Managing Shared Memory in C on OSX
Perhaps a bit late, but there are cmdline tools available to do exactly this. ipcs and ipcrm
take a look at their man pages.
Call shmdt ("shared memory detach") on the shared memory segment in each process that holds a reference to it. Unix shared memory sections are reference counted, so when the last process detaches from them, they can be destroyed with shmctl(id, IPC_RMID, NULL).
From outside your application, the only option I can think of right now to clear your shared memory segments is:
for (int id=0; id < INT_MAX; id++) shmctl(id, IPC_RMID, NULL);but this is a horribly inefficient kludge. (I'm also not sure if it works; it doesn't on Linux, but Linux violates the Unix standard while MacOS X is certified against it.)