[launchd-dev] Programmatic interface to launchctl and some other questions, OS X 10.5

[Jerry Krinock]

On 2010 Oct 25, at 18:01, eveningnick eveningnick wrote:

> As i understand, when a user
> doubleclicks my Cocoa application's bundle, the application is
> launched with non-root privileges, which means i can't "launchctl
> load" my agent into /Library/LaunchAgents - i can only do that with
> /Users/username/Library/LaunchAgents directory.

That is correct.

> Also there's a /usr/include/launch.h file, which provides some kind of
> API, but i've no idea how to use it, and i am not sure if it gives any
> means to load/start/stop/unload agents. Maybe i could use it somehow?

Anyone know what he's talking about?

> Most suggestions about programmatical management of agents are about
> calling "[NSTask launchProcess:@"launchctl {operation} {label}"]". If
> there is no other better choice, i'd take it

That's how I do it.  It is sad, and a chore.

> but i am a little
> confused about privileges - i won't be able to install an agent to
> /Library/LaunchAgents, will I?.

That is correct.  You'd have to write a Privileged Helper Tool based on Better Authorization Sample to do that, which is a *really* big chore.  You might find it a little easier if you use my framework…

    http://sheepsystems.com/sourceCode/authTasksCocoa.html

> I'm sorry if i'm saying nonsense, but if i call "[NSTask
> launchProcess:@"sudo launchctl {operation} {label}"]" will it count as
> a launch from root, or this trick works only if its done in a
> terminal?

Nice try :)  But that sudo won't work because there is no UI for the user to type in their credential.  Sorry, you need a Privileged Helper Tool.

> how can i determine, if my agent is running or not, from my Cocoa
> application? and how could i determine if it's registered (loaded, in
> terms of launchctl) or not? Calling [NSTask launchProcess:@"launchctl
> list | grep com.mycompany.myagent"] and then parsing the returned
> string seems wrong to me :/. Is it really the only choice?

That's the only choice that I know of.  Again, this is quite sad.

> I was also searching for the info on how to launch a process, that is
> a console one (Gui-less). Most suggestions are about using launchd
> instead of fork/exec-ing it. How is it done usually?

Well, yes.  But launchd is *normally* used in this way, to launch gui-less tools.  The path to your tool is the first element in the ProgramArguments array.  If you wanted to launch an *app* with launchd, you'd need to use /usr/bin/open.

> Should i
> necessarily create and save that *.plist to the
> /Users/username/Library/LaunchAgents/ directory and then call that
> "[NSTask launchProcess:@"sudo launchctl {operation} {label}"]"?, first
> with "launchctl load" and second with "launchctl start"?

Yes, but again, that sudo ain't going to work, but if you are launching an agent from ~/Library/LaunchAgents, you don't need sudo.  Also, I use "launchctl load" but   I've never even heard of "launchctl start".  Sounds like it might be the same as putting RunAtLoad into the plist?  That's what I do.

You should appreciate that to use system-domain agents (/Library/LaunchAgents) instead of user-domain agents (~/Library/LaunchAgents), you are entering the realm of security and privileges, and greatly complicating your life.  However, if you really need to do this, address questions in these areas to apple-cdsa at lists.apple.com.