TIL the `which` command is one of those commands everyone (including me) thinks is standard simply because it's everywhere in the Unix & unixlike worlds, but which really isn't, & is nowhere in POSIX.

LWN, "Debian's which hunt," 2021-10-28: https://lwn.net/Articles/874049/

TIL the POSIX-conformant "which" is `command -v`: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html