man -k open should surface lsof on your system. On mine it only has the description 'open files', though, which might not be obviously relevant to many people.

man -k open should surface lsof on your system. On mine it only has the description 'open files', though, which might not be obviously relevant to many people. I'm not sure what macOS or FreeBSD `man` have, but GNU `man` has `-K` as well as `-k`. The uppercase version searches the manpages globally, instead of just their short descriptions. So something like man -K -a 8 "list open" port will turn up `lsof` on GNU, even if `apropos` doesn't. If you have a tldr client installed, that can also be useful for searching through common examples including for programs you may not have installed. For example with tealdeer, the following (Fish) surfaces both lsof and netstat as options: for page in (tldr -l) tldr $page | rg -A2 -i '\b(find|list)\b.*\bport' end and for page in (tldr -l) tldr $page | rg -A2 -i '\bkill\b.*\bport' end shows that fuser and fkill can both do the same thing as killport. Grep sucks as a search interface for tldr, though, so you probably want a better tldr client than I have, which will do global search, or an FZF script that will let you filter through tldr results. Discovering new (to you) tools which are not yet installed is a good reason to use the web to look up Unix stuff, especially after you've checked the manpages and your package manager.