because most of the coreutil functionality is already availible in libraries of most languages. Article mentions that there are crates for the logic. The hard part is command line parsing and output formatting, and your library should have neither of those.

I've seen plenty of shell scripts rewritten in Python because they grew too big, and most of the time coreutil commands just get replaced with standard library calls. There are exceptions (like sorting files which do not fit in memory) but otherwise standard library is good enough