System V shared memory

System V provides an alternative mechanism for setting up shared memory, via the shmctl (), shmget (), shmat (), and shmdt () set of calls. These are not suggested for use, because

• System V entities live in a seperate namespace with seperate access permissions and adminstrative tools (e.g., ipcs).
• System V entities are not automatically cleaned up if all programs using them exit, and can be a resource management nightmare.