[burntsushi]

Oh interesting! That is indeed quite a bit faster.

I'll have to noodle on this one. `bttf tag exec` works with arbitrary commands that can print any kind of date. But your approach require a different access pattern. I can either specialize the use case in bttf (blech) or I can figure out how to generalize your approach.

I think the key issue here is probably that it isn't line oriented. bttf composes well, but only when you have a one-to-one relationship between date and data. (Or a many-to-one is also supported, but it's many dates to one datum, not one date to many datums.) So maybe that relational model is worth figuring out how to streamline. Then I think this use case would work better.

Also, thank you! This is exactly the kind of reply I was hoping for! :D