shmdt(2)                   DG/UX 4.30                    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)
          char *         shmaddr;

     PARAMETERS
          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 shm_ctl).

          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.




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

     shmdt(2)                   DG/UX 4.30                    shmdt(2)



     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.

     EXCEPTIONS
          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
          The related system calls:  exec(2), exit(2), fork(2),
          ipcrm(1), ipcs(1), intro(2), shmctl(2), shmget(2).

































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