I have a doubt. I opened the kernel and I changed the directory linux-3.1.1/fs/open.c I changed the follow code in the open.c. SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode) { long ret; printk(KERN_EMERG "Testing\n"); ... } **I put this line only: `printk(KERN_EMERG "Testing");`** And I include the libraries:`` and `` So I compiled and rebooted my linux(Ubuntu). During the rebooting appeared a lot of **"Testing"** on the screen. So up to now its Ok. --------------------------------------------------------------------- But now I have a problem. I created this program in c. int main() { size_t filedesc = open("testefile2.txt",O_CREAT | O_WRONLY,0640); printf("%d",filedesc); } I compiled this program and executed and works good. But I don´t understand why the **"Testing"** didn't appeared on the shell. I mean , if when I reboot the pc appeared a lot of the word "Testing" , why this word doens´t appear when I execute the program above. Just to add I include this libraries in this code above: `unistd.h` , `fcntl.h` , `stdio.h` , `stdlib.h` Thank you guys.