n or 0             Upon successful completion, the value returned
                       by the function depends on cmd as follows:

                       o  GETVAL - The value of semval

                       o  GETPID - The value of sempid

                       o  GETNCNT - The value of semncnt

                       o  GETZCNT - The value of semzcnt

                       o  All others - 0

    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EACCES - Operation permission is denied to
                          the calling process.

                       o  EFAULT - The arguments passed to the
                          function are not accessible.

                       o  EINVAL - The value of semid is not a valid
                          semaphore identifier, or the value of
                          semnum is less than zero or greater than
                          or equal to sem_nsems, or the value of cmd
                          is not a valid command.

                       o  EPERM - The argument cmd is equal to IPC_
                          RMID or IPC_SET and the effective user ID
                          of the calling process is not equal to that
                          of a process with appropriate privileges
                          and it is not equal to the value of sem_
                          perm.cuid or sem_perm.uid in the data
                          structure associated with semid.

                       o  EVMSERR - OpenVMS specific nontranslatable
                          error code.