jq: Quick Start and Command Example

This post shows examples of jq usage.

what is jq?

jq is a command-line JSON parser.

It can pretty print JSON, access specified keys & values, etc.

install

% brew install jq
% jq --version
jq-1.6

sample.json

Assume that you have un-formatted json as a API-call result.

[{"name":"n1","created":"2021-02-15","settings":[{"name":"setting1","value":"value1"},{"name":"setting2","value":"value2"}]},{"name":"n2","created":"2021-02-16","settings":[{"name":"setting1","value":"value1"}]}]

examples

pretty format

% cat sample.json | jq .

[
  {
    "name": "n1",
    "created": "2021-02-15",
    "settings": [
      {
        "name": "setting1",
        "value": "value1"
      },
      {
        "name": "setting2",
        "value": "value2"
      }
    ]
  },
  {
    "name": "n2",
    "created": "2021-02-16",
    "settings": [
      {
        "name": "setting1",
        "value": "value1"
      }
    ]
  }
]

remove array bracket

% cat sample.json | jq -r '.[]'

{
  "name": "n1",
  "created": "2021-02-15",
  "settings": [
    {
      "name": "setting1",
      "value": "value1"
    },
    {
      "name": "setting2",
      "value": "value2"
    }
  ]
}
{
  "name": "n2",
  "created": "2021-02-16",
  "settings": [
    {
      "name": "setting1",
      "value": "value1"
    }
  ]
}

select first element of array

% cat sample.json | jq -r '.[0]'

{
  "name": "n1",
  "created": "2021-02-15",
  "settings": [
    {
      "name": "setting1",
      "value": "value1"
    },
    {
      "name": "setting2",
      "value": "value2"
    }
  ]
}

list names

% cat sample.json | jq -r '.[].name'

n1
n2

list names (as array format)

% cat sample.json | jq -r '.[] | [.name]'

[
  "n1"
]
[
  "n2"
]

list settings.name

% cat sample.json | jq -r '.[].settings[].name'

setting1
setting2
setting1

list names & settings.name

% cat sample.json | jq -r '.[] | {name: .name, setting_name: .settings[].name}'

{
  "name": "n1",
  "setting_name": "setting1"
}
{
  "name": "n1",
  "setting_name": "setting2"
}
{
  "name": "n2",
  "setting_name": "setting1"
}

objects into arrays

% cat sample.json | jq -r '.[] | {name: .name, setting_name: .settings[].name} | [.name, .setting_name]'

[
  "n1",
  "setting1"
]
[
  "n1",
  "setting2"
]
[
  "n2",
  "setting1"
]

arrays to csv

% cat sample.json | jq -r '.[] | {name: .name, setting_name: .settings[].name} | [.name, .setting_name] | @csv'

"n1","setting1"
"n1","setting2"
"n2","setting1"