Minecraft Paper server startup script using GNU Screen (compatible with Linux and WSL on dual boot systems)

start.sh

#!/bin/bash
windowspath=#Windows-equivalent server path goes here
linuxpath=#Linux-equivalent server path goes here

winhost=#WSL hostname goes here

#Check if the server is already running
if $(screen -list | grep -q minecraft); then
	exec screen -x minecraft
else
	#Check what OS is currently running
	if [[ $(uname -n) == "$winhost" ]]; then
		serverpath=$windowspath
	else
		serverpath=$linuxpath
	fi

	#Create update directory if it doesn't exist
	if [ ! -d "$serverpath/update" ]; then
		mkdir $serverpath/update
	fi

	#Check for server updates
	cd $serverpath/update
	version=#Server version goes here
	URL="https://papermc.io/api/v1/paper/$version/latest/download"
	fetch=$(wget --spider --server-response $URL 2>&1 | grep -i content-disposition)
	remoteversion=$(echo $fetch | cut -d'=' -f 2)
	if ! [[ $remoteversion == $(cat currentversion.txt) ]] ; then
		while true; do
			read -p "Paper update available. Download? [Y/n] " yn
			case $yn in
				[Nn]* ) break;;
				* ) echo Downloading update...
				wget --content-disposition $URL
				ls | grep ".jar" > currentversion.txt
				mv *.jar ../paper.jar
				break;;
			esac
		done
	fi

	#Start the server in a screen
	if [ -z "$STY" ]; then
		screen -mS minecraft /bin/bash -c "
		cd $serverpath
		exec java -jar -Xms4G -Xmx4G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true paper.jar -nogui"
	fi
fi