Assign (Update)

This operator is used to update node values. It can be used in either the:
plain form: =
Which will set the LHS node values equal to the RHS node values. The RHS expression is run against the matching nodes in the pipeline.
relative form: |=
This will do a similar thing to the plain form, but the RHS expression is run with each LHS node as context. This is useful for updating values based on old values, e.g. increment.
Flags
c clobber custom tags
Create yaml file
Running
yq --null-input '.a.b = "cat" | .x = "frog"'
will output
a:
  b: cat
x: frog
Update node to be the child value
Given a sample.yml file of:
a:
  b:
    g: foof
then
yq '.a |= .b' sample.yml
will output
a:
  g: foof
Double elements in an array
Given a sample.yml file of:
- 1
- 2
- 3
then
yq '.[] |= . * 2' sample.yml
will output
- 2
- 4
- 6
Update node from another file
Note this will also work when the second file is a scalar (string/number)
Given a sample.yml file of:
a: apples
And another sample another.yml file of:
b: bob
then
yq eval-all 'select(fileIndex==0).a = select(fileIndex==1) | select(fileIndex==0)' sample.yml another.yml
will output
a:
  b: bob
Update node to be the sibling value
Given a sample.yml file of:
a:
  b: child
b: sibling
then
yq '.a = .b' sample.yml
will output
a: sibling
b: sibling
Updated multiple paths
Given a sample.yml file of:
a: fieldA
b: fieldB
c: fieldC
then
yq '(.a, .c) = "potato"' sample.yml
will output
a: potato
b: fieldB
c: potato
Update string value
Given a sample.yml file of:
a:
  b: apple
then
yq '.a.b = "frog"' sample.yml
will output
a:
  b: frog
Update string value via |=
Note there is no difference between = and |= when the RHS is a scalar
Given a sample.yml file of:
a:
  b: apple
then
yq '.a.b |= "frog"' sample.yml
will output
a:
  b: frog
Update deeply selected results
Note that the LHS is wrapped in brackets! This is to ensure we don't first filter out the yaml and then update the snippet.
Given a sample.yml file of:
a:
  b: apple
  c: cactus
then
yq '(.a[] | select(. == "apple")) = "frog"' sample.yml
will output
a:
  b: frog
  c: cactus
Update array values
Given a sample.yml file of:
- candy
- apple
- sandy
then
yq '(.[] | select(. == "*andy")) = "bogs"' sample.yml
will output
- bogs
- apple
- bogs
Update empty object
Given a sample.yml file of:
{}
then
yq '.a.b |= "bogs"' sample.yml
will output
a:
  b: bogs
Update node value that has an anchor
Anchor will remain
Given a sample.yml file of:
a: &cool cat
then
yq '.a = "dog"' sample.yml
will output
a: &cool dog
Update empty object and array
Given a sample.yml file of:
{}
then
yq '.a.b.[0] |= "bogs"' sample.yml
will output
a:
  b:
    - bogs
Custom types are maintained by default
Given a sample.yml file of:
a: !cat meow
b: !dog woof
then
yq '.a = .b' sample.yml
will output
a: !cat woof
b: !dog woof
Custom types: clobber
Use the c option to clobber custom tags
Given a sample.yml file of:
a: !cat meow
b: !dog woof
then
yq '.a =c .b' sample.yml
will output
a: !dog woof
b: !dog woof

Array to Map

Boolean Operators

Last modified 6mo ago

Assign (Update)

plain form: `=`

relative form: `|=`

Flags

Create yaml file

Update node to be the child value

Double elements in an array

Update node from another file

Update node to be the sibling value

Updated multiple paths

Update string value

Update string value via |=

Update deeply selected results

Update array values

Update empty object

Update node value that has an anchor

Update empty object and array

Custom types are maintained by default

Custom types: clobber