Example of writing and reading file with HDF5 in C. Based on https://scivision.co/linking-libhdf5-dev-with-cmake/

myprog.c

#include "hdf5.h"
#define FILE "dset.h5"

int main() {

   hid_t       file_id, dataset_id,dataspace_id; /* identifiers */
   herr_t      status;
   int         i, j, dset_data[4][6], read_data[4][6];
  hsize_t     dims[2];

   /* Initialize the dataset. */
   for (i = 0; i < 4; i++)
      for (j = 0; j < 6; j++)
         dset_data[i][j] = i * 6 + j + 1;

   /* Create a new file using default properties. */
   file_id = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

   /* Create the data space for the dataset. */
   dims[0] = 4; 
   dims[1] = 6; 
   dataspace_id = H5Screate_simple(2, dims, NULL);

   /* Create the dataset. */
   dataset_id = H5Dcreate2(file_id, "/dset", H5T_STD_I32BE, dataspace_id, 
                          H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);

   /* Write the dataset. */
   status = H5Dwrite(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, 
                     dset_data);

   /* End access to the dataset and release resources used by it. */
   status = H5Dclose(dataset_id);

//------------------------------------------------------

   /* Open an existing dataset. */
   dataset_id = H5Dopen2(file_id, "/dset", H5P_DEFAULT);


   status = H5Dread(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, 
                    read_data);

   for (i = 0; i < 4; i++)
      for (j = 0; j < 6; j++)
        printf("%d ",read_data[i][j]); // 1-24

   /* Close the dataset. */
   status = H5Dclose(dataset_id);

   /* Close the file. */
   status = H5Fclose(file_id);
}