Add new element to JSON array with jq

By Thomas Taylor | | 1 minutes
Linux

Adding a new element to an existing JSON array can be completed using jq.

Add element to existing array of objects using jq

This is a generic projects.json file:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

{
	"projects": [
		{
			"id": 1,
			"version": "2.3.0"
		},
		{
			"id": 2,
			"version": "1.54.0"
		}
	]
}

Appending a new element to the array can be completed in two ways:

1. += []

1
2
3
4

cat projects.json | jq '.projects += [{
	"id": 3,
	"version": "5.4.1"
}]'

2. |=

1
2
3
4

jq '.projects[.projects | length] = {
	"id": 3,
	"version": "5.4.1"
}'

Output:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16

{
	"projects": [
		{
			"id": 1,
			"version": "2.3.0"
		},
		{
			"id": 2,
			"version": "1.54.0"
		},
		{
			"id": 3,
			"version": "5.4.1"
		}
	]
}

Add element to existing array of strings using jq

Similarly with strings:

1

echo '["id1"]' | jq '. += ["id2"]'

or

1

echo '["id1"]' | jq '.[. | length] = "id2"'

Output:

1
2
3
4

[
	"id1",
	"id2"
]