jq Cheat Sheet

jq_cheat_sheet.adoc

jq Cheat Sheet

jq is useful utility, but I use it infrequently and each time I have to check what was the filters syntax. This cheat sheet helps we to recall what is the expression that I need. Hopefully it would help others too. For full guide refer to the official jq manual.

All the jq you (usually) need

Given the following JSON:

{
  "menus": {
    "File": {
      "enabled": true,
      "menu_items": [
        { "label": "New", "enabled": true },
        { "label": "Open...", "enabled": true },
        { "label": "Print...", "enabled": false },
        { "label": "Exit", "enabled": true }
      ]
    },
    "Edit": {
      "enabled": false,
      "menu_items": [
        { "label": "Copy", "enabled": false },
        { "label": "Cut", "enabled": false },
        { "label": "Paste", "enabled": true }
      ]
    }
  }
}

The following script will select the labels of all enabled menu items which are nested within enabled menus:

jq --raw-output '.menus[] | select ( .enabled == true ) | .menu_items[] | select ( .enabled == true ) | .label'

The output is:

New
Open...
Exit

Get field value / array element

To navigate within object use dot (.). Single dot (.) means the object root.

echo '{ "foo": { "bar": 5 } }' | jq '.foo.bar'

# Output: 5

To access a single value in an array use square brackets ([]).

echo '[1,2,3]' | jq '.[0]'

# Output: 1

Get all array elements / object values

To get all elements of an array use square brackets without index:

echo '[1,2,3]' | jq '.[]'

# Output: 1 2 3

You can use the same syntax to get all values of object, ignoring the keys.

echo '{"foo": 3, "bar": 5 }' | jq '.[]'

# Output: 3 5

Chaining filters

Use pipe (|) to chain multiple filters.

echo '{ "foo": { "bar": 5 } }' | jq '.foo | .bar'

# Output: 5

Select elements

To select (filter) only elements that satisfy given condition use select.

echo '[1,2,3,4,5]' | jq '.[] | select( . > 2) | select( . < 5)'

# Output: 3 4

echo '[ { "value": 1 }, { "value": 2 } ]' | jq '.[] | select( .value > 1)'

# Output: { "value": 2 }

Raw output

By default jq returns JSON values. This means that if you select string value you will get quotes around it:

echo '{ "foo": "bar" }' | jq '.foo'

# Output: "bar"

If you want to use the values in Bash script it might be more convenient to get the raw values (without the quotes). Just use the --raw-output option:

echo '{ "foo": "bar" }' | jq --raw-output '.foo'

# Output: bar

What about YAML

Your data is in YAML format? No problems. Use yq instead. It will convert you YAML to JSON and then send it to jq.