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Merge

Yaml files can be merged using the 'merge' command. Each additional file merged with the first file will set values for any key not existing already or where the key has no value.

yq m <yaml_file|json_file> <path>...

This command can take a json file as input too, and will output yaml unless specified to export as json (-j)

To Stdout

Given a data1.yaml file of:

a: simple
b: [1, 2]

and data2.yaml file of:

a: other
c:
  test: 1

then

yq m data1.yaml data2.yaml

will output:

a: simple
b: [1, 2]
c:
  test: 1

Updating files in-place

Given a data1.yaml file of:

a: simple
b: [1, 2]

and data2.yaml file of:

a: other
c:
  test: 1

then

yq m -i data1.yaml data2.yaml

will update the data1.yaml file so that the value of 'c' is 'test: 1'.

Overwrite values

Given a data1.yaml file of:

a: simple
b: [1, 2]

and data2.yaml file of:

a: other
c:
  test: 1

then

yq m -x data1.yaml data2.yaml

will output:

a: other
b: [1, 2]
c:
  test: 1

Overwrite values with arrays

Given a data1.yaml file of:

a: simple
b: [1, 2]

and data3.yaml file of:

b: [2, 3, 4]
c:
  test: 2
  other: true
d: false

then

yq m -x data1.yaml data3.yaml

will output:

a: simple
b: [2, 3, 4]
c:
  test: 2
  other: true
d: false

Notice that 'b' does not result in the merging of the values within an array. The underlying library does not currently handle merging values within an array.