jq: select

Official Documentation

missing array fields

Similar to something like javascript optional chaining , the select operator can work on array fields that might or might not exist.

Input: '{"x": {"y": [1,2,3], "z": [4,5]}}'

jq '.x.y[]'

Output: 1

2

3

jq '.x.a[]'

Output: jq: error (at <stdin>:1): Cannot iterate over null (null)

Using select to deal with missing fields.

Input: '{"x": {"y": [1,2,3], "z": [4,5]}}'

jq '.x|select(.y).y[]'

Output: 1

2

3

jq '.x|select(.a).a[]'

Output:

The alternative operator can be used in this example as well. Not sure which ends up being more readable.

Input: '{"x": {"y": [1,2,3], "z": [4,5]}}'

jq '.x|(.y//[])[]'

Output: 1

2

3

jq '.x|(.a//[])[]'

Output: