iOS simulators boot, but don't appear, with "xcrun simctl boot ${UUID}"

Question

I run this script

#!/usr/bin/env bash

device1="B13D4F22-AA4E-4890-8C2B-3C5B7B6E3678"
device2="5E2588E9-38B5-48AF-99C5-DEE8A1E6FDA0"
device3="2C28BD02-18BE-4FC5-94DE-075880E70E60"
device4="723705CD-B038-44E0-B42E-F1D29A28E85E"

xcrun simctl boot ${device1}
xcrun simctl boot ${device2}
xcrun simctl boot ${device3}
xcrun simctl boot ${device4}

and the output is

An error was encountered processing the command (domain=com.apple.CoreSimulator.SimError, code=164): Unable to boot device in current state: Booted An error was encountered processing the command (domain=com.apple.CoreSimulator.SimError, code=164): Unable to boot device in current state: Booted An error was encountered processing the command (domain=com.apple.CoreSimulator.SimError, code=164): Unable to boot device in current state: Booted An error was encountered processing the command (domain=com.apple.CoreSimulator.SimError, code=164): Unable to boot device in current state: Booted

However, there is no "Xcode" icon in the dock, and I see no sims on the mac. How can they be booted? Why don't they appear?

Answer 1

xcrun simctl boot $udid only launch the simulator background service,

exec open Simulator.app to launch the foreground GUI.