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On Linux, you can compile in kernel support for a "Magic SysRq" key which causes SysRq to give you a menu of various debug printing and other actions. It works on serial consoles also, where instead of SysRq, a serial line break signal can map to the action (so it is completely out-of-band relative to serial data).

https://en.wikipedia.org/wiki/Magic_SysRq_key

It does on BSDs and OS X, but not on SYSV derivatives and Linux because NIH.

It generates SIGINFO on BSD. Which is even more useful and lets long running programs display progress of their choosing. E.g. how far has this big file copy come along?

On Linux, some programs (e.g. dd) actually do the same in SIGUSR1. I don't think it's possible to bind a key to sending USR1 so if you start a long dd you have to run the kill1 -USR from another shell. Or an awkward ^Z, then`kill -USR1 $(jobs -p)` then `fg`.

Not sure what sysstat on Tenex did, but you can still use ^T on the BSDs and Mac OS X to get the wait channel and some additional stats.