shmdt(2)                       DG/UX 5.4R3.00                       shmdt(2)


NAME
       shmdt - detach a shared memory segment

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

       int  shmdt (shmaddr)
       void * shmaddr;

   where:
       shmaddr   The byte address of the attached shared memory segment to
                 be detached.  This must equal the value returned by shmat
                 when the shared segment was attached.

DESCRIPTION
       Shmdt detaches the shared memory segment located at the address
       specified by shmaddr from the calling process's data segment.

       Upon successful completion, this call changes the following fields in
       the shared memory data structure associated with the shared segment:

       shm_lpid       Changed to equal the process id of the calling
                      process.

       shm_dtime      Changed to equal the current time.

       shm_nattach    Decremented by 1.

       Detaching a shared memory segment makes it no longer available to the
       calling process.  Other users who still have the shared memory
       segment attached are not affected.  However, the calling process may
       not be able to re-attach to the segment.  This will be the case if a
       remove operation has been performed on the shared memory segment (see
       the IPC_RMID operation of shmctl).

       Calls to either exec or exit cause implicit detach operations on all
       shared segments that a process has attached.  These implicit detach
       operations change only the shm_nattach field of the shared memory
       data structure as described above for explicit detach calls.  The
       shm_lpid and shm_dtime fields remain unchanged by these implicit
       detach operations.

       Shmdt will fail and not detach the shared memory segment if an error
       occurs.

ACCESS CONTROL
       No access permission is required to detach a shared memory segment.

RETURN VALUE
       0      The detach operation was successful.

       -1     An error occurred.  errno is set to indicate the error.



Licensed material--property of copyright holder(s)                         1

shmdt(2)                       DG/UX 5.4R3.00                       shmdt(2)


DIAGNOSTICS
       Errno may be set to the following error code:

       EINVAL    Shmaddr is not the starting address of any shared memory
                 segment currently attached to the calling process.

SEE ALSO
       intro(2), exec(2), exit(2), _exit(2), fork(2), ipcrm(1), ipcs(1),
       shmctl(2), shmget(2).
















































Licensed material--property of copyright holder(s)                         2