How to Use JQ to find Key based on Value

USECASE

The aim of this page is to explain how to use jq to find a key based on a value in JSON data retrieved from Consul.

Consul KV Store: Used to store key-value pairs.

JSON Data: Example JSON data retrieved from Consul.

{
  "a3e705d1-98d3-4c58-80a4-f9f9c9ec3e47": "CUSTOMER_1",
  "d4b7e8e9-1b50-4f3d-b3d9-ea6b5feca1bd": "CUSTOMER_2",
  "b21c9e36-4798-4387-ae1e-f6c678b0c14e": "CUSTOMER_3"
}

Objective: Find the key corresponding to a specific value.

jq Command: Tool for processing JSON data.

Basic jq Command:

jq -r 'to_entries[] | select(.value == "VALUE_YOU_ARE_LOOKING_FOR") | .key' yourfile.json

Integrating with Consul:

consul kv get global/uuid-to-customer-name | jq -r 'to_entries[] | select(.value == "VALUE_YOU_ARE_LOOKING_FOR") | .key'

Example Value: Searching for the value "anonymized_customer".

Step-by-Step Breakdown:

• Retrieve JSON from Consul:

consul kv get global/uuid-to-customer-name

• Convert JSON to Key-Value Pairs:

consul kv get customer-uuids | jq -r 'to_entries[]'

• Output:

{
  "key": "a3e705d1-98d3-4c58-80a4-f9f9c9ec3e47",
  "value": "CUSTOMER_1"
}
{
  "key": "d4b7e8e9-1b50-4f3d-b3d9-ea6b5feca1bd",
  "value": "CUSTOMER_2"
}
{
  "key": "b21c9e36-4798-4387-ae1e-f6c678b0c14e",
  "value": "CUSTOMER_3"
}

• Filter for Specific Value:

consul kv get global/uuid-to-customer-name | jq -r 'to_entries[] | select(.value == "anonymized_customer")'

• Output:

{
  "key": "cde71158-f1d6-4707-88e0-28d1716f2790",
  "value": "anonymized_customer"
}

• Extract the Key:

consul kv get global/uuid-to-customer-name | jq -r 'to_entries[] | select(.value == "anonymized_customer") | .key'

• Output:

cde71158-f1d6-4707-88e0-28d1716f2790

LINKS

• jq
• Consul KV Store Commands