Return_Values

   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.