Bash grep file for string and use each as a variable in another commands - bash

Question

In HA configuration I am checking periodically for VIP address on eth0, (lets call it 2.2.2.2). If it is up, then I need to bring up another group of IP address defined for eth0 in /etc/network/interfaces configuration file:
up ip addr add **1.2.3.34** dev $IFACE
up ip addr add **1.2.3.40** dev $IFACE
up ip addr add **1.2.3.48** dev $IFACE
and pass each IP only to another group of commands:
ip a a **1.2.3.34/32** dev eth0
ip a a **1.2.3.40/32** dev eth0
ip a a **1.2.3.48/32** dev eth0
What I've done so far is:
#!/bin/bash
STATUS=$(ip a s eth0 | grep inet | awk '{print $2}' | sed 's/addr://')
if ip a s eth0 | grep inet | awk '{print $2}' | sed 's/addr://' | grep 2.2.2.2/27 ; then
cat /etc/network/interfaces | grep -o "up ip addr add [0-9]*\.[0-9]*\.[0-9]*\.[0-9]*" | grep -o "[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*" > /tmp/ext_ip.txt
Now I need help how to pass each line to another command mentioned above (ip a a 1.2.3...), but have no idea how to do this properly.
Optionally I'd like to revert operation if VIP is not present in the system - in case if primary HA host will go offline.

Answer 1

One way to achieve this would be to parse all IP addresses into an array and use a for loop to assign them to the interface:
#!/bin/bash
IFACE='eth0'
VIP='192.168.0.1'
IFACES_FILE='/etc/network/interfaces'
STATUS=$( ip address show "$IFACE" | grep -o "$VIP" )
if [ ! -z "$STATUS" ]; then
ip_addresses=( $( grep -o '[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*' "$IFACES_FILE" ) )
for ip in "${ip_addresses[#]}"; do
ip address add "$ip" dev "$IFACE"
done
fi
This is a simplified example. You may want to add more checks, add some logging messages to provide output useful for debugging. Also, depending on your server configuration some commands may not work without sudo.

Answer 2

Thanks Andrii L. I've improved your solution to:
#!/bin/bash
IFACE='eth0'
VIP='2.2.2.2'
IFACES_FILE='/etc/network/interfaces'
STATUS=$( ip address show "$IFACE" | grep -o "$VIP" )
if [ ! -z "$STATUS" ]; then
ip_addresses=( $( grep -o 'up ip addr add [0-9]*\.[0-9]*\.[0-9]*\.[0-9]*' "$IFACES_FILE" | grep -o '[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*' ) )
for ip in "${ip_addresses[#]}"; do
ip address add "$ip"/32 dev "$IFACE"
done
else
for ip in "${ip_addresses[#]}"; do
ip address del "$ip"/32 dev "$IFACE"
done
fi
otherwise it is trying to add all IPs and broadcasts found in /etc/network/interfaces file.