backup mysql databases inside docker containers

mysqlbackup_docker.sh

#!/bin/bash


mysql_containers=`docker ps  -f  ancestor=mysql:8.0 --format '{{.ID}}:{{.Names}}'`

for i in $(echo $mysql_containers)
do
		echo $i
	        arr=($(echo $i | sed "s/:/ /g"))
	        if [ "${#arr[@]}" -eq "2" ]; then
				docker exec ${arr[0]} sh -c 'exec mysqldump -uroot -p"$MYSQL_ROOT_PASSWORD" --all-databases' > /mysqlbackups/${arr[1]}.sql
				gzip -9f /mysqlbackups/${arr[1]}.sql
		fi
done