I have a file on my Mac of a slightly unusual type. Let's say it's an "XYZ" file. Maybe I downloaded it from somewhere. I don't have any programs on my Mac that know about XYZ files, so if I view it in Finder is is shown with a plain icon and a generic description e.g. "Document". If I check its type, it seems that macOS has allocated it a "dyn.*" UTI:
% mdls -name kMDItemContentType ~/foo.xyz
kMDItemContentType = "dyn.ah62d4rv4ge81u8p4"
I do have an app on my iPad that knows about XYZ files. The app has a UTImportedTypeDeclarations entry for .xyz in its Info.plist. I transfer the file to my iPad using AirDrop. Annoyingly, the iPad does not offer to open the file with the appropriate app.
It seems to me that the iPad has blindly trusted the dyn.* UTI that macOS allocated for the file, and which presumably has been sent by AirDrop. It has not used the filename extension mapping from its app's Info.plist to determine that the file is an XYZ file. That may be considered a bug in iOS but that's not my question...
My question is: is there anything that I can do on my Mac to tell it that this file foo.xyz is of type UTI com.example.xyz ?
I was expecting to find either an md... command to modify the metadata, including the UTI, for a file, or some way to do this by setting an extended attribute. I have not yet found either. Any ideas anyone?