‘js_event’ undeclared, linux/joystick.h

samel_tvom · 10-06-2006, 06:35 PM

Hi!

I have a small program that doesn't do much:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <linux/joystick.h>

int main() {
	int len;
	js_event msg;
	
	while(1) {
		read(f, &msg, sizeof(js_event));
		if (len == (int) sizeof(js_event)) {
			printf("wii\n");
		}
	}
	
	return 0;

}

I try compile with gcc test.c but I get
‘js_event’ undeclared (first use in this function)

What args should I have for gcc?

Thanks!

exvor · 10-09-2006, 12:11 PM

You need to include the library on the compile line for gcc

heres an example that uses the math lib

Code:

 

#include<stdio.h> 
#include<stdlib.h> 
#include<math.h> 

int main() 
{ 
  .....some code that uses math.h 
}

to compile use

Code:

 
user@linux# gcc -o test test.c -lm

Hope this helps

samel_tvom · 10-09-2006, 03:08 PM

Thanks for the reply!

Actually, I just missed to type "struct" before "js_event", that solved it all.
I didn't have to pass anything to gcc since linux/joystick.h lives at
/usr/include, and gcc always looks there,
so

Code:

gcc testjoystick.c

Now the code looks like

Code:

// for printf
#include <stdio.h>
// for usleep
#include <unistd.h>
// for open()
#include <fcntl.h>   
// for js_event
#include <linux/joystick.h>

int main() {
	struct js_event msg;
	char* device = "/dev/input/js0";
	
	int fd = open(device, O_RDONLY);
	
	while(1) {
		if(read(fd, &msg, sizeof(struct js_event)) != sizeof(struct js_event)) {
			printf("Error when reading from joystick\n");
			exit(1);
		} else {
			printf("wee\n");
			if(msg.type == JS_EVENT_BUTTON) 
				printf("button press\n");
			if(msg.type == JS_EVENT_AXIS)
				printf("axis pressed\n");	
			usleep(10000);
		}
	}
	
	return 0;
}

As you can see when you run the program, "wee" is printed many times even though
you don't press any keys, that's probably some info stuff or something.

Well, now I know what I need to. Thanks!