Shell script monitor volume disk size of server

DISKCHECKPCENT=`df --output=pcent /dev/vda2 | egrep -o "[0-9]+"`
if [ $DISKCHECKPCENT -ge 90 ]
then
    curl --location "https://api.telegram.org/xxxxx:yyyyy/sendMessage" \
            --form "chat_id=-zzzzz" \
            --form "text=DISK reach to ${DISKCHECKPCENT}% - please check and upgrade"
fi