Reading /dev/input/js0 from Java

Question

I'm trying to read /dev/input/js0 from Java but I keep getting

java.io.IOException: Invalid argument
at java.io.FileInputStream.read0(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:207)
at Test.main(Test.java:7)

My code is

import java.io.*;

final class Test {
    public static final void main(String[] args) {
            try {
                    FileInputStream in = new FileInputStream("/dev/input/js0");
                    System.out.println(in.read());
            } catch(IOException e) {
                    e.printStackTrace();
            }
    }
}

My end goal is to be able to read input from my controller but I can't even seem to read one byte. What am I doing wrong? My user does have read and write access to the file.

ctrueden · Accepted Answer · 2021-11-26 18:03:39Z

4

Wrapping the FileInputStream in a BufferedInputStream seems to fix the issue.

edited Nov 26, 2021 at 18:03

ctrueden

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answered Sep 10, 2016 at 18:55

Scoopta

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2 Comments

cain4355 Over a year ago

What did you do once you had this information? I can't seem to figure out the byte structure.

Scoopta Over a year ago

@MatthewSegreti the structure is listed here kernel.org/doc/Documentation/input/joystick-api.txt what I recommend is doing DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream("/dev/input/js0"))); and then using the DataInputStream to read data since you can easily read into int, short, and byte data types.

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