SVIPC

Section: Linux Programmer's Manual (7)
Updated: 2020-04-11
Page Index

NAME

sysvipc - System V interprocess communication mechanisms

DESCRIPTION

System V IPC is the name given to three interprocess communication mechanisms that are widely available on UNIX systems: message queues, semaphore, and shared memory.

Message queues

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.

Semaphore sets

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.

Shared memory segments

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.

IPC namespaces

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

COLOPHON

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