UNIX for Dummies Questions & Answers

I was talking to a coworker and we got into a discussion about the -9. No one knew where the -9 came from and it's not in the man. I suggested that it was like counting to 10 (0-9) and you finally get to the point that that's it, the durned thing is going to die. So how did the -9 come to mean "NOW!" without reservation? It looks like it has the same impact as -KILL or -s KILL. But how did the -9 become that?

It's a coincidence. The numbers have no particular voodoo meaning, different signals were assigned numbers purely arbitrarily as they were invented. Not all the same numbers everywhere either; -9 is a very old signal (and probably defined as KILL in some standard or other now) but many others aren't so strictly defined, and may vary between different UNIX implementations. Some don't have USR1 for instance.

On my system at least you can see a fairly comprehensive list of signals in 'man kill'.

Thanks for the info. Your man page is seriously more detailed than ours.

I didn't think it was voodoo. We just began making up things for why they used the 9. Got silly. I was hoping for a good story. Ah, well. The guys'll be disappointed.