There are ports that do this with more features, but I thought others might like to do it in base with no added software. I've been using this script since 4.2 and it works OK:
#!/bin/ksh # Cron this script to run every X minutes. Written for OpenBSD. # Get Current IP lynx -dump http://checkip.dyndns.org:8245/ | awk '{print $4}' | sed '/^$/d' > ip_new.txt # compare new with old diff ip_new.txt ip_old.txt # if different, send update if [ $? -ne 0 ] then #echo "The IP has changed" ip=$(cat ip_new.txt) # Following two lines are optional. Log date of change and IP history. date >> ip_date.txt cat ip_old.txt >> ip_history.txt curl --insecure "https://user:p...@members.dyndns.org/nic/update?hostname=host.xxx&myip=$ip&wildcard=NOCHG&mx=NOCHG&backmx=NOCHG"; fi # Whether a change has occurred or not, overwrite old with new cp ip_new.txt ip_old.txt
