I found a nice little solution here. The C code below, minimally changed from the linked site, will return an exit code of 0 if the tray is open and 1 if it is not.

So, save this code as something (e.g. foo.c) and compile it with this command:

gcc -o trayopen foo.c

Then, copy the compiled executable, trayopen to /usr/bin:

sudo cp trayopen /usr/bin

You should no be able to do things like

trayopen /dev/sr0 && echo closed

Or, more complete:

#!/bin/sh

if trayopen /dev/sr0

then

    echo "Tray is open."

else

    echo "Tray is closed."

fi

The code:

#include <stdio.h>

#include <stdlib.h>

#include <sys/ioctl.h>

#include <fcntl.h>

#include <linux/cdrom.h>



int main(int argc,char **argv) {

  int cdrom;

  int status=1;



  if (! argv[1] ){

    printf("Usage : trayopen [device]

");

    printf("Result: Returns a 0 if the tray was open and 1 if it was closed

");

    exit(2);

  }



  if ((cdrom = open(argv[1],O_RDONLY | O_NONBLOCK)) < 0) {

    printf("Unable to open device %s. Provide a device name (/dev/sr0, /dev/cdrom) as a parameter.

",argv[1]);

    exit(2);

  }

  /* Check CD tray status */

  if (ioctl(cdrom,CDROM_DRIVE_STATUS) == CDS_TRAY_OPEN) {

    status=0;

  }



  close(cdrom);

  exit(status);

}