JQ cheatsheet

JQ is a lightweight and flexible command-line JSON processor. This is a cheatsheet of commands and function that I’ve found useful for quick reference.

You can get full JQ Cheat Sheet Here.

Common usages

Here are some common ways jq is utilized.

Piping from curl

# get the Astronomy Picture of the Day (APOD) curl -s api.nasa.gov/planetary/apod?api_key=DEMO_KEY | jq (Note that piping to jq with no jq script will just format and colorize the JSON. Nice!)

From a JSON file

Just pass the file path after the jq script.

jq '.name' package.json 

In a chain of pipes

You’ll probably want to use the -r (raw) command if you’re using it in a pipeline or saving the output to a variable. -r gets rid of formatting like quotes and spaces for single values. For objects, it outputs valid JSON so it will have quotes.

# this downloads the latest APOD and saves to a file url="https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY" curl -o apod.png "$(curl -s $url | jq -r '.hdurl')" 

Common selectors

Get a named property

echo '{"id": 1, "name": "Cam"}' | jq '.id'`` # 1 

echo '{"nested": {"a": {"b": 42}}}' | jq '.nested.a.b' # 42 

Get an array element by index

echo '[0, 1, 1, 2, 3, 5, 8]' | jq '.[3]' # 3 

Get an array element’s property

echo '[{"id": 1, "name": "Mario"}, {"id": 2, "name": "Luigi"}]' | jq '.[1].name' # Luigi 

Slice an array

Slices an array on by index.

echo '["a", "b", "c", "d"]' | jq '.[1:3]' # ["b", "c"] 

Either the first or last index can be omitted to go from the begining or end.

echo '["a", "b", "c", "d"]' | jq '.[1:]' # ["b", "c", "d"] 

Creating a new object

The syntax looks like this: { myPropertyName: .propertyFromJSON }

echo '{ "a": 1, "b": 2 }' | jq '{ a: .b, b: .a }'
# { "a": 2, "b": 1 }