Update s3 metadata for an object and preserve existing content meta

update_s3_meta.sh

#!/bin/bash

BUCKET="my-bucket"
KEY="/foo/bar/baz.xml"
FILENAME=$(basename $KEY)

#
# {
#    “ContentType”: “text/xml; charset=utf-8",
#    “CacheControl”: “public, must-revalidate, proxy-revalidate, max-age=0",
#    “ContentEncoding”: “gzip”
# }
#
EXISTING_JSON_DATA=$(aws s3api head-object --bucket "${BUCKET}" --key "${KEY}" | jq '. | {ContentType,CacheControl,ContentEncoding}')

#
# --content-type
# text/xml; charset=utf-8"
# --cache-control
# public, must-revalidate, proxy-revalidate, max-age=0
# --content-encoding
# gzip
#
IFS=$'\n'
PARAM_KV_DATA=($(echo $EXISTING_JSON_DATA | jq -r 'to_entries|map("--\(.key | [splits("(?=[A-Z])")] | map(select(. != "") | ascii_downcase) | join("-"))\n\(.value)")|.[]'))

# update meta with new data and retain existing we retrieved
aws s3api put-object \
        --bucket "${BUCKET}" \
        --key "${KEY}" \
        --content-disposition "attachment;filename=\"${FILENAME}\"" \
        ${PARAM_KV_DATA[@]}