John Pertell shows how to figure out which user account is running SQL Server R Services code:
You’re not running as yourself, even though that’s the account you signed into SSMS as.
You’re not running under the server account that SQL or SQL Launchpad run under.
You’re running as a new account created when you installed SQL R Service In Database for the purpose of running R code.
John also looks at a couple ways of showing which user is running this code and notes that this solves his file share issue.