount failed\");\n return;\n}\nreadFile(\"\/hello.txt\");\nlistDir(\"\/\");<\/code><\/pre>\n\n\n\nDemonstration<\/h3>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/07\/testing-LittleFS-ESP8266.png?resize=601%2C631&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n
\n\n\n\nESP8266 with LittleFS – How to Save Variables’ Values to a File<\/h2>\n\n\n\n
\/* Example showing timestamp support in LittleFS - Released into the public domain.\n Earle F. Philhower, III <earlephilhower@yahoo.com> Official example: https:\/\/github.com\/esp8266\/Arduino\/blob\/master\/libraries\/LittleFS\/examples\/LittleFS_Timestamp\/LittleFS_Timestamp.ino\n*\/\n\n\/\/ Project details: https:\/\/RandomNerdTutorials.com\/esp8266-nodemcu-write-data-littlefs-arduino\/\n\n#include <FS.h>\n#include <LittleFS.h>\n\nint mydata;\n\nvoid readFile(const char *path) {\n Serial.printf("Reading file: %s\\n", path);\n\n File file = LittleFS.open(path, "r");\n if (!file) {\n Serial.println("Failed to open file for reading");\n return;\n }\n\n Serial.print("Read from file: ");\n while (file.available()) { Serial.write(file.read()); }\n file.close();\n}\n\nvoid writeFile(const char *path, const char *message) {\n Serial.printf("Writing file: %s\\n", path);\n\n File file = LittleFS.open(path, "w");\n if (!file) {\n Serial.println("Failed to open file for writing");\n return;\n }\n if (file.print(message)) {\n Serial.println("File written");\n } else {\n Serial.println("Write failed");\n }\n delay(2000); \/\/ Make sure the CREATE and LASTWRITE times are different\n file.close();\n}\n\nvoid appendFile(const char *path, const char *message) {\n Serial.printf("Appending to file: %s\\n", path);\n\n File file = LittleFS.open(path, "a");\n if (!file) {\n Serial.println("Failed to open file for appending");\n return;\n }\n if (file.print(message)) {\n Serial.println("Message appended");\n } else {\n Serial.println("Append failed");\n }\n file.close();\n}\n\nvoid setup() {\n Serial.begin(115200);\n \n Serial.println("Mount LittleFS");\n if (!LittleFS.begin()) {\n Serial.println("LittleFS mount failed");\n return;\n }\n else{\n Serial.println("Little FS Mounted Successfully");\n }\n writeFile("\/data.txt", "MY ESP8266 DATA \\r\\n");\n}\n\nvoid loop() {\n mydata = random (0, 1000);\n appendFile("\/data.txt", (String(mydata)+ "\\r\\n").c_str()); \/\/Append data to the file\n readFile("\/data.txt"); \/\/ Read the contents of the file\n delay(30000);\n}\n<\/code><\/pre>\n\tint mydata;<\/code><\/pre>\n\n\n\nvoid readFile(const char *path) {\n Serial.printf(\"Reading file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"r\");\n if (!file) {\n Serial.println(\"Failed to open file for reading\");\n return;\n }\n\n Serial.print(\"Read from file: \");\n while (file.available()) { Serial.write(file.read()); }\n file.close();\n}\n\nvoid writeFile(const char *path, const char *message) {\n Serial.printf(\"Writing file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"w\");\n if (!file) {\n Serial.println(\"Failed to open file for writing\");\n return;\n }\n if (file.print(message)) {\n Serial.println(\"File written\");\n } else {\n Serial.println(\"Write failed\");\n }\n delay(2000); \/\/ Make sure the CREATE and LASTWRITE times are different\n file.close();\n}\n\nvoid appendFile(const char *path, const char *message) {\n Serial.printf(\"Appending to file: %s\\n\", path);\n\n File file = LittleFS.open(path, \"a\");\n if (!file) {\n Serial.println(\"Failed to open file for appending\");\n return;\n }\n if (file.print(message)) {\n Serial.println(\"Message appended\");\n } else {\n Serial.println(\"Append failed\");\n }\n file.close();\n}<\/code><\/pre>\n\n\n\nSerial.begin(115200);<\/code><\/pre>\n\n\n\nSerial.println(\"Mount LittleFS\");\nif (!LittleFS.begin()) {\n Serial.println(\"LittleFS mount failed\");\n return;\n}\nelse{\n Serial.println(\"Little FS Mounted Successfully\");\n}<\/code><\/pre>\n\n\n\nwriteFile(\"\/data.txt\", \"MY ESP8266 DATA \\r\\n\");<\/code><\/pre>\n\n\n\nmydata = random (0, 1000);<\/code><\/pre>\n\n\n\nappendFile(\"\/data.txt\", (String(mydata)+ \"\\r\\n\").c_str()); \/\/ Append data to the file<\/code><\/pre>\n\n\n\nString(mydata)<\/code><\/pre>\n\n\n\nString(mydata)+ \"\\r\\n\").c_str()<\/code><\/pre>\n\n\n\nreadFile(\"\/data.txt\"); \/\/ Read the contents of the file<\/code><\/pre>\n\n\n\ndelay(30000);<\/code><\/pre>\n\n\n\nDemonstration<\/h2>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/07\/Write-data-to-file-and-append-littlefs-esp8266.png?resize=601%2C674&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/07\/Write-data-to-file-and-append-littlefs-esp8266-overwrite.png?resize=601%2C507&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nESP8266 with LittleFS – Check if a file already exists<\/h3>\n\n\n\n
\/\/ Check if the file already exists to prevent overwritting existing data\nbool fileexists = LittleFS.exists(\"\/data.txt\");\nSerial.print(fileexists);\nif(!fileexists) {\n Serial.println(\"File doesn\u2019t exist\");\n Serial.println(\"Creating file...\");\n \/\/ Create File and add header\n writeFile(\"\/data.txt\", \"MY ESP8266 DATA \\r\\n\");\n}\nelse {\n Serial.println(\"File already exists\");\n}<\/code><\/pre>\n\n\n\nbool fileexists = LittleFS.exists(\"\/data.txt\");<\/code><\/pre>\n\n\n\nif(!fileexists) {\n Serial.println(\"File doesn\u2019t exist\");\n Serial.println(\"Creating file...\");\n \/\/ Create File and add header\n writeFile(\"\/data.txt\", \"MY ESP8266 DATA \\r\\n\");\n}<\/code><\/pre>\n\n\n\nelse {\n Serial.println(\"File already exists\");\n}<\/code><\/pre>\n\n\n\n\/* Example showing timestamp support in LittleFS - Released into the public domain.\n Earle F. Philhower, III <earlephilhower@yahoo.com> Official example: https:\/\/github.com\/esp8266\/Arduino\/blob\/master\/libraries\/LittleFS\/examples\/LittleFS_Timestamp\/LittleFS_Timestamp.ino\n*\/\n\n\/\/ Project details: https:\/\/RandomNerdTutorials.com\/esp8266-nodemcu-write-data-littlefs-arduino\/\n\n#include <FS.h>\n#include <LittleFS.h>\n\nint mydata;\n\nvoid readFile(const char *path) {\n Serial.printf("Reading file: %s\\n", path);\n\n File file = LittleFS.open(path, "r");\n if (!file) {\n Serial.println("Failed to open file for reading");\n return;\n }\n\n Serial.print("Read from file: ");\n while (file.available()) { Serial.write(file.read()); }\n file.close();\n}\n\nvoid writeFile(const char *path, const char *message) {\n Serial.printf("Writing file: %s\\n", path);\n\n File file = LittleFS.open(path, "w");\n if (!file) {\n Serial.println("Failed to open file for writing");\n return;\n }\n if (file.print(message)) {\n Serial.println("File written");\n } else {\n Serial.println("Write failed");\n }\n delay(2000); \/\/ Make sure the CREATE and LASTWRITE times are different\n file.close();\n}\n\nvoid appendFile(const char *path, const char *message) {\n Serial.printf("Appending to file: %s\\n", path);\n\n File file = LittleFS.open(path, "a");\n if (!file) {\n Serial.println("Failed to open file for appending");\n return;\n }\n if (file.print(message)) {\n Serial.println("Message appended");\n } else {\n Serial.println("Append failed");\n }\n file.close();\n}\n\nvoid setup() {\n Serial.begin(115200);\n \n Serial.println("Mount LittleFS");\n if (!LittleFS.begin()) {\n Serial.println("LittleFS mount failed");\n return;\n }\n else{\n Serial.println("Little FS Mounted Successfully");\n }\n \/\/ Check if the file already exists to prevent overwritting existing data\n bool fileexists = LittleFS.exists("\/data.txt");\n Serial.print(fileexists);\n if(!fileexists) {\n Serial.println("File doesn\u2019t exist");\n Serial.println("Creating file...");\n \/\/ Create File and add header\n writeFile("\/data.txt", "MY ESP8266 DATA \\r\\n");\n }\n else {\n Serial.println("File already exists");\n }\n}\n\nvoid loop() {\n mydata = random (0, 1000);\n appendFile("\/data.txt", (String(mydata)+ "\\r\\n").c_str()); \/\/Append data to the file\n readFile("\/data.txt"); \/\/ Read the contents of the file\n delay(30000);\n}\n<\/code><\/pre>\n\t![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/07\/ESP8266-write-data-file-prevent-overwrite.png?resize=601%2C597&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nWrapping Up<\/h2>\n\n\n\n
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