TIL ... many things. But perhaps most surprising, to me:

$ which "["
/usr/bin/[

I always thought

[ ... ]

was the

sh

builtin and

[[ ... ]]

the bash more advanced version of that builtin and

test

the system utility (

/usr/bin

) equivalent of the

sh

[ ... ]

builtin. But: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html

To clarify, your surprise was that

[

wasn't a builtin, right? Everything else was still on point from what I can tell.

Most directly I was surprised to see

[

was a binary on the PATH on my machine. It is not the same binary as

test

and it behaves differently. You must pass it a last argument of

]

or it errors saying that and it accepts

--help

which

test

does not (on my machine). Everything else was coming to grips with that.