nsupdate.info bash script

nsupdate.sh

#!/bin/bash

USER="boci.nsupdate.info"
PASS="YEMLS9Yk2D"
UPDATE_COMMAND="curl -o status.ip -s --user $USER:$PASS --basic https://ipv4.nsupdate.info/nic/update"

curl -s https://ipv4.nsupdate.info/myip -o current.ip

if [ ! -f prev.ip ]
then
        cp current.ip prev.ip
        eval $UPDATE_COMMAND
else
        if ! diff current.ip prev.ip >/dev/null ; then
                rm current.ip
        else
                rm prev.ip
                mv current.ip prev.ip
                eval $UPDATE_COMMAND
        fi
fi