Manpages - sysvipc.7

System V message queues allow data to be exchanged in units called messages. Each messages can have an associated priority, POSIX message queues provide an alternative API for achieving the same result; see *mq_overview*(7).

The System V message queue API consists of the following system calls:

*msgget*(2)

Create a new message queue or obtain the ID of an existing message queue. This call returns an identifier that is used in the remaining APIs.

*msgsnd*(2)

Add a message to a queue.

*msgrcv*(2)

Remove a message from a queue.

*msgctl*(2)

Perform various control operations on a queue, including deletion.

System V semaphores allow processes to synchronize their actions. System V semaphores are allocated in groups called sets; each semaphore in a set is a counting semaphore. POSIX semaphores provide an alternative API for achieving the same result; see *sem_overview*(7).

The System V semaphore API consists of the following system calls:

*semget*(2)

Create a new set or obtain the ID of an existing set. This call returns an identifier that is used in the remaining APIs.

*semop*(2)

Perform operations on the semaphores in a set.

*semctl*(2)

Perform various control operations on a set, including deletion.

System V shared memory allows processes to share a region a memory (a “segment”). POSIX shared memory is an alternative API for achieving the same result; see *shm_overview*(7).

The System V shared memory API consists of the following system calls:

*shmget*(2)

Create a new segment or obtain the ID of an existing segment. This call returns an identifier that is used in the remaining APIs.

*shmat*(2)

Attach an existing shared memory object into the calling process’s address space.

*shmdt*(2)

Detach a segment from the calling process’s address space.

*shmctl*(2)

Perform various control operations on a segment, including deletion.

For a discussion of the interaction of System V IPC objects and IPC namespaces, see *ipc_namespaces*(7).