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SHMGET(2)                   BSD System Calls Manual                  SHMGET(2)

     shmget -- get shared memory area identifier

     #include <&lt;sys/types.h>&gt;
     #include <&lt;sys/ipc.h>&gt;
     #include <&lt;sys/shm.h>&gt;

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

     shmget() returns the shared memory identifier associated with the key

     A shared memory segment is created if either key is equal to IPC_PRIVATE,
     or key does not have a shared memory segment identifier associated with
     it, and the IPC_CREAT bit is set in shmflg.

     If a new shared memory segment is created, the data structure associated
     with it (the shmid_ds structure, see shmctl(2)) is initialized as fol-

     o   shm_perm.cuid and shm_perm.uid are set to the effective uid of the
         calling process.

     o   shm_perm.gid and shm_perm.cgid are set to the effective gid of the
         calling process.

     o   shm_perm.mode is set to the lower 9 bits of shmflg.

     o   shm_lpid, shm_nattch, shm_atime, and shm_dtime are set to 0

     o   shm_ctime is set to the current time.

     o   shm_segsz is set to the value of size.

     Upon successful completion a positive shared memory segment identifier is
     returned.  Otherwise, -1 is returned and the global variable errno is set
     to indicate the error.

     [EACESS]           A shared memory segment is already associated with key
                        and the caller has no permission to access it.

     [EEXIST]           Both IPC_CREAT and IPC_EXCL are set in shmflg, and a
                        shared memory segment is already associated with key.

     [ENOSPC]           A new shared memory indentifier could not be created
                        because the system limit for the number of shared mem-
                        ory identifiers has been reached.

     [ENOENT]           IPC_CREAT was not set in shmflg and no shared memory
                        segment associated with key was found.

     [ENOMEM]           There is not enough memory left to created a shared
                        memory segment of the requested size.

     shmctl(2), shmat(2), shmdt(2)

BSD                             August 17, 1995                            BSD