ipcclean removes all shared memory segments and semaphore sets owned by the current user. It is intended to be used for cleaning up after a crashed PostgreSQL server (postmaster). Note that immediately restarting the server will also clean up shared memory and semaphores, so this command is of little real utility.
Only the database administrator should execute this program as it can cause bizarre behavior (i.e., crashes) if run during multiuser execution. If this command is executed while a postmaster is running, the shared memory and semaphores allocated by the postmaster will be deleted. This will result in a general failure of the backend 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. Since the postmaster can now clean up by itself, it is unlikely that ipcclean will be improved upon in the future.
The script makes assumption about the format of output of the ipcs utility which may not be true across different operating systems. Therefore, it may not work on your particular OS.