Run a shell script at login?

Question

I would like to run a simple shell script each time a user logs in. Currently, I have it wrapped in an Automator executable that is included in "Login Items", but figured there must be a more elegant way? Thanks.
More info:
The problem I'm trying to solve is that of file permissions when sharing one iTunes and one iPhoto library between multiple users on one computer. The libraries are located in /Users/Shared and the apps were pointed to the relocated libraries by holding down 'Option' on startup. The problem is that work done by each user in the iTunes or iPhoto library inherits the default permission settings of that user, making any new additions to the libraries, read-only to the other users. I'm using `chmod` on login to fix it. Let me know if you know of a better way to address this. Thanks again.

Answer 1

I wrote a simple shell script that executes each time a user logs in (well, actually, each time I log in, coz' it's not really applicable to other users). It syncs my work and home addressbooks and iCal calendars to one another.
I named it "sync". Then I read somewhere that if you wanted to make it double-clickable (to launch it from the Finder), I appended a ".command" filename extension (so it's now named "sync.command"). I also did a chmod 755 to that file so that it had execute privileges. Depending on whether you give each user their own copy of this thing, or keep a single copy in, say, the /Users/Shared directory, you may have to play around with chmod. Whatever, just so long as the user that has just logged in has execute permissions to the file, and to the entire path to the file, you should be good.
Then, in SysPrefs > Accounts > Login Items, I added that "sync.command" file to the list. So, really the only difference is I'm not wrapping mine inside an Automator script like you are.
I had tried adding it to ~/Library/LaunchAgents and make a launchd plist for it, that would kick it off at login. But I didn't get that to work. Don't know why. But just adding the double-clickable executable unix script to the Login Items list did the trick. Whether the plist has to hang out there with it, I don't know. I still have it there, though, in case I ever get motivated to figure out what's wrong with my launchd plist file. So, if just adding it to the Login Items list doesn't do it for you, you could try making a (functional?) launchd plist for it and plopping them both in ~/Library/LaunchAgents, too. That's how I am now, and, like I said, it launches at user login as that user's process (not as a root process like the above referenced article said how login hooks worked -- although, you may want it to run as root since you want this to work with multiple users...in which case, you might want to listen to Cole and not me...).