Filter, reshape and stream JSON from a shell.

jq

Extract one field from a stream

curl -s https://api.example.com/items | jq -r '.items[].name'

-r writes raw strings instead of quoted JSON. Without it names come back wrapped in escape sequences.

Filter before you extract

jq -r '.items[] | select(.state == "ready") | .id'

Fail loudly instead of printing null

jq -e -r '.token' config.json

-e sets the exit status from the result. A missing key becomes exit 4, which stops a script that would otherwise carry null into the next command.

Work with objects without a schema

jq 'keys' payload.json
jq 'to_entries | map(select(.value > 100)) | from_entries' metrics.json

Scope: jq