Recover, restart and upgrade your process via exit codes with bash

loop.sh

	#!/bin/bash
	
	
	# switch to config directory
	
	while true; do
  # Of course you can use any other executable file here. We use java.
		java \
				-Xms256m \
				-Xmx2048m \
				<jvm args> \
				-jar ./my_jar.jar
	
		code=$?
	
		case $code in
			0) # proper shutdown
				echo "Performed proper shutdown, exiting restart loop"
				exit 0
			;;
			10) # restart request
				echo "Requested to restart"
				continue
			;;
			20) # upgrade requested
				echo "Requested to upgrade"
				./upgrade.sh
				continue
			;;
			*) # Recovering
				echo "Unknown exit code, attempting recovery restart in a few seconds"
				sleep 2
				continue
			;;
		esac
	done

start.sh

#!/bin/sh
#rm screenlog.0

cd "$(dirname "$0")"
# set your screen name
screen -dmS <screen_name> \
	./loop.sh

upgrade.sh

#!/bin/bash

# this requires that you clone the git repository to a directory names repo
# To do this you need to execute
# git clone <remote_url> repo

BRANCH=${1:-master}
cd repo
git fetch --all
git checkout $BRANCH
git reset --hard origin/$BRANCH
git pull -f --no-rebase
./gradlew clean <shadowJar/build> --no-build-cache --refresh-dependencies
cd ..
# replace the my_jar name with the name of your jar file without the version numbers.
# this will select the matching file. when your build process outputs multiple jar you need to define the file name with the classifier
mv repo/build/libs/my_jar*.jar my_jar.jar