I know it's possible to run pure dex bytecode on an Android command line via /system/bin/dalvikvm, but I wonder if it's possible to run oat files from command line?
Since it's an ELF shared object file it has to be started via zygote I guess. Maybe it's possible with app_process, but I don't know if and how.
Can anyone help me out?
An .oat file in itself is not a complete application. boot.oat that contains the initialized heap is also needed for the app process and so is boot.art. Zygote, as you said the running app_process already has these pages. Zygote is running waiting for requests on the socket /dev/socket/zygote to receive app launch requests. You can look around in AOSP source as to what information is written on this socket by launcher to launch the app and how that information communicates about the app's .oat file.
