How to check if service is enabled with launchd

Question

I can't figure out how to check from within C/C++ if a service is enabled via launchd. I know I can use launchctl from the command line and am currently executing ' launchctl list myServiceName ' from fork/exec.

I've found that boostrap_look_up() might be the way to check this but I can't find enough documentation to condense this down to a simple example.

Can you shed light on this? All I need is a small function to test if my service is actually registered and available.

Answer 1

Apple has open sourced launchd and the source code is available at http://opensource.apple.com/source/launchd/launchd-442.26.2/

The source code for launchctl is in support/launchctl.c. Hopefully you should be able to find what you need in there. I suspect you need to look at the list_cmd function about two thirds of the way down the file.

If the answer isn't in launchctl.c then I really don't know where else it would be.

---

Initially I started looking for symbols in the launchctl binary.

The bootstrap_look_up() function you mention appears to be defined in launchd/liblaunch/libbootstrap.c.

Running nm /bin/launchctl provides a number of interesting symbols:

             ...
             U _bootstrap_get_root
             U _bootstrap_info
             U _bootstrap_look_up_per_user
             U _bootstrap_lookup_children
             U _bootstrap_parent
             U _bootstrap_port
             ...
             U _launch_data_alloc
             U _launch_data_array_get_count
             U _launch_data_array_get_index
             U _launch_data_array_set_index
             U _launch_data_copy
             U _launch_data_dict_insert
             U _launch_data_dict_iterate
             U _launch_data_dict_lookup
             U _launch_data_dict_remove
             U _launch_data_free
             U _launch_data_get_bool
             U _launch_data_get_errno
             U _launch_data_get_fd
             U _launch_data_get_integer
             U _launch_data_get_machport
             U _launch_data_get_opaque
             U _launch_data_get_opaque_size
             U _launch_data_get_real
             U _launch_data_get_string
             U _launch_data_get_type
             U _launch_data_new_bool
             U _launch_data_new_fd
             U _launch_data_new_opaque
             U _launch_data_new_string
             U _launch_data_set_bool
             U _launch_data_set_integer
             U _launch_data_set_opaque
             U _launch_data_set_real
             U _launch_data_set_string
             U _launch_msg
             ...

These launch_data_ functions appear to be declared in launchd/launch/liblaunch.c.

As far as I can tell liblaunch is not installed as a system library and libSystem doesn't appear to contain these symbols either (just bootstrap_init is exported).

I would suggest downloading the launchd source, compiling your own liblaunch and seeing if you can get the functionality you require by linking it to your project. I have no idea if this will do what you want.