[launchd-dev] launchctl - LAUNCHD_SOCKET

[Eric Long]

Hi,

I have a daemon and one of its tasks is to check for launchd jobs in user
LaunchAgents folders, see if they failed to execute because the machine was
off, or whatever, and start the jobs that were missed.  These jobs are all
directly related to a feature in our software.

The daemon runs in the global root context.  When it performs checks it
iterates jobs for all logged in users.

To start a job, I use NSTask to launch launchctl.

If I fail to set the euid to the user whose job I want to start, I get an
error saying no such process, or something to that effect.  When I set the
euid before launching the task, I get back an error saying I must be the
root user to conduct the operation and also a socket not connected error
message.

Looking at the man page for launchctl I see an environment variable named
LAUNCHD_SOCKET. My guess is that even though I'm launching the task while
the euid is set to the correct user, its still not executing in the user
context.  I'd attempt to set the LAUNCHD_SOCKET path, but I don't know what
the path should point to.  Looking at the docs, I see:

> Each instance of launchd has a directory in /var/launchd, identified by the
> uid or by the uid followed by a pid number, containing a socket for
> communicating with it. The environment variable LAUNCHD_SOCKET, when set to
> the full path of one of these socket files, specifies a specific instance of
> launchd to communicate with.

I see directories for users, but the directories are empty.

What is the proper way to start the missed job for a given user from my
daemon?


Thanks,


Eric