Add field to every element

Inject a new key-value pair into every array element

jq '[.[] | . + {"env": "prod"}]' items.json

More jq commands

Walk and transform all strings

jq 'walk(if type == "string" then ascii_downcase else . end)' data.json

Recursively lowercase all string values in a JSON document
Pretty print JSON

cat data.json | jq '.'

Format and colorize a JSON file
Filter by field

cat data.json | jq '.items[] | select(.status == "Running")'

Select objects where a field equals a value
Extract specific fields

cat data.json | jq '[.items[] | {name:.metadata.name, ns:.metadata.namespace}]'

Project only specific fields into a new array
Group by field

cat data.json | jq 'group_by(.namespace) | map({ns: .[0].namespace, count: length})'

Aggregate items by a field value