JQ – Cheatsheet

by Ralph Allgemein

Inhaltsverzeichnis

Installing jq

On Mac OS

brew install jq

Useful arguments

When running jq, the following arguments may become handy:

ArgumentDescription
--versionOutput the jq version and exit with zero.
--sort-keysOutput the fields of each object with the keys in sorted order.

Basic concepts

The syntax for jq is pretty coherent:

SyntaxDescription
,Filters separated by a comma will produce multiple independent outputs
?Will ignores error if the type is unexpected
[]Array construction
{}Object construction
+Concatenate or Add
–Difference of sets or Substract
lengthSize of selected element
|Pipes are used to chain commands in a similar fashion than bash

Dealing with json objects

DescriptionCommand
Display all keysjq 'keys'
Adds + 1 to all itemsjq 'map_values(.+1)'
Delete a keyjq 'del(.foo)'
Convert an object to arrayto_entries | map([.key, .value])

Dealing with fields

DescriptionCommand
Concatenate two fieldsfieldNew=.field1+' '+.field2

Dealing with json arrays

Slicing and Filtering

DescriptionCommand
Alljq .[]
Firstjq '.[0]'
Rangejq '.[2:4]'
First 3jq '.[:3]'
Last 2jq '.[-2:]'
Before Lastjq '.[-2]'
Select array of int by valuejq 'map(select(. >= 2))'
Select array of objects by value** jq ‘.[] | select(.id == “second”)’**
Select by type** jq ‘.[] | numbers’ ** with type been arrays, objects, iterables, booleans, numbers, normals, finites, strings, nulls, values, scalars

Mapping and Transforming

DescriptionCommand
Add + 1 to all itemsjq 'map(.+1)'
Delete 2 itemsjq 'del(.[1, 2])'
Concatenate arraysjq 'add'
Flatten an arrayjq 'flatten'
Create a range of numbersjq '[range(2;4)]'
Display the type of each itemjq 'map(type)'
Sort an array of basic typejq 'sort'
Sort an array of objectsjq 'sort_by(.foo)'
Group by a key – opposite to flattenjq 'group_by(.foo)'
Minimun value of an arrayjq 'min' .See also min, max, min_by(path_exp), max_by(path_exp)
Remove duplicatesjq 'unique' or jq 'unique_by(.foo)' or jq 'unique_by(length)'
Reverse an arrayjq 'reverse'