Can't find document created in docker sqlplus running against docker oracle12c

I’m using docker exec sqlplus to start sqlplus running against a docker container that has oracle12c. I am connecting, I’m able to do all kinds of good things.

However, I’ve done a SPOOL to create a file of the data of a very large file. That works. If I do
sqlplus> host ls
I see my file.

However, I cannot find it anywhere on my hard drive.

sqlplus> host whomai . says I am root
sqlplus> host pwd . says I am in /

Where is this mythical place? How can I get to that file I created?

I figured it out!!
docker cp did the trick for me.