n                  Successful completion. The function returns a
                       non-negative integer semaphore identifier.
    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EACCES - A semaphore identifier exists for
                          key, but operation permission as specified
                          by the low-order 9 bits of semflg was not
                          granted.

                       o  EEXIST - A semaphore identifier exists
                          for key but ((semflg &IPC_CREAT) &&(semflg
                          &IPC_EXCL)) is nonzero.

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

                       o  EINVAL - The value of nsems is either
                          less than or equal to 0 or greater than
                          the system-imposed limit, or a semaphore
                          identifier exists for key, but the number
                          of semaphores in the set associated with it
                          is less than nsems and nsems is not equal
                          to 0.

                       o  ENOENT - A semaphore identifier does not
                          exist for key and (semflg &IPC_CREAT) is
                          equal to 0.

                       o  ENOSPC - A semaphore identifier is to be
                          created but the system-imposed limit on
                          the maximum number of allowed semaphores
                          system-wide will be exceeded.

                       o  EVMSERR - OpenVMS specific nontranslatable
                          error code.