Using Prism Launcher via the Command Line

Usage: prismlauncher [-h] [-v] [-d dir] [-l launch] [-s server] [-a profile] [-I import] [--show show] [--alive] [--help-all]

Options:
  -d, --dir directory    Use a custom path as application root (use '.' for current directory)
  -l, --launch instance  Launch the specified instance (by instance ID)
  -s, --server address   Join the specified server on launch (only valid in combination with --launch)
  -a, --profile profile  Use the account specified by its profile name (only valid in combination with --launch)
  --alive                Write a small 'live.check' file after the launcher starts
  -I, --import file      Import instance from specified zip (local path or URL)
  --show show            Opens the window for the specified instance (by instance ID)
  -h, --help             Displays help on commandline options.
  --help-all             Displays help, including generic Qt options.
  -v, --version          Displays version information.

What is an instance ID, and where do I find it?

The instance ID is the name of the folder where your instance is contained.

To find it, right-click on the instance you want to know the ID of, and then click on Instance Folder within the context menu.

Now, just copy the name of the folder that opened.

Prism Launcher is still opening after I close Minecraft

Currently, the Close Prism Launcher after game window opens option opens Prism Launcher after closing Minecraft, even when launched from the CLI.

To disable this, open Settings, then select Minecraft, and finally, un-check Close Prism Launcher after game window opens or check Quit the launcher after game window closes.