Determine username from RStudio running on docker

I am running a docker container in Azure Apps that requires Single Sign On to access. I can write to a database, but need to know the user who made the write, which is based on the SSO username.

Is there a way to extract this info in a live session?

I tried running Sys.getenv() and viewing under USER, but the result it rstudio

I also tried searching /usr/bin/env but did not find anything there.

Can anyone offer any possible solutions?