Trap Computer Shutdown Signal

[Penguin Guy]

Hi! I've got a shell script that downloads and displays a sunmap as the background every 60 seconds. The program reverts the background to the original when it ends by using a trap statement - everything works fine apart from when the script is ended by a computer shutdown, in which case the background is not reverted. This is part of a small Launchpad project and this issue is putting on hold a merge, so any help would be greatly appreciated.

View File - Download File - View Bug

Thanks!


SOLVED
Turns out trap doesn't work with loops, use the wait statement to fix this.

[trent.josephsen]

I must be misunderstanding you. If you're about to shut down the computer, why do you care whether it gets reverted or not?

[Penguin Guy]

If you're about to shut down the computer, why do you care whether it gets reverted or not?

Because when you next start the computer you'll have no wallpaper.

[trent.josephsen]

Because when you next start the computer you'll have no wallpaper.

Oh! I set my wallpaper in .xinitrc, so that never even occurred to me.

Maybe SIGKILL? But I would have expected SIGTERM to work.

[Penguin Guy]

Maybe SIGKILL? But I would have expected SIGTERM to work.

I'm pretty sure you can't trap SIGKILL, but I'll give it a go anyway.

EDIT: Nope, that doesn't work either.

[PaulM1985]

From searching the net it seems that SIGTERM should work.

However if it doesn't when the system shuts down rc.d scripts are called and maybe you could add something in there to notify your program.

Below is the link I plagiarised this information from

http://stackoverflow.com/questions/2...tdown-on-linux

Hope it is of some help.

Paul

[Penguin Guy]

From searching the net it seems that SIGTERM should work.

However if it doesn't when the system shuts down rc.d scripts are called and maybe you could add something in there to notify your program.

Below is the link I plagiarised this information from

http://stackoverflow.com/questions/2...tdown-on-linux

Hope it is of some help.

Paul

I'm already using SIGTERM, and rc.d scripts are really a bit advanced for this program. Are there any other possible suggestions?

[trent.josephsen]

I'm pretty sure you can't trap SIGKILL, but I'll give it a go anyway.

No, of course not. I meant that perhaps your script is being sent KILL instead of TERM, even though TERM should end the script. Sorry for miscommunicating.

[Penguin Guy]

I meant that perhaps your script is being sent KILL instead of TERM, even though TERM should end the script.

Looks like it is, but why?

[ov3rcl0ck]

Shell scripts are too high level to catch SIGTERM or SIGKILL. Maybe theres a way to do it, but I don't think trapping a signal will do it, seeing as the signal is sent to BASH/shell rather than your script. Unless BASH will relay this information to a shell script, which I don't think it does.