Sidekiq file access

I have an application on Heroku that has a Postgres database and sidekiq running on a hosted Redis instance.

A tool I want to rely on is able to generate JSON output when an output file is specified but it will also print to stdout the non-JSON output. Before deploying the app to Heroku, I was passing a temporary file as output to the tool, opening the file and processing the JSON contents and finally deleting it, but now on Heroku, sidekiq doesn't have access to files.

Since I just want the JSON data, is there a way to run the tool and just process the JSON output without using an object storage service like S3 and having to deal with tmp files? Alternatively, is there a way to do something like passing a memory mapped file to the output file option of the tool and read it from memory?

Thank you