It helps that for most cli tools, any incorrect usage will show the usage text, including --help

> Discoverability in CLI is --help.

Unless it’s one of those programs that are like “unrecognized option --help, use -h to see help”.

If --help even lists everything. man [whatever] might contain more options. And both may leave out critical information.

You also have to just know what program to invoke with the —help arg.

Good luck guessing ‘grep’ from first principles.

Man -k is often good for this