How to generate long (up to 25 millions) random sequence of integers in C (with no repetition)?

I need to generate long (pseudo)random arrays (1000-25 000 000 integers) where no element is repeated. How do I do it since rand() function does not generate numbers long enough?

I tried to use this idea: array[i] = (rand() << 14) | rand() % length; however I suppose there is much better way that I don't know.

Thank you for your help.