While developing React Native apps (or Ionic Framework) I really dislike opening Android Studio on my Mac just to launch an emulator.
To avoid this, I use this workflow:
# Put this in your `~/.bash_profile`
export ANDROID_HOME=/Users/YOUR_USER_DIRECTORY_HERE/Library/Android/sdk
# NOTE: To use this right away in the same terminal or any currently open terminal, you'll need to source it:
> source ~/.bash_profile
# Now, see what emulators you have:
> $ANDROID_HOME/emulator/emulator -list-avds
# You'll get a list like this:
Pixel_XL_API_28
Pixel_XL_API_27
# Now launch one of the emulators
> nohup $ANDROID_HOME/emulator/emulator -avd Pixel_XL_API_28 &>/dev/null &
That's all it takes to get an Android emulator up and running in a few seconds.