Well, it’s not pretty yet, but I’ve got a very basic GUI version of dusage going:
https://movq.de/v/9b1c7016f6/MVI_7449.MOV.mp4
To me, it’s just super cool that I’m able to write programs for OS/2. 😎 That operating system will always hold a special place in my heart, I guess. It ran on my Model 80 back then (and maybe even the Model 30, but I’m not 100% sure anymore) and thus a lot of my earliest memories about using computers are OS/2 related. (And DOS related, of course. I had a dual boot setup on the Model 80, believe it or not …)
Anyway, writing that little program got much easier after I’ve found this page which contains a lot of valuable information:
https://komh.github.io/os2books/
This is a collection of OS/2 books by a person who’s apparently quite active in the realms of ArcaOS (one of OS/2’s “descendants”).