jq snippets

jq is a query language for json. I have collated various samples from around the web and through experience but the basis of my learning came from these two resources source 1 and source 2.

Changing property values

Change the property value for all items in a json collection and pipe the results to a file

Sample input-1.json

[
    {
        "property" : "something"
    },
    {
        "property" : "something else"
    }
]

jq '.[].property = "false"' input-1.json > output.json

Change the property value for all items in a collection property and pipe the results to a file

Sample input-2.json

{
    "MyArray": 
    [
        {
        "property" : "something"
},
    {
        "property" : "something else"
    }
    ]
}

Select items from an array where the id is not null from file.json

jq '.[] | select(.id != null)' file.json

with quotes:

jq '.resources[] | select(.name=="my_api_appreg")'

using against a terraform state file:

terraform state pull | jq '.resources[] | select(.name=="my_api_appreg") | .instances[].attributes.app_role[] | select(.display_name=="Service Daemon") | .id'

Select items with unique id, description, displayName and value as a composite key from file.json and return the results as an array

jq '[.[]] | unique_by(.id) | unique_by(.description) | unique_by(.displayName) | unique_by(.value)' file.json

Merge two json array files together

jq -s '.[0] + .[1]' in.json file.json

How to select specific properties

jq '.[] | {description: .description, displayName: .displayName, allowedMemberTypes: .allowedMemberTypes, id: .id}' file.json

collect all results as one array

jq '[.[] | {description: .description, displayName: .displayName, allowedMemberTypes: .allowedMemberTypes, id: .id}]' file.json

with a filter

jq '.[] | {description: .description, displayName: .displayName, allowedMemberTypes: .allowedMemberTypes, id: .id} | select(.id == null)' file.json

group into separate arrays where based on display names

jq '[.[] | {description: .description, displayName: .displayName, allowedMemberTypes: .allowedMemberTypes, id: .id}] | group_by(.displayName)' file.json

get unique values. precedence of what will be included is based on the results of a group_by. the first element will be kept

jq '[.[] | {description: .description, displayName: .displayName, allowedMemberTypes: .allowedMemberTypes, id: .id, value: .value}] | unique_by(.value)' in3.json

Length of an array

jq length <file>

jq length <<< $variable

Pipe in a command to jq

# get health logs from a docker container
docker inspect mycontainer | jq '.[].State.Health'