If you want to implement this sort of semaphore access (which is usually what is needed if doing ipc) one thing you can do is create shared memory which is simply an int. Use this int between processes as the value of the semaphore. You can write wrapper functions which use this to allow you to do the desired readers-writers stuff or just use the shared memory plain. I wouldn't be too worried about race conditions in this case as the shared memory is only an int. If you are worried about race conditions, the wrapper functions for doing the semaphore stuff could actually use a semaphore to elimate any race conditions. Also, an added bonus of doing it this way is you can check the value of the int.
sem_get