#include <tkrzw_dbm_hash.h>
#include <tkrzw_dbm_shard.h>

...

// tkrzw::HashDBM dbm;
// dbm.Open("/dev/shm/casket.tkh", true).OrDie();

   tkrzw::ShardDBM dbm;

   const std::map<std::string, std::string> params = {
     {"num_shards", "8"}, {"dbm", "HashDBM"} };

   dbm.OpenAdvanced("/dev/shm/casket.tkh", true, tkrzw::File::OPEN_DEFAULT, params);

   for (int i = 0; i < nfiles; ++i)
      get_properties(fname[i], nthds, dbm);

   dbm.Close();