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

NAME
     shmget -- get shared memory area identifier

SYNOPSIS
     ##include <>
     ##include <>
     ##include <>

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

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

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

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

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

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

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

     ]o   shmlpid, shmnattch, shmatime, and shmdtime are set to 0

     ]o   shmctime is set to the current time.

     ]o   shmsegsz is set to the value of size.

RETURN VALUES
     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.

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

     [EXIST]           Both IPCREAT and IPCEXCL 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]           IPCREAT 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.

SEE ALSO
     shmctl(2), shmat(2), shmdt(2)

BSD                             August 17, 1995                            BSD