why- Open BSD .rocks

sensorsd(8) (∞)

sensorsd — hardware sensors monitor

The sensorsd utility retrieves sensor monitoring data like fan speed, temperature, voltage and RAID logical disk status from the sysctl(2) hw.sensors subtree. When the state of any monitored sensor changes, an alert is triggered. Every alert logs a message to syslog(3) using the daemon facility. Optionally, an alert can be configured to execute a command.