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copied!<p>Oh how <code>launchd</code> drives me crazy.... </p> <p>To cut to the chase, after much study and experimentation, this is how I do it on 10.5+:</p> <pre><code># If possible, tell launchd to start the LaunchAgent. This will fail on 10.4. # $F[0] is the pid # $F[1] is the username # $F[2] is the first word of the command ps -ww -A -opid,user,command | \ perl -nae 'if($F[2] =~ /\bloginwindow\b/) { system( qq(launchctl bsexec $F[0] su $F[1] -c "launchctl load -w <your_plist>")) }' </code></pre> <p>I have found no way to achieve this directly on 10.4. I cheat on 10.4 and just run the thing the LaunchAgent would have run, even though it has a GUI and you're not supposed to be able to do that (you can anyway in 10.4-10.6; you can't in 10.7). On 10.4, the LaunchAgent works correct after the next reboot.</p> <p>The above code looks for <code>loginwindow</code> processes and uses <code>bsexec</code> to run commands in those contexts. Keep in mind that with Fast User Switching, there can be multiple contexts.</p> <p>Some useful links:</p> <ul> <li><a href="http://developer.apple.com/library/mac/#documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/Introduction.html" rel="nofollow noreferrer">Daemons and Services Programming Guide</a>. You have to read it, but it won't actually answer any of the hard questions. But it will at least give you hints at where everything is located.</li> <li><a href="http://developer.apple.com/library/mac/#technotes/tn2083/_index.html" rel="nofollow noreferrer">TN2083</a>. This is a maddening document that raises as many questions as it answers, but is gospel and mandatory reading for anyone entering the abyss of <code>launchd</code>.</li> <li><a href="https://stackoverflow.com/questions/1106638/starting-stopping-a-launchd-agent-for-all-users-with-gui-sessions">Starting/stopping a launchd agent for all users with GUI sessions</a>. This has several other useful links and explanation.</li> </ul> <p>IMO, <code>launchd</code> is one of the worst "great ideas" Apple has ever deployed. The idea is very useful, but the API is horrible.</p>

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