Arduino File.readBytes()
Description
The File.readBytes() function read characters from a file into a buffer. The function terminates if the determined length has been read, or it times out (see setTimeout()).
The File.readBytes() function returns the number of bytes placed in the buffer. A 0 means no valid data was found.
The File.readBytes() function inherits from the Stream utility class.
Syntax
file.readBytes(buffer, length)
Parameter Values
- file: an instance of a class that inherits from File.
- buffer: the buffer to store the bytes in. Allowed data types: array of char or byte.
- length: the number of bytes to read. Allowed data types: int.
Return Values
- The number of bytes placed in the buffer. Data type: size_t.
Example Code
- Connect the SD Card to your your PC via an USB 3.0 SD Card Reader
Create a arduino.txt file with the below content
Hi
Arduino
- Connect SD Card to Arduino. See Arduino - Micro SD Card tutorial
- Upload below code to Arduino via Arduino IDE
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/reference/library/arduino-file.readbytes
*/
#include <SD.h>
#define PIN_SPI_CS 4
File file;
char buf[20];
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:
}
// open file for reading
file = SD.open("arduino.txt", FILE_READ);
if (file) {
int avail_len = file.available();
int read_len = file.readBytes(buf, avail_len); // read all to buffer to buffer
Serial.print("Length:");
Serial.println(read_len);
Serial.println("Content:");
Serial.println(buf);
file.close();
} else {
Serial.print(F("SD Card: error on opening file"));
}
}
void loop() {
}
- Open Serial Monitor, you will see as below:
COM6
Length:10
Content:
Hi
Arduino
Autoscroll
Clear output
9600 baud
Newline
Tutorials
See Also
※ ARDUINO BUY RECOMMENDATION
| Arduino UNO R3 | |
| Arduino Starter Kit |
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