TIL about `pv --watchfd`

Useful if you forget to use pv at all, or, recently, when I ran pv and didn't notice for probably 10-20% of the file that the progress bar was missing. Previously, I've resorted to tricks like

mkfifo pipe pv ... > pipe <pipe restofcommand 

in separate terminals, so that I'd get a useful pv progress bar.

But since the pipeline was this far along, I thought I'd look up that pv --remote option, and found pv --watchfd instead. Should be able to watch anything doing big sequential file reads, not just pv itself!