Creating a timed launchd plist - macos

Question

I'm trying to create a plist for the LaunchAgents folder that will run perpetually and call a shell script every 30 seconds. It started with a template that I got here and that I tried to tailor to fit my needs, but it's still not working. Any help?
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>com.Intel_Watchdog</string>
<key>ProgramArguments</key>
<array>
<string>/Library/A_Intel_WATCHDOG/A_WatchDog.sh</string>
</array>
<key>StandardErrorPath</key>
<string>/dev/null</string>
<key>StandardOutPath</key>
<string>/dev/null</string>
<key>StartInterval</key>
<integer>30</integer>
<key>RunAtLoad</key>
<true/>
</dict>
</plist>
Thanks so much!

Answer 1

I dropped this in my LaunchDaemons directory, and it worked fine. So, here're some things to check:
Is the .plist getting loaded? Note that the contents of the LaunchAgents folders are loaded at login, so you either need to log out and back in, or manually load it with launchctl load ~/Library/LaunchAgents/com.Intel_Watchdog.plist (or whatever/wherever the file is). You can check its status with launchctl list.
Is /Library/A_Intel_WATCHDOG/A_WatchDog.sh executable? Check the system log (/var/log/system.log) to see if launchd is having trouble launching it.
Is the script running into trouble before it does its job? Try adding date >>/tmp/watchdog.log to it, right after the shebang, and see if anything appears in /tmp/watchdog.log. If it does, try changing the StandardErrorPath and StandardOutPath to an actual file so you can see what's going on as the script runs. Note that you'll have to unload and reload the .plist to get the change to take effect (logging out and back in would do it).
Finally, although it shouldn't cause trouble, your label doesn't follow the standard convention (unless you actually own the domain Intel_Watchdog.com). If this is for local-only use, name it something like local.Intel_Watchdog instead. If you're going to publish this item, you should base the label on a domain you own (in reverse order, with ".Intel_Watchdog" added to the end) -- see Wikipedia's entry on the reverse domain name system.