Random() efficiency in C++

I am writing function where I need to find the random number between 1 - 10. One of the easiest way is to use random() libc call. I am going to use this function a lot. But I don't know how efficient it will be. If any one has idea about efficiency of random() that will be a help ?

Also I notice that random() give the same pattern in 2 runs.

int main()
{
   for(int i=0;i<10;i++)
   {
    cout << random() % 10 << endl;     
   }
}

Output 1st time :- 3 6 7 5 3 5 6 2 9 1

Second time also I got same output.

Then how come it's random ?