GoKawiilBlog post traces history of cp -r vs -R flag divergence
A developer blog post examines whether the cp command's -r and -R recursive-copy flags have ever behaved differently. It traces GNU coreutils source code back to 1992, finding the two flags originally set different internal variables, before being merged into identical behavior in 2002. The post also checks OpenBSD 7.9 and NetBSD 11, finding both still treat -r and -R as distinct, with manuals recommending -R.