What the heck is Apple_Ubiquity_Message?
environment-variables, icloud, launchctl, macos, operating-system
Solution
It's part of Apple's ubiquity system (more commonly known as iCloud). Programs that support iCloud can use it to communicate with the ubiquity daemon (`ubd`), and it's defined in your environment so programs that use iCloud can find & use it.
More technically: the file /System/Library/LaunchAgents/com.apple.ubd.plist tells your user instance of `launchd` to create that socket file, and then put a reference to it in the environment of all processes `launchd` creates under the name Apple_Ubiquity_Message. launchd doesn't actually start `ubd` until something connects to & uses that socket. I'm not particularly familiar with the iCloud APIs, but I don't think app developers access it directly; instead they use iCloud APIs and those use Apple_Ubiquity_Message behind the scenes.
Net result: you can ignore it, unless you're interested in the details of how iCloud works.
UPDATE: Apple apparently changed the way this works in Mavericks -- `ubd` is still there, but Apple_Ubiquity_Message (and the socket it pointed to) are not. I'm not sure what the new method to communicate with `ubd` is (maybe Mach messages?), but any program that uses the iCloud APIs should just continue to work.
Problem
OSX 10.8.4 ``` > printenv ... Apple_Ubiquity_Message=/tmp/launch-YzDhDA/Apple_Ubiquity_Message ... > ls -al /tmp/launch-YzDhDA/Apple_Ubiquity_Message srw-rw-rw- 1 user wheel 0 Jul 25 10:01 /tmp/launch-YzDhDA/Apple_Ubiquity_Message ``` StackOverflow wants me to add some sentences with proper grammar. I tried to cat that file, but it does not emit anything as far as I can tell.