i want to make a program run when a person types 'finger USERNAME', username being my username. how can i do this?

Please don't try this. It can cause problems. The way it was done was to make .plan a named pipe and leave a program running that was writing to the pipe. The program would notice when a reader to the pipe existed and would start to run.

But if that program died, fingers would just block. If they were remote fingers resources would lock up until the system crashed. This was considered to be a denial of service attack. Most finger programs now will stat .plan and ignore it if it's not a plain file. So you probably can't do this anymore.

Here is a story that you probably won't believe...I know it's true and I can hardly believe it...

In my youth, I once decided to have a little fun with .plan. I set it to "Bus error(coredump)". I thought this was funny, but since I was the sysadm and people only fingered me to get my phone number, they just reported it to me as a bug. So I upped the ante to "Trolleycar error (core ejected) Deleting all files in current directory...exporting this behavior to all reachable networks!". I felt certain that folks could figure out that this message was bogus... Then I got a call from a guy who said his officemate had just got that message and was racing to the computer room to yank all of the cables out of the system. I stopped him before he did any damage. Then I deleted my .plan and haven't had one since.

kill -l | grep TRLY

22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGTRLYCR


See??? They were right to be upset!!!

I have seen people rename core files to .plan though... horrible mess on some terminals. Can really snag up some low-bandwidth links too.