Currently, shared semaphores can only be created, and existing semaphores can't be opened. Shared semaphores are opened using the following command.
```
sem_open(name, O_CREAT | O_EXCL, 0600, val)
```
This will raise error if a semaphore which already exists.
This behaviour works well when the file descriptors of these semaphores can be shared with children processes.

But, it doesn't work when an unrelated process which needs access to shared semaphore tries to open it.