Using the SD library to create and remove files on a SD card

This example shows how to create and destroy a file on a SD card. Please click here for more information on the SD library.

Hardware Required

  • Arduino or Genuino board
  • Ethernet Shield (or other board with an SD slot)
  • Formatted SD card

Circuit

image developed using Fritzing. For more circuit examples, see the Fritzing project page

The Arduino or Genuino board has to be connected to the Ethernet Shield and also has a USB cable connected to the computer.

Schematics

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Code

The code below is configured for use with an Ethernet shield, which has an onboard SD slot. In the setup(), SD.begin() names pin 4 as the CS pin. This pin varies depending on the make of shield or board you are using.

In the setup(), open a new file with SD.open() named "example.txt". FILE_WRITE enables read and write access to the file, starting at the end. In this example though, immediately close the file by calling myFile.close().

After checking to make sure the file exists with SD.exists(), delete the file from the card with SD.remove.

/*
  SD card basic file example

 This example shows how to create and destroy an SD card file
 The circuit:
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4

 created   Nov 2010
 by David A. Mellis
 modified 9 Apr 2012
 by Tom Igoe

 This example code is in the public domain.

 */

#include <SPI.h>
#include <SD.h>

File myFile;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }


  Serial.print("Initializing SD card...");

  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");

  if (SD.exists("example.txt")) {
    Serial.println("example.txt exists.");
  } else {
    Serial.println("example.txt doesn't exist.");
  }

  // open a new file and immediately close it:
  Serial.println("Creating example.txt...");
  myFile = SD.open("example.txt", FILE_WRITE);
  myFile.close();

  // Check to see if the file exists:
  if (SD.exists("example.txt")) {
    Serial.println("example.txt exists.");
  } else {
    Serial.println("example.txt doesn't exist.");
  }

  // delete the file:
  Serial.println("Removing example.txt...");
  SD.remove("example.txt");

  if (SD.exists("example.txt")) {
    Serial.println("example.txt exists.");
  } else {
    Serial.println("example.txt doesn't exist.");
  }
}

void loop() {
  // nothing happens after setup finishes.
}

See Also


  • CardInfo - Get info about your SD card.
  • Datalogger - How to log data from three analog sensors to an SD card.
  • DumpFile - How to read a file from the SD card.
  • Listfiles - How print out the files in a directory on a SD card.
  • ReadWrite - How to read and write data to and from an SD card.


Last revision 2015/08/18 by SM

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