anonymize ethernet mac address

macanon.sh

#!/bin/bash
# thanks microsoft copilot. worked from first try. prompt:
# can you write a small script in a language of your choice that takes input as defined by the name of the input file, searches for patterns that resemble an ethernet mac address including those that omit the zero, such as like when netstat on macos does, then replace the last three octets of the mac address with xx:xx:xx
# it wrote python but python requires xcode so I asked for a rewrite in bash

filename="$1"

# MAC address pattern (with optional leading zeros)
pattern="([0-9A-Fa-f]{1,2}[:-]){5}([0-9A-Fa-f]{1,2})"

# Read file line by line
while IFS= read -r line
do
    if [[ $line =~ $pattern ]]; then
        # Extract MAC address
        mac="${BASH_REMATCH[0]}"
        # Split MAC address into octets
        IFS=':' read -ra octets <<< "$mac"
        # Replace last three octets
        new_mac="${octets[0]}:${octets[1]}:${octets[2]}:xx:xx:xx"
        # Replace MAC address in line
        line="${line//$mac/$new_mac}"
    fi
    echo "$line"
done < "$filename"