Most of us will be familiar with the common watch -n5 "killall -USR1 dd" trick when doing a huge byte transfer using DD on Linux to check it’s progress.
OSX is different (well, 10.10 is, ymmv with other releases), because why the hell not, and instead of the -USR1 signal, opts for the -SIGINFO signal. Sure, this might make more sense to the uninitiated, but to those of us who have the -USR1 flag imprinted on our brains, it’s rather painful to find that calling killall -USR1 dd actually kills the DD process.
That, of course, is without mentioning that OSX doesn’t ship with watch out of the box, either.