export into json

mongoexport --uri="mongodb://username:password@localhost:27017/database_name" \
            --collection=collection_name \
            --fields=field1,field2 \
            --out=output_file.json

export into csv

mongoexport --uri="mongodb://username:password@localhost:27017/database_name" \
            --collection=collection_name \
            --type=csv \
            --fields=field1,field2 \
            --out=output_file.csv