Sh script to output unused interfaces on linux - sh

Question

I asked the dark side and here's what it printed.....
#!/bin/bash
for interface in $(ip addr show | awk '/^[0-9]+:/ {print $2}' | tr -d :)
do
if ! ip addr show $interface | awk '/inet / {print $2}' | grep -q . ; then
echo $interface
fi
done
I want to add n+ variable directly so the output will be the interfaces that is not used by the system,
Done

Answer 1

I have these two scripts, one for Linux and one for Mac, I hope they serve you because I have tested them on Linux Ubuntu and Mac.
on linux
#!/bin/bash
# This script will output unused interfaces on Linux
# Get list of all interfaces
interfaces=$(ifconfig -a | grep -o '^[^ ]*:' | tr -d :)
# Loop through each interface
for interface in $interfaces; do
# Check if interface is up
if [[ $(ifconfig $interface | grep -c 'UP') -eq 0 ]]; then
# Output interface name
echo "$interface is unused"
fi
done
on mac
#!/bin/bash
# Get list of all network interfaces
interfaces=$(networksetup -listallnetworkservices | tail -n +2)
# Loop through each interface
for interface in $interfaces; do
# Get the IP address of the interface
ip=$(ipconfig getifaddr "$interface")
# If the IP address is empty, the interface is unused
if [ -z "$ip" ]; then
echo "$interface is unused"
fi
done

Answer 2

#!/bin/bash
count=0
for interface in $(ip addr show | awk '/^[0-9]+:/ {print $2}' | tr -d :)
do
if ! ip addr show $interface | awk '/inet / {print $2}' | grep -q . ; then
free_interfaces[$count]=$interface
count=$((count + 1))
fi
done
case $count in
0)
echo "No usable interface found."
exit 1
;;
1)
DEFIF=${free_interfaces[0]}
echo "The interface $DEFIF will be used."
;;
*)
echo "Available interfaces to select: "
PS3="Press a number to select an interface to use (1-$count): "
select interface in "${free_interfaces[#]}"; do
DEFIF=$interface
break
done
echo "The interface $DEFIF will be used."
;;
esac