I have some old OS 9 fonts which contain the font data in the resource fork. When I try to link such a font in a @font-face and open up the HTML in a browser, the text still
Since this is one of the first search results when searching how to handle Resource fork fonts on modern macOS systems here is a solution for batch converting a large group of font suitcases.
First we can group them all in a single directory taking advantage of the find command, because find doesn't see the resource fork and consider the file empty, we create a new directory in the user home and copy all the suitcases there:
mkdir ~/rsrc
find . -type f -empty -exec cp {} ~/rsrc/ \;
Then in mac we can use brew to install Fondu
brew install fondu
Finally we move to the directory with all the suitcases and run fondu on each file like this, the secret to get fondu to work is to make it read the resource fork by adding /../namedfork/rsrc at the end of the file, otherwise it fails.
cd ~/rsrc
find . -type f -empty -exec fondu -force {}/..namedfork/rsrc \;
When the command finishes you should have a folder with the new .ttf, .bdf and .pfb files.
You can delete the suitcase files from this directory running:
find . -type f -empty -delete