6.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <sys/ioctl.h>
#include <linux/cdrom.h>

int main(void)
{
    int fd, ret;

    fd = open("/dev/cdrom", O_RDONLY | O_NONBLOCK);
    if (fd == -1)
    {
        perror("open");
        return -1;
    }

    ret = ioctl(fd, CDROMEJECT);
    if (ret == -1)
    {
        perror("ioctl");
        return -1;
    }

    close(fd);

    return 0;
}