ls -r actually lists entries in reverse order! It needs -R as well.

cp and rm accept either.

Looking at some man pages the only commands I found where -R didn’t work were scp and gzip where it doesn’t do anything, and rsync where it’s “use relative path names”.

(Caveat: BSD utils might be different, who knows what those devils get up to!)

Not chmod related, but I’ve made some other interesting mistakes lately.

Was trying to speed up the boot process on my ancient laptop by changing the startup services. Somehow ended up with nologin never being unset, which means that regular users aren’t allowed to log in; and since I hadn’t set a root password, no one could log in!

Installed a different version of Python for a project, accidentally removed the wrong version of Python at the end of the day. When I started the computer the next day, all sorts of interesting things were broken!

Aha! I didn’t get that you meant the issue was accidentally using -r instead of -R since both you and OP wrote the upper case one.

I’m a lot more used to -R so I instead get caught off by commands where that means something other than recursive :)

I mostly use symbolic mode and honestly don’t get why everyone else seems to use octal all the time.

That’s what -R does in chmod as well? I feel like something here is going completely over my head. Or are you-all using another version of chmod?