SVIPC(7)                  (2020-04-11)                   SVIPC(7)

     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 identi-
               fier 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, includ-
               ing 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.

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          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 call-
               ing 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).

     SEE ALSO
          ipcmk(1), ipcrm(1), ipcs(1), lsipc(1), ipc(2), msgctl(2),
          msgget(2), msgrcv(2), msgsnd(2), semctl(2), semget(2),
          semop(2), shmat(2), shmctl(2), shmdt(2), shmget(2), ftok(3),
          ipc_namespaces(7)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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