bash script to change interface to 100baseTx given its mac address

changeLineSpeed.sh

#!/usr/bin/env bash 
set -eu -o pipefail 
 
# this is the mac address of the interface we're interested in 
MAC_OI="20:47:47:f8:f4:71" 
 
for i in /sys/class/net/* ; do 
        I_MAC=$(cat $i/address) 
        INTERFACE=$(basename $i/) 
        if [ "$MAC_OI" = "$I_MAC" ]; then 
                ETH_INTERFACE=$INTERFACE 
        fi 
done 
mii-tool -F 100baseTx-FD ${ETH_INTERFACE} 
ethtool -s ${ETH_INTERFACE} speed 100 duplex full