Variable Operators

For more complex scenarios, variables can be used to hold values of expression to be used in other expressions.
Single value variable
Given a sample.yml file of:
a: cat
then
yq eval '.a as $foo | $foo' sample.yml
will output
cat
Multi value variable
Given a sample.yml file of:
- cat
- dog
then
yq eval '.[] as $foo | $foo' sample.yml
will output
cat
dog
Using variables as a lookup
Example taken from jq​
Given a sample.yml file of:
"posts":
  - "title": Frist psot
    "author": anon
  - "title": A well-written article
    "author": person1
"realnames":
  "anon": Anonymous Coward
  "person1": Person McPherson
then
yq eval '.realnames as $names | .posts[] | {"title":.title, "author": $names[.author]}' sample.yml
will output
title: Frist psot
author: Anonymous Coward
title: A well-written article
author: Person McPherson
Union
Next - Usage
Output format
Last updated 3 weeks ago