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

NAME
     sshhmmggeett - get shared memory area identifier

SYNOPSIS
     ##iinncclluuddee <>

     int
     sshhmmggeett(keyt key, sizet size, int shmflg);

DESCRIPTION
     sshhmmggeett() 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 IPCCREAT 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:

     ++oo   shmperm.cuid and shmperm.uid are set to the effective uid of the
         calling process.

     ++oo   shmperm.gid and shmperm.cgid are set to the effective gid of the
         calling process.

     ++oo   shmperm.mode is set to the lower 9 bits of shmflg.

     ++oo   shmlpid, shmnattch, shmatime, and shmdtime are set to 0

     ++oo   shmctime is set to the current time.

     ++oo   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.

EERRRROORRSS
     The sshhmmggeett() system call will fail if:

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

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

     [EINVAL]           No shared memory segment is to be created, and a
                        shared memory segment exists for key, but the size of
                        the segment associated with it is less than size,
                        which is non-zero.

     [ENOENT]           IPCCREAT 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.

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

LEGACY SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>

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

     All of these include files are necessary.  The type of size has changed.

SEE ALSO
     shmat(2), shmctl(2), shmdt(2), compat(5)

BSD                             August 17, 1995                            BSD