Failed to add Group to h5 file via H5G.create

%%1st step: create a h5 file and close it

fn = 'D:\QMDownload\3\example.h5';
fid = H5F.create(fn);
gid = H5G.open(fid,'/');
plist = 'H5P_DEFAULT';
gid1 = H5G.create(gid,'group1',plist,plist,plist); 
gid2 = H5G.create(gid1,'group11',plist,plist,plist);
gid3 = H5G.create(gid2,'group111',plist,plist,plist);
H5G.close(gid);
H5G.close(gid1);
H5G.close(gid2);
H5G.close(gid3);
H5F.close(fid);
h5disp(fn)

% now add another group
fid = H5F.open(fn);
gid = H5G.open(fid,'/group1');
plist = 'H5P_DEFAULT';
gid1 = H5G.create(gid,'group12',plist,plist,plist);

Error appears:

Error using hdf5lib2
The HDF5 library encountered an error and produced the following stack trace information:

      H5G__obj_create_real    no write intent on file
      H5G__obj_create         unable to create group
      H5G__create             unable to create group object header
      H5O_group_create        unable to create group
      H5O_obj_create          unable to open object
      H5L_link_cb             unable to create object
      H5G_traverse_real       traversal operator failed
      H5G_traverse            internal path traversal failed
      H5L_create_real         can't insert link
      H5L_link_object         unable to create new link to object
      H5G__create_named       unable to create and link to group
      H5Gcreate2              unable to create group

Error in H5G.create (line 27)
group_id = H5ML.hdf5lib2('H5Gcreate', varargin{:});

Answer 1

[Jeremiah Hess]

Hey! It's been a while since this question was asked, but I encountered the same problem and managed to figure out the solution, so I'm posting it here to help any future members.

The simple explanation for the error is that the low-level function H5F.open defaults to opening the file in read-only mode, making it impossible to create new groups or datasets in the file. A simple look at the H5F.open documentation yields the following solution:

% now add another group
plist = 'H5P_DEFAULT';
fid = H5F.open(fn,'H5F_ACC_RDWR',plist); % Opens the file in read-write mode
gid = H5G.open(fid,'/group1');
gid1 = H5G.create(gid,'group12',plist,plist,plist);