#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <errno.h>

int main(){

    int fd, i;
    ssize_t ret;
    char my_buf[12] = "Hello world";

    fd = open( "/dev/demo_cdrv", O_RDWR);
    if(fd < 0){
        printf("failed acquiring file descriptor return status %d\n", fd);
    }

    /* Write the contents of my buffer into the device */
    ret = write(fd, my_buf, 8);
    ret = read(fd, my_buf, 12);
    if( ret < 0 )
        printf("read operation failed with return status %d\n", ret);
    close(fd);
    return 0;
}