When linux commands list their usage, this usually is how they do it (for eg wget):
wget [option]... [URL]...
From what I understand of this pattern of specifying command usage, this is not the usual regex way of specifying patterns and for the wget command says that it is not mandatory to specify any options and by that logic it is not mandatory to specify any URL as well. I mean I can directly do
and this will work. So the options are not mandatory. If the options are not mandatory because they are in square brackets, then following through with that logic specifying a URL should not be mandatory as well and just
as a command should work as well. My question is- Is there some document where this pattern of specifying command usage is elaborated on?