shm(2) — 386BSD 1.0

SHM(2)                    386BSD Programmer's Manual                    SHM(2)

NAME
     shmat, shmctl, shmdt, shmget - shared memory operations

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/shm.h>

     void *
     shmat(int shmid, void *shmaddr, int shmflg)

     int
     shmctl(int shmid, int cmd, void *buf)

     int
     shmdt(void *shmaddr)

     int
     shmget(key_t key, int size, int shmflg)

DESCRIPTION
     System V defines a set of operations for shared memory that is a
     manditory part of the iBCS2 standard for Intel X86 processors.  The
     segments are either part of a global table accessible via appropriate
     permissions by all processes, or private(IPC_PRIVATE) segments known only
     to the process group. The segments are identified by a shared memory
     identifier shmid, a unique integer value returned on creation.  This
     interface is made up of the following four functions:

     The shmget() function creates a shared memory segment, entering it into
     the systems global pool of shared memory segments. If successful, a
     shared memory identifier is returned.

     The shmctl() function provides control and status operations for existing
     shared memory segments, as specified by cmd. Among them, the segments can
     be removed(IPC_RMID), protection and permissions (re)assigned(IPC_SET),
     and the details of the segment can be extracted from the
     system(IPC_STAT).

     The shmat() function attaches a shared memory segment to an address in
     the user's address space (specified by shmaddr ) to allow the segment to
     be accessed by the program as ordinary memory.

     The shmdt() function detaches a shared memory segment at the address in
     the user's address space (specified by shmaddr ).

 386BSD                        February 14, 1994                             1
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