Exporting firebase data to json

I'm trying to export a particular Firestore collection using gcloud Right now, I did

gcloud storage buckets create gs://my-bucket 
gcloud firestore export gs://my-bucket --collection-ids=my-collection 
gcloud storage cp -r gs://my-bucket/2022-09-22T09:20:16_11252 my-directory

which results in some content in my-directory/all_namespaces/.../output-1. The output-1 file definitely seems to contain some relevant data but it is not very readable. Hence some questions:

which file format is used?
can I export to JSON (or CSV or XML) directly
can I convert the current file to JSON, CSV or XML

And related

why is output-0 empty?

Solution

Surprisingly, there don't seem to be a lot of LevelDB tools available so exporting to LevelDB format is not convenient.

I managed to export to csv by adding two extra steps: loading and extracting to/from BigQuery. So I now do something like

# create bucket
gcloud storage buckets create gs://my-bucket 

# firestore export
gcloud firestore export gs://my-bucket/my-prefix --collection-ids=my-collection 

# create dataset
bq mk --dataset my_dataset

# load bucket into BigQuery
bq load --replace --source_format=DATASTORE_BACKUP my_dataset.input \
gs://my-bucket/my-prefix/all_namespaces/.../....export_metadata

# export BigQuery as csv to bucket
bq extract --compression GZIP 'my_dataset.input' gc://my-bucket/results.csv

# download csv file
gcloud storage cp -r gc://my-bucket/results.csv <local-dir>