If this command is executed while postmaster is running, the shared memory and semaphores allocated by the postmaster will be deleted. This will result in a general failure of the backends servers started by that postmaster . This script is a hack, but in the many years since it was written, no one has come up with an equally effective and portable solution.
Suggestions are welcome.
The script makes assumption about the format of output of the ipcs utility which may not be true across different operating systems.