Field reference sprintf example

Hi there,

I'm currently using the http output plugin to send notifications to a monitoring solution whenever topbeat signals disk usage > some percentage.

I reference the field like so: %{[fs][used_p]}, but then the monitoring app sees the percentage like


and similar.

I need it to be


How cant I achieve this using the sprintf syntax? I have found no examples in the docs, so I fell kinda lost

I don't think this is possible without using a ruby filter to format the float into a custom string field and use that later on.