How can I download a file from Heroku bash?

I ran a ruby script from Heroku bash that generates a CSV file on the server that I want to download. I tried moving it to the public folder to download, but that didn't work. I figured out that after every session in the Heroku bash console, the files delete. Is there a command to download directly from the Heroku bash console?

If you manage to create the file from heroku run bash, you could use transfer.sh.

You can even encrypt the file before you transfer it.

cat <file_name> | gpg -ac -o- | curl -X PUT -T "-" https://transfer.sh/<file_name>.gpg

And then download and decrypt it on the target machine

curl https://transfer.sh/<hash>/<file_name>.gpg | gpg -o- > <file_name>

There is heroku ps:copy:

#$ heroku help ps:copy 
Copy a file from a dyno to the local filesystem

USAGE
  $ heroku ps:copy FILE

OPTIONS
  -a, --app=app        (required) app to run command against
  -d, --dyno=dyno      specify the dyno to connect to
  -o, --output=output  the name of the output file
  -r, --remote=remote  git remote of app to use

DESCRIPTION
  Example:

       $ heroku ps:copy FILENAME --app murmuring-headland-14719

Example run:

#$ heroku ps:copy app.json --app=app-example-prod --output=app.json.from-heroku
Copying app.json to app.json.from-heroku
Establishing credentials... done
Connecting to web.1 on ⬢ app-example-prod... 
Downloading... ████████████████████████▏  100% 00:00 

Caveat

This seems not to run with dynos that are run via heroku run.

Example

#$ heroku ps:copy tmp/some.log --app app-example-prod --dyno run.6039 --output=tmp/some.heroku.log
Copying tmp/some.log to tmp/some.heroku.log
Establishing credentials... error
 ▸    Could not connect to dyno!
 ▸    Check if the dyno is running with `heroku ps'

It is! Prove:

#$ heroku ps --app app-example-prod
=== run: one-off processes (1)
run.6039 (Standard-1X): up 2019/08/29 12:09:13 +0200 (~ 16m ago): bash

=== web (Standard-2X): elixir --sname dyno -S mix phx.server --no-compile (2)
web.1: up 2019/08/29 10:41:35 +0200 (~ 1h ago)
web.2: up 2019/08/29 10:41:39 +0200 (~ 1h ago)

I could connect to web.1 though:

#$ heroku ps:copy tmp/some.log --app app-example-prod --dyno web.1 --output=tmp/some.heroku.log
Copying tmp/some.log to tmp/some.heroku.log
Establishing credentials... done
Connecting to web.1 on ⬢ app-example-prod... 
 ▸    ERROR: Could not transfer the file!
 ▸    Make sure the filename is correct.

So I fallen back to using SCP scp -P PORT tmp/some.log user@host:/path/some.heroku.log from the run.6039 dyno command line.

Heroku dyno filesystems are ephemeral, non-persistant and not shared between dynos. So when you do heroku run bash, you actually get a new dyno with a fresh deployment of you app without any of the changes made to ephemeral filesystems in other dynos.

If you want to do something like this, you should probably either do it all in a heroku run bash session or all in a request to a web app running on Heroku that responds with the CSV file you want.