How wait for eth0 interface before running "ip link", "ip addr" and "ip route" commands?

Here's the solution I eventually solved my problem with:

while ! ip link show eth0 | grep -q 'state UP'; do
    sleep 1
done

ip link add macvlan0 link eth0 type macvlan mode bridge
ip addr add 192.168.0.240/32 dev macvlan0
ip link set macvlan0 up
ip route add 192.168.0.240/28 dev macvlan0

However, I had 2 "boot-up" scheduled tasks on my Synology and I was getting some errors at boot-up. To solve that issue I configure this task to have the other one as pre-task. In other words, the tasks executed in sequence, waiting for the previous task to finish before starting the new one.

Check the status of eth0 from /sys/class/net/eth0/operstate and wait until the network interface to be up:

while ! [ "$(cat /sys/class/net/eth0/operstate)" = "up" ] 
do
    echo  "waiting for eth0 to be up"
    sleep 2
done

ip link add macvlan0 link eth0 type macvlan mode bridge
ip addr add 192.168.0.240/32 dev macvlan0
ip link set macvlan0 up
ip route add 192.168.0.240/28 dev macvlan0