If you do not already have an instance running, start the emulator:
ffx emu start --headless
When startup is complete, the emulator prints the following message and returns:
Logging to "{{ '<var>' }}$HOME{{ '</var>' }}/.local/share/Fuchsia/ffx/emu/instances/fuchsia-emulator/emulator.log" Waiting for Fuchsia to start (up to 60 seconds)........ Emulator is ready.
