yq/pkg/yqlib/doc/Add.md

Add behaves differently according to the type of the LHS:

• arrays: concatenate
• number scalars: arithmetic addition (soon)
• string scalars: concatenate (soon)

Use += as append assign for things like increment. .a += .x is equivalent to running .a |= . + .x.

Concatenate and assign arrays

Given a sample.yml file of:

a:
  val: thing
  b:
    - cat
    - dog

then

yq eval '.a.b += ["cow"]' sample.yml

will output

a:
  val: thing
  b:
    - cat
    - dog
    - cow

Concatenate arrays

Given a sample.yml file of:

a:
  - 1
  - 2
b:
  - 3
  - 4

then

yq eval '.a + .b' sample.yml

will output

- 1
- 2
- 3
- 4

Concatenate null to array

Given a sample.yml file of:

a:
  - 1
  - 2

then

yq eval '.a + null' sample.yml

will output

- 1
- 2

Add object to array

Given a sample.yml file of:

a:
  - 1
  - 2
c:
  cat: meow

then

yq eval '.a + .c' sample.yml

will output

- 1
- 2
- cat: meow

Add string to array

Given a sample.yml file of:

a:
  - 1
  - 2

then

yq eval '.a + "hello"' sample.yml

will output

- 1
- 2
- hello

Update array (append)

Given a sample.yml file of:

a:
  - 1
  - 2
b:
  - 3
  - 4

then

yq eval '.a = .a + .b' sample.yml

will output

a:
  - 1
  - 2
  - 3
  - 4
b:
  - 3
  - 4