I want to set the custom priority level (i.e. nice) to a particular program as the default priority level. The tricky thing is that the process is not started by me but by background processes not under my control. Is it possible?
See the section 5 man page for launchd.plist -- we can specify the nice value in the config plist for that process. If the process is kicked off by something other than launchd itself, then... we may be out of options.