Using DynDNS for iPhone OS 3.0 without crontab but with launchd

Apple iPhone OS 3.0 does not have crontab anymore. You are supposed to use launchd's facilities to execute something at a scheduled interval. Here is an example of a simple script to update the IP-address at DynDNS.org.

The script /var/mobile/update-dyndns.org contains:

#!/bin/sh

host="your-host-name.dyndns.org"
user="your-username"
pass="your-password"

oldip=$(cat /tmp/ip)
wget -o /dev/null -O - http://ip.serverchief.com/ > /tmp/ip
ip=$(cat /tmp/ip)

if [ "$oldip" != "$ip" ] ; then
 echo -n "$(date) "
 echo $(/usr/local/bin/wget -O - "http://$user:$pass@members.dyndns.org/nic/update?hostname=$host&wildcard=NOCHG&bacakmx=NOCHG"  2> /dev/null)
fi

The file /var/LaunchDaemons/org.dyndns.update.plist contains:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>  
	<key>Label</key>
	<string>org.dyndns.update</string>
	<key>ProgramArguments</key>
	<array> 
		<string>~/mobile/dyndns-update.sh</string>
	</array>
	<key>StartCalendarInterval</key>
	<dict>  
		<key>Minute</key>
		<integer>3</integer>
	</dict>
</dict>
</plist>

And execute:

# launchctl load org.dyndns.update.plist

Now your IP will be update every 3-rd minute. Have fun!

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Comments

Thu, 02/11/2010 - 23:03 — Philip C (not verified)

Instead of running the script

Instead of running the script every three minutes when nothing has changed, why not use the WatchPaths key and only run on wake/sleep or a network state change:

	<key>WatchPaths</key>
	<array>
		<string>/Library/Preferences/SystemConfiguration</string>
	</array>

Thu, 07/08/2010 - 04:20 — bac (not verified)

So, does this work?

So, does this work? (WatchPaths instead of every 3 min?)

In my country you pay by traffic so if the connection could be avoided it would be better (plus you'd be saving battery life!)

Mon, 01/11/2010 - 15:05 — Anonymous (not verified)

So does this fail silently

So does this fail silently when there is no internet connection? i have an itouch that inst always connected to wireless, but i would like to set it up to interface with dyndns

Thu, 01/07/2010 - 21:07 — Anonymous (not verified)

Hi there.. I was wondering

Hi there..

I was wondering where requests for ip.serverchief.com come from, i get 100+ unique hits per day.. now it makes sense :)
I thought no-one will use this except me..

glad its being put to a good use. i will keep this portion up.

Regards
ServerChief

www.serverchief.com

Sun, 12/20/2009 - 00:06 — Carlo (not verified)

From Apple's documentation

From Apple's documentation I'd have taken that "StartCalendarInterval Minute 3 "
causes launchd to start the program at 01:03 a.m., 02:03 a.m. and so on, and that one would have to put it like "StartInterval 3" for executing the script every three minutes. Unfortunately up to now neither way would run on my iphone, so I can't just try and tell. What's your actual experience: does the script execute every three minutes with the script given?

Thanks
Carlo

Fri, 09/25/2009 - 20:21 — Dan (not verified)

thanks, stephan.

Me in IT UNIX/Linux consultancy