7 * * * * /usr/local/sbin/update-home-ip cron

update-home-ip

#!/bin/bash -eu

progname="$(basename "$0")"
die() { printf >&2 "%s: %s\n" "$progname" "$*" ; exit 1; }

if [[ $# -gt 0 && "$1" == "cron" ]]; then
  sleep $((10 + RANDOM % 40 ))
fi

dynhost=CENSORED
dynpass='CENSORED'
myip=$(curl -sS 'https://www.icanhazip.com/')


if [[ ! "${myip:?}" =~ ^[0-9.]+$ ]]; then
  die "IP derivation did not give an IP address" "$myip"
fi

# curl -k is insecure, but it's a self-signed cert, just get protection against
# sniffing, not active attacks

set +e
result="$(
  curl -k -sS --basic -u "${dynhost:?}:${dynpass:?}" \
  "https://dyn.dns.he.net/nic/update?system=dyndns&hostname=${dynhost:?}&myip=${myip:?}"
)"
retval=$?

case $retval in
0) priority=daemon.info ;;
*) priority=daemon.err ;;
esac

logger -p $priority "$progname update of ${dynhost:-?} to ${myip:-?} exited $retval and yielded: $result"