Export the metafields of all products in your Shopify store to a JSONL file using Shopify Development Tools (https://github.com/ScreenStaring/shopify-dev-tools)

export-product-metafields.sh

#!/bin/bash

#
# Export the metafields for products in your Shopify store to a JSONL file.
# Can be modified to output to a file per product or to text file(s).
# See Shopify Development Tools (sdt) for more infomation.
#
# By ScreenStaring (http://screenstaring.com)
#
#
# This script requires Shopify Development Tools: https://github.com/ScreenStaring/shopify-dev-tools
#

export SHOPIFY_SHOP=your-store
# Add your credentials here. For more information see: https://github.com/ScreenStaring/shopify-dev-tools#credentials
export SHOPIFY_API_TOKEN=your-token

# Note the sdt will exit 0 on usage (cli lib bug)
set -e

sdt products export ids

for id in $(cut -f1 -d, "$SHOPIFY_SHOP.csv" | egrep '^[0-9]+$'); do
    echo "Retrieving metafields for product $id"
    # Requires v0.0.3 or greater
    sdt metafield product -j "$id" >> product-metafields.jsonl
done