Some folks have had trouble finding them, so here are the various commands that can be used with the Mac BOINC core client.
-attach_project
Attach this computer to a new project. You must have an account with that project. You will be asked for the project URL and the account ID.
-show_projects
Print a list of projects to which this computer is attached.
-detach_project URL
Detach this computer from a project.
-reset_project URL
Clear pending work for a project. Use this if there is a problem that is preventing your computer from working.
-update_prefs URL
Contact a project's server to obtain new preferences. This will also report completed results and get new work if needed.
-return_results_immediately
Contact scheduler as soon as any result done.
-run_cpu_benchmarks
Run CPU benchmarks. Do this if you have modified your computer's hardware.
-check_all_logins
If 'run if user active' preference is off, check for input activity on all current logins; default is to check only local mouse/keyboard
-exit_when_idle
Get, process and report work, then exit.
-allow_remote_gui_rpc
Allow GUI RPCs from remote hosts
-help
Show client options.
-version
Show client version.