Using fork(), how can I make child process run always first?

Question

Child and parent process execution is parallel and which starts first depends on OS scheduling. But what can be done to start child always before the parent?

This is

Answer 1

Use a binary semaphore with initial value 0. After fork, parent should wait on the semaphore. After child starts, it can signal the semaphore (i.e., make it 1). Then, parent's wait would be over and it will progress.