Arduino SD.open() | Arduino Reference

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LCD

• Arduino - LiquidCrystal Library for LCD
• Arduino - lcd.autoscroll()
• Arduino - lcd.begin()
• Arduino - lcd.blink()
• Arduino - lcd.clear()
• LiquidCrystal() Constructor
• Arduino - lcd.createChar()
• Arduino - lcd.cursor()
• Arduino - lcd.display()
• Arduino - lcd.home()
• Arduino - lcd.leftToRight()
• Arduino - lcd.noAutoscroll()
• Arduino - lcd.noBlink()
• Arduino - lcd.noCursor()
• Arduino - lcd.noDisplay()
• Arduino - lcd.print()
• Arduino - lcd.rightToLeft()
• Arduino - lcd.scrollDisplayLeft()
• Arduino - lcd.scrollDisplayRight()
• Arduino - lcd.setCursor()
• Arduino - lcd.write()

SD-CARD

• Arduino - SD Card Library
• Arduino File.available()
• Arduino File.close()
• Arduino File.find()
• Arduino File.findUntil()
• Arduino File.flush()
• Arduino File.isDirectory()
• Arduino File.name()
• Arduino File.openNextFile()
• Arduino File.parseFloat()
• Arduino File.parseInt()
• Arduino File.peek()
• Arduino File.position()
• Arduino File.print()
• Arduino File.println()
• Arduino File.read()
• Arduino File.readBytes()
• Arduino File.readBytesUntil()
• Arduino File.readString()
• Arduino File.readStringUntil()
• Arduino File.rewindDirectory()
• Arduino File.seek()
• Arduino File.setTimeout()
• Arduino File.size()
• Arduino File.write()
• Arduino SD.begin()
• Arduino SD.exists()
• Arduino SD.mkdir()
• Arduino SD.open()
• Arduino SD.remove()
• Arduino SD.rmdir()

Servo

• Arduino - Servo Library
• Arduino - Servo.attach()
• Arduino - Servo.attached()
• Arduino - Servo.detach()
• Arduino - Servo.read()
• Arduino - Servo.write()
• Arduino - Servo.writeMicroseconds()

DIYables_IRcontroller

• DIYables IR Controller Library
• DIYables IR Controller - DIYables_IRcontroller_17()
• DIYables IR Controller - DIYables_IRcontroller_21()
• DIYables IR Controller - begin()
• DIYables IR Controller - DIYables_IRcontroller_17.getKey()
• DIYables IR Controller - DIYables_IRcontroller_21.getKey()

DIYables_4Digit7Segment_74HC595

• DIYables 74HC595 4-Digit 7-Segment Display Library

DIYables_Keypad

• DIYables Keypad Library

UnoR4WiFi_WebServer

• Arduino Uno R4 WiFi Web Server Library Reference
• Arduino Uno R4 WiFi Multi-Page Web Server Example
• Arduino Uno R4 WiFi Query String Web Server - Dynamic URL Parameters
• Arduino Uno R4 WiFi REST API Server with JSON
• Arduino Uno R4 WiFi WebSocket Server - Real-Time Communication
• Arduino Uno R4 WiFi Web Server with Authentication - Username and Password

Arduino SD.open()

Description

The SD.open() function opens a file on the SD card. In the case the file is opened for writing, a new file will be created if it doesn't already exist (but the directory containing it must already exist).

Syntax

SD.open(filename)

SD.open(filename, mode)

Parameters

• filename: the name the file to open, which can include directories (delimited by forward slashes, /). Allowed type: char * or String
• mode: (optional) the mode in which to open the file. If it is not set, the defaults value is FILE_READ. The mode can be one of the following values:
• FILE_READ: open the file for reading, starting at the beginning of the file.
• FILE_WRITE: open the file for reading and writing, starting at the end of the file.

※ NOTES AND WARNINGS:

• The filename should follows 8.3 filename convention. If not, it may fails to open.
• If a file is not closed before openning it again, it may fails to open.

Returns

• A File object referring to the opened file. If the file couldn't be opened, this object will evaluate to false in a boolean context. For example, you can test the return value with if statement.

Example Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/reference/library/arduino-sd.open */ #include <SD.h> #define PIN_SPI_CS 4 File file; void setup() { Serial.begin(9600); if (!SD.begin(PIN_SPI_CS)) { Serial.println("SD CARD FAILED, OR NOT PRESENT!"); while (1); // don't do anything more: } file = SD.open("arduino.txt", FILE_READ); if (file) { Serial.println("SD Card: file is opened"); file.close(); } else { Serial.println("SD Card: file is failed to open"); } } void loop() { }

Tutorials

• Arduino - Micro SD Card
• Arduino - Write Variable to SD Card
• Arduino - Read Config from SD Card
• Arduino - Log Data with Timestamp to SD Card

See Also

• Arduino SD Card Library Reference
• Arduino SD.begin()
• Arduino SD.exists()
• Arduino SD.mkdir()
• Arduino SD.rmdir()
• Arduino SD.remove()
• Arduino SD.open()
• Arduino File.close()
• Arduino File.name()
• Arduino File.available()
• Arduino File.flush()
• Arduino File.peek()
• Arduino File.position()
• Arduino File.print()
• Arduino File.println()
• Arduino File.seek()
• Arduino File.size()
• Arduino File.read()
• Arduino File.write()
• Arduino File.isDirectory()
• Arduino File.openNextFile()
• Arduino File.rewindDirectory()
• Arduino File.find()
• Arduino File.findUntil()
• Arduino File.readBytes()
• Arduino File.readBytesUntil()
• Arduino File.readString()
• Arduino File.readStringUntil()
• Arduino File.parseInt()
• Arduino File.parseFloat()
• Arduino File.setTimeout()

※ ARDUINO BUY RECOMMENDATION

Arduino UNO R3

Arduino Starter Kit

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