I have a launch daemon that will need to spawn a tray icon in a users session on OSX. My current problem is: is there a way to get an event whenever a user logs in or logs out? Similar to using logind or consolekit on linux.
The tool you want is a LaunchAgent. LaunchAgents are automatically launched when a user logs in, and shut down when the log out. If you also have a LaunchDaemon, you can use a LaunchAgent to communicate to it from the user context. See Creating Launch Daemons and Agents for full details and how to set it up. Make sure to look at XPC services as well (in the same doc) to understand one way to communicate between processes. You can also use loopback networking, but XPC is more powerful and preferred when appropriate.
If you're building this kind of thing, you definitely want to read the entire Daemons and Services Programming Guide and also TN2083: Daemons and Agents. That tech note is probably the most important document you'll read for this kind of problem. OS X is not like Linux (or BSD) in this regard.
Is there a way to allow multiple instances of an application on macOS?
My app requires the main process and a helper process. On launch, it uses NSTask to launch another copy of itself with a command line parameter to become the helper process.
If the main App crashes, and the helper app is still running, it's impossible for the user to launch the main app again because macOS only allows one instance to run at a time.
Is there any way around this? Either to allow multiple instances in general or to make Finder think the helper process isn't the same as the original process?
I need to write Mac app which will start automatically only in case when another particular app was launched. Could you please provide entry point where to look and what to use. Do I need to have special autostart up process? I am new to Mac app development.
You can add observer using CFNotificationCenterGetDistributedCenter() for example.
Please, take a look at this article, here may be the solution Inter-process communication
I am interested in building a Mac OS X application that requires knowing what applications the user has open and when a new one opens, all when my app is running. It doesn't have to be approved by the Mac App Store (If this violates their use terms). An example of an app that does this is the Rescue Time app.
Thank you for any answers,
Michael Truell
Don't know if you're still trying to needs this, but I did some more research on how to solve this and here is what you could look into:
To get notified when applications are opened by a user, use NSWorkspace's notification center, and add an observer for keys like NSWorkspaceDidActivateApplicationNotification. See the documentation NSWorkspace. You can also use NSWorkspace to get all running applications.
If you need to access information about a running application, you should check out Scripting Bridge, and if you don't care about App Store or sandboxing, check you accessibility api, AX
I am looking for a way to monitor the state of one of my applications on OS X. There's a number of components that I need to monitor such as the status of various communication channels. If they go down, the monitoring process should be able to warn the user both on screen and via a push notification.
XPC services look promising, but if the app crashes, I presume this will take out the service as well, or am I mistaken?
My preferred solution is something which would also monitor for unexpected termination, and restart the app if it happens.
What is the best way to do this?
I think monitoring communication channels, etc. must be done by the each specific components (processes). And if the unexpected error occur that component should exit immediately to ensure proper cleanup.
For processe monitoring, below Apple Technical Q&A document will be really helpful:
Technical Note TN2050: Observing Process Lifetimes Without Polling
You could write an app which starts your main application as a child process, and waits for it to exit. It could check the exit code, and then react according to your needs.
This approach is explained here: https://stackoverflow.com/a/78095/785411
To fork() some monitoring process to run your main application as a child process, this is explained here: https://stackoverflow.com/a/4327062/785411
I think you could possibly make use of the built in facilities Launchd and CrashReporter to achieve your requirements.
Launchd is the OS X system supervisor intended for launching and monitoring background processes, and would be typically used to run XPC services. Launchd agents can react to various system events, and can be configured to restart processes in the event of them crashing ( specified via the KeepAlive/SuccessfulExit key in the property list)
Launchd can be set to react to various system events as launch event, including monitoring files and directories, scheduled times, or listening to network connections.
CrashReporter is the OS X system facility that catches and logs all process crashes. It logs through the AppleSystemLogger facility and can be accessed with the syslog tools as documented in the linked TechNote. On Mountain Lion, user process crash reports end up in ~/Library/DiagnosticReports/ , with a crashlog and plist file pair created per crash event.
I think you could use these features in a couple of ways to achieve your requirement, if launchd is responsible for running the xpc services, it can take reponsibility for restarting them on crash events, and they can be dissociated from any app crashes.
You could write a launchd agent that responds to for crash events by montioring the crash report directory (e.g. using the QueueDirectories property) for new logs and re-launches your applicaton, or presents notifications.
If each process runs in its own thread you could run a watchdog program that monitors whether the threads are alive. A script that runs ps in a loop and parses the output could do it.
You can see the various options here. See for example -C to select by command name, and -m to show all threads.