System V Interprocess Communication

System V IPC Object Characteristics

System V IPC mechanisms are useful tools for performing reliable, system-wide communication, especially when flow control and priority processing are required. This section discusses characteristics and constructors of System V IPC objects, as well as the construction of public and private keys.

It is important to note the following characteristics of System V IPC objects.

• When created, the object is allocated a system-wide ID by the kernel. If a process knows the ID of a Systems V IPC object, the process constructs a reference to the object and accesses the object using its ID.
• When created, the object can be "tagged" with a public key. If a process knows the key of a Systems V IPC object, the process can construct a reference to the object and access it using the key. The os_key class can conveniently construct a key from either an integer or a <path/integer> pair.
• The object remains in the system until explicitly removed, even if the process that constructed the object terminates.
• The object stores the user and group of the object's creator, the user and group of the object's owner, and a set of permissions flags. By default, the user and group fields are set from the process that created the object.
• The object cannot be copied or assigned.