https://antranigv.am/posts/2025/06/1087/
A while back I needed to get the input voltage from one of our UPSes, so I used bsnmpwalk(1) to get the information needed and ran it in a script with a loop and sleep. Running it in tmux(1), of course.
#!/bin/shlastoff="maybe"while true;do inpvol=$(bsnmpwalk -o quiet -s public@172.20.42.101 1.3.6.1.2.1.33.1.3.3.1.3) [ $? != 0 ] && \ curl -s -X POST \ https://api.telegram.org/botXXX:YYY/sendMessage \ -d chat_id=-ZZZ \ -d text="Something is wrong with the SNMP server" [ "${inpvol}" -lt 200 ] && \ curl -s -X POST \ https://api.telegram.org/botXXX:YYY/sendMessage \ -d chat_id=-ZZZ \ -d text="Power seems to be off. I see Input Voltage as ${inpvol}" && \ lastoff="true" [ "${inpvol}" -ge 200 ] && [ "${lastoff}" == "true" ] && \ curl -s -X POST \ https://api.telegram.org/botXXX:YYY/sendMessage \ -d chat_id=-ZZZ \ -d text="Power back on. I see Input Voltage as ${inpvol}" && \ lastoff="false" printf "%s --- %s\n" "$(date)" "${inpvol}" sleep 60doneThis got the job done, but I guess there’s place for improvement (leave a reply).
Anyways, I kept forgetting that I need to run the script in tmux after reboots, so I decided to use daemon(8).
touch /etc/rc.localchmod +x /etc/rc.localcat - >> /etc/rc.local#!/bin/shdaemon -u nobody -r -R 5 -f -t ups-notifier -o /var/log/ups_notifier.log /usr/local/bin/ups_notifier.shAgain, there’s a place for improvement, specifically I can use a proper rc.d(8) script, yet again, this gets the job done.
Gotta say, I love the simplicity of FreeBSD.
