SIGINFO
Ctrl+T on the BSDs and macOS: it tells you what the process is doing, interrupting nothing.
The family's polite question: on the BSDs and macOS, Ctrl+T rings SIGINFO at the foreground process, which answers with a status line — without stopping, without dying. The kernel itself prints load and state; programs like dd and ping add their progress.
Linux never hung this bell in its tower: there, the name SIGINFO is merely a synonym for SIGPWR on some architectures, and the habit went to dd's USR1 — or to status=progress. Anyone migrating from macOS misses the ring.
$ ping stickybit.com.br (on macOS)
^T
load: 2.05 cmd: ping 24966 running 0.00u 0.00s
2/2 packets received (100.0%) 12.986 ms