The class identifier. To a list of the HDF5 class types please refer to the Datatype Interface API help.
But the what I could find on the Datatype Interface API at https://support.hdfgroup.org/HDF5/doc1.6/UG/11_Datatypes.html does not give a clear answer. For example, I created an attribute using H5LTset_attribute_string. I would have expected the type_class for that to be H5T_STRING but H5T_STRING (in my fortran program) has a value of 216172782113784384 but type_class was set to 3 by H5LTget_attribute_info.
The class type for a string is 3, so it looks like H5LTget_attribute_info is returning the correct value. The class types are defined in H5T_class_t in H5Tpublic.h:
@bljones
I figured out the problem. It turns out that H5T_STRING will not work under Fortran. What needs to be used is H5T_STRING_F. And if I follow the link you give to the https://portal.hdfgroup.org/display/HDF5/H5T_GET_CLASS page I do not see any mention of the fortran equivalents of the class identifiers.
This brings up another point. I find the documentation very frustrating to go through. For example, if https://support.hdfgroup.org/ is not being maintained, there should be a notice on the web pages in https://support.hdfgroup.org/ to notify and to point people where the up-to-date information is kept. [Note: There is notice on the top entry page but I found the https://support.hdfgroup.org/HDF5/doc1.6/UG/11_Datatypes.html page doing a google search so I did not see the notice on the top page.]
The problem is that while this is documented somewhere it is very easy to miss. Thus, for example, a link from the https://portal.hdfgroup.org/display/HDF5/H5T_GET_CLASS page the page where the fortran version is discussed would alleviate some frustration for someone who is new to HDF5 programming.
@bljones Thanks for the information. When I put a “print *, H5T_STRING” statement in my program I get the number 216172782113784384 and not 3. Do you understand this?