Check if file isn't being updated

Hi -

I’m trying to create a Grafana Dashboard telling me how old a file is. Additionally, I’d also like to set up a Kapacitor Alert to tell me if the file’s last modified time is greater than a particular value.

Currently I’ve been using the filestat input plugin in Telegraf to get data about the file, which gives me back a modification_time or the number of seconds since the “beginning of time”. Where as really what I’m interested in is more of, time since last update. So essentially I’d need someway to diff the last_modified_time to the current_time.

Is there a way to do this?

Thanks in advanced!