Launchd is an Apple construct designed to replace the various methods of launching daemons in Unix: cron, init.d, inetd, etc., including triggers based on the filesystem. It was first included in Mac OS X 10.4, “Tiger.”

Resources

• launchd’s creator, Dave Zarzycki, talks about launchd at Google. He discusses the circumstances that lead to launchd’s creation, the problems it solves, and goes into some depth on how it works and how to use it. He also discusses some changes to launchd coming in Mac OS X 10.5.
• launchd in depth from AFP548
• All about launchd items from MacGeekery
• Some launchd recipies, also from MacGeekery, shows some scenarios for using launchd.
• Apple’s Developer’s Connection has some tips on getting started with launchd.
• Bug reports, SubVersioN trees, and more at the official macosforge page.