SHMAT(2) BSD System Calls Manual SHMAT(2)

NAME
     sshhmmaatt, sshhmmddtt - map/unmap shared memory

SYNOPSIS
     ##iinncclluuddee <>

     void *
     sshhmmaatt(int shmid, const void *shmaddr, int shmflg);

     int
     sshhmmddtt(const void *shmaddr);

DESCRIPTION
     sshhmmaatt() maps the shared memory segment associated with the shared memory
     identifier shmid into the address space of the calling process. The
     address at which the segment is mapped is determined by the shmaddr
     parameter. If it is equal to 0, the system will pick an address itself.
     Otherwise, an attempt is made to map the shared memory segment at the
     address shmaddr specifies. If SHMRND is set in shmflg, the system will
     round the address down to a multiple of SHMLBA bytes (SHMLBA is defined
     in  ).  A shared memory segment can be mapped read-only by
     specifying the SHMRDONLY flag in shmflg.  sshhmmddtt() unmaps the shared mem-
     ory segment that is currently mapped at shmaddr from the calling process'
     address space.  shmaddr must be a value returned by a prior sshhmmaatt() call.
     A shared memory segment will remain existant until it is removed by a
     call to shmctl(2) with the IPCRMID command.

RETURN VALUES
     sshhmmaatt() returns the address at which the shared memory segment has been
     mapped into the calling process' address space when successful, sshhmmddtt()
     returns 0 on successful completion. Otherwise, a value of -1 is returned,
     and the global variable errno is set to indicate the error.

EERRRROORRSS
     The sshhmmaatt() system call will fail if:

     [EACCES]           The calling process has no permission to access this
                        shared memory segment.

     [EINVAL]           shmid is not a valid shared memory identifier.
                        shmaddr specifies an illegal address.

     [EMFILE]           The number of shared memory segments has reached the
                        system-wide limit.

     [ENOMEM]           There is not enough available data space for the call-
                        ing process to map the shared memory segment.

     The sshhmmddtt() system call will fail if:

     [EINVAL]           shmaddr is not the start address of a mapped shared
                        memory segment.

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

     The include files  and  are necessary for both
     functions.

SEE ALSO
     mmap(2), shmctl(2), shmget(2), compat(5)

BSD                             August 17, 1995                            BSD