launchd
launchd
- Subject: launchd
- From: Adam Bell <email@hidden>
- Date: Tue, 15 Aug 2006 11:07:00 -0300
Title: launchd
I've been 'playing' with launchd (Tiger's upgrade of CRON) after
reading the cover article in MacScripter.net. launchd runs user
daemons that are created from a plist located in
~/Library/LaunchAgents/. These are, in turn, launched by launchctl.
Among launchd's plist keys (see man launchd.plist - a not at all
obvious place to look) are these two:
StartInterval<integer>
This optional key causes the job to be started every N seconds. If the
system is asleep, the job will be started
the next time the computer wakes up. If
multiple intervals transpire before the computer is woken, those
events will be coalesced into one event upon wakefrom
sleep.
WatchPaths <array of
strings>
This optional key causes the job to be
started if anyone of the listed paths are modified.
I'm not sure if those options make sense
together.
Clearly, the first of these is an analog of
a stay-open 'on idle' application included in the user's Account/Login
Items, and the second is reminiscent of a Folder Action, except that
it can also point to a file. I haven't yet tested the extent of its
capacity to recognize that a file has been 'modified'. Does this
include size or modification date?
Does anyone know if AppleScript v 1.10.7
actually uses launchd daemons for 'on idle' and 'Folder Actions' or
are the launchd versions actually a more powerful and basic
alternative? Launchd plists are relatively straight-forward to
construct and launch with do shell script commands (with no permission
issues since they're in the user's Library folder) so this is an
interesting alternative that is possibly more robust than Folder
Actions, for example, and is invisible to the user, unlike a normal
'on idle' handler's application. Interesting possibilities abound, and
I'd be interested to hear what others are using launchd + AppleScript
for.
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