Script to run a Minecraft server in a screen session

ftbr-start.sh

#!/bin/bash
cd /opt/ftbr-minecraft
sudo -u minecraft _0="$0" /bin/bash ./serverstarter.sh $*

serverstarter.sh

#!/bin/bash
# partially borrowed from https://minecraft.gamepedia.com/Tutorials/Server_startup_script

# Config
###############################################################################

# java binary
_java=/usr/lib/jvm/adoptopenjdk-8-hotspot-jre-amd64/bin/java

# screen session name
_screenS=ftbr-minecraft

###############################################################################

start_server() {
        screen -dmS $_screenS \
                $_java \
                -server \
                -XX:+UseG1GC \
                -XX:+UnlockExperimentalVMOptions \
                -Xmx4096M \
                -Xms4096M \
                -jar forge-1.12.2-14.23.5.2846-universal.jar nogui
}

###############################################################################

# set script name to calling script if _0 is set
[[ "$_0" == "" ]] && _0="$0"

stop_server() {
        screen -p 0 -S $_screenS -X eval 'stuff "say Shutting down and saving map..."\\015'
        screen -p 0 -S $_screenS -X eval 'stuff "save-all"\\015'
        screen -p 0 -S $_screenS -X eval 'stuff "stop"\\015'
}

check_screen() {
        screen -S $_screenS -Q 'select .' > /dev/null 2>&1
        return $?
        # 0 = running, 1 = not-running
}

usage() {
        echo "Usage: $_0 [command]"
        echo
        echo "Commands:"
        echo "    start  - start server"
        echo "    stop   - stop server"
        echo "    check  - check if server is running"
        echo "    attach - attach to screen session"
}

# parse commands
case $1 in
        ""|start)
                if check_screen; then
                        echo
                        echo "----------------------------------------------"
                        echo "SERVER RUNNING: The server is already running."
                        echo "----------------------------------------------"
                        echo
                        usage
                        echo
                else
                        echo "Starting minecraft server in screen..."
                        start_server
                        echo "Use '$_0 help' to see commands."
                fi

                echo "Use '$_0 attach' to reattach."
                ;;

        stop)
                if check_screen; then
                        echo "Stopping server..."
                        stop_server
                else
                        echo "Server is not running."
                fi
                ;;

        check|status)
                if check_screen; then
                        echo "Server is running."
                        echo "Use '$_0 attach' to reattach."
                else
                        echo "Server is not running."
                        echo "Use '$_0 start' to start."
                fi
                ;;

        attach)
                if check_screen; then
                        echo
                        echo "Use  [ctrl-a] [d]  to detach."
                        echo
                        sleep 1
                        screen -S $_screenS -x
                else
                        echo "Server is not running."
                        echo "Use '$_0 start' to start."
                fi
                ;;

        help|usage)
                usage
                ;;

        *)
                echo "Error: invalid command, '$1'."
                echo
                usage
                exit 1
                ;;
esac