Signature:

      SUBROUTINE h5oopen_by_idx_f(loc_id, group_name, index_type, order, n, &
           obj_id, hdferr, lapl_id)
        IMPLICIT NONE
        INTEGER(HID_T)  , INTENT(IN)            :: loc_id
        CHARACTER(LEN=*), INTENT(IN)            :: group_name
        INTEGER         , INTENT(IN)            :: index_type
        INTEGER         , INTENT(IN)            :: order
        INTEGER(HSIZE_T), INTENT(IN)            :: n
        INTEGER(HID_T)  , INTENT(OUT)           :: obj_id
        INTEGER         , INTENT(OUT)           :: hdferr
        INTEGER(HID_T)  , INTENT(IN) , OPTIONAL :: lapl_id

Inputs:

      loc_id      - A file or group identifier.
      group_name  - Name of group, relative to loc_id, in which object is located.
      index_type  - Type of index by which objects are ordered.
      order       - Order of iteration within index, NOTE: zero-based.
      n           - Object to open.

Outputs:

      obj_id      - An object identifier for the opened object.
      hdferr      - Returns 0 if successful and -1 if fails.

Optional parameters:

      lapl_id     - Link access property list.