kill: For one simple reason

I kept back the kill command from coreutils because there’s one thing it can do, one flag in particular, that I felt I should mention. kill itself has a lot of options for stopping programs — gracefully or ungracefully — but the most helpful thing it does for me is this:

kill -USR1 9003

where 9003 (or whatever) is the PID of my old friend dd, the cool tool with no output whatsoever. Except that when it gets a -USR1 flag from kill, it actually spits out a little information.

kmandla@6m47421: ~$ dd if=/dev/zero of=/dev/null
9482411+0 records in
9482411+0 records out
4854994432 bytes (4.9 GB) copied, 12.4079 s, 391 MB/s

So in a worst-case scenario, when I’m wondering if dd is actually still running or has fallen into a trance state and maybe never coming back, kill and the -USR1 flag at least tells me if it has a pulse.

I know kill does other stuff too, but I do enjoy the irony of sending the kill command to see if a program is still alive.