catch-all preview

Question

at the bottom of my configuration I would like to create a catch-all like preview, one for all files that contains readable text and one, below, for all other files, how can I achieve this without manually specify file extensions?

I tried with

fileviewer <text/plain> mycommand
fileviewer * mycommand

but I'm missing something in the logic.

Answer 1

Looks correct to me, although you may want to change <text/plain> to <text/*>. It's also possible that some application-specific mime types need to be listed, you can look those up in Ctrl+G dialog when a file isn't previewed as you expect.