Arduino File.write()


The File.write() function writes data to the file.

The File.write() function inherits from the Stream utility class.



file.write(buf, len)


  • file: an instance of the File class that is returned by
  • data: the byte, char, or string (char *) to write
  • buf: an array of characters or bytes
  • len: the number of elements in buf


  • Returns the number of bytes written

Example Code

/* * Created by * * This example code is in the public domain * * Tutorial page: */ #include <SD.h> #define PIN_SPI_CS 4 File file; char buf[] = "Arduino"; void setup() { Serial.begin(9600); if (!SD.begin(PIN_SPI_CS)) { Serial.println(F("SD CARD FAILED, OR NOT PRESENT!")); while (1); // don't do anything more: } SD.remove("arduino.txt"); // delete the file if existed // create new file by opening file for writing file ="arduino.txt", FILE_WRITE); if (file) { file.write('H'); // a character file.write('i'); // a character file.write('\n'); // new line file.write(buf, 7); file.close(); } else { Serial.print(F("SD Card: error on opening file arduino.txt")); } } void loop() { }

After running the above code, if you disconnect SD Cart from Arduino and connect the SD Card to your your PC, you will see a arduino.txt file with the below content

Hi Arduino


Arduino UNO R3
Arduino Starter Kit
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