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Multiply (Merge)

Multiply (Merge)

Like the multiple operator in jq, depending on the operands, this multiply operator will do different things. Currently numbers, arrays and objects are supported.

Objects and arrays - merging

Objects are merged deeply matching on matching keys. By default, array values override and are not deeply merged.
Note that when merging objects, this operator returns the merged object (not the parent). This will be clearer in the examples below.

Merge Flags

You can control how objects are merged by using one or more of the following flags. Multiple flags can be used together, e.g. .a *+? .b. See examples below
  • + append arrays
  • d deeply merge arrays
  • ? only merge existing fields
  • n only merge new fields
  • c clobber custom tags

Merge two files together

This uses the load operator to merge file2 into file1.
yq '. *= load("file2.yml")' file1.yml

Merging all files

Note the use of eval-all to ensure all documents are loaded into memory.
yq eval-all '. as $item ireduce ({}; . * $item )' *.yml

Merging complex arrays together by a key field

By default - yq merge is naive. It merges maps when they match the key name, and arrays are merged either by appending them together, or merging the entries by their position in the array.
For more complex array merging (e.g. merging items that match on a certain key) please see the example here
Note that versions prior to 4.18 require the 'eval/e' command to be specified.
yq e <exp> <file>

Multiply integers

Given a sample.yml file of:
a: 3
b: 4
then
yq '.a *= .b' sample.yml
will output
a: 12
b: 4

Merge objects together, returning merged result only

Given a sample.yml file of:
a:
field: me
fieldA: cat
b:
field:
g: wizz
fieldB: dog
then
yq '.a * .b' sample.yml
will output
field:
g: wizz
fieldA: cat
fieldB: dog

Merge objects together, returning parent object

Given a sample.yml file of:
a:
field: me
fieldA: cat
b:
field:
g: wizz
fieldB: dog
then
yq '. * {"a":.b}' sample.yml
will output
a:
field:
g: wizz
fieldA: cat
fieldB: dog
b:
field:
g: wizz
fieldB: dog

Merge keeps style of LHS

Given a sample.yml file of:
a: {things: great}
b:
also: "me"
then
yq '. * {"a":.b}' sample.yml
will output
a: {things: great, also: "me"}
b:
also: "me"

Merge arrays

Given a sample.yml file of:
a:
- 1
- 2
- 3
b:
- 3
- 4
- 5
then
yq '. * {"a":.b}' sample.yml
will output
a:
- 3
- 4
- 5
b:
- 3
- 4
- 5

Merge, only existing fields

Given a sample.yml file of:
a:
thing: one
cat: frog
b:
missing: two
thing: two
then
yq '.a *? .b' sample.yml
will output
thing: two
cat: frog

Merge, only new fields

Given a sample.yml file of:
a:
thing: one
cat: frog
b:
missing: two
thing: two
then
yq '.a *n .b' sample.yml
will output
thing: one
cat: frog
missing: two

Merge, appending arrays

Given a sample.yml file of:
a:
array:
- 1
- 2
- animal: dog
value: coconut
b:
array:
- 3
- 4
- animal: cat
value: banana
then
yq '.a *+ .b' sample.yml
will output
array:
- 1
- 2
- animal: dog
- 3
- 4
- animal: cat
value: banana

Merge, only existing fields, appending arrays

Given a sample.yml file of:
a:
thing:
- 1
- 2
b:
thing:
- 3
- 4
another:
- 1
then
yq '.a *?+ .b' sample.yml
will output
thing:
- 1
- 2
- 3
- 4

Merge, deeply merging arrays

Merging arrays deeply means arrays are merge like objects, with indexes as their key. In this case, we merge the first item in the array, and do nothing with the second.
Given a sample.yml file of:
a:
- name: fred
age: 12
- name: bob
age: 32
b:
- name: fred
age: 34
then
yq '.a *d .b' sample.yml
will output
- name: fred
age: 34
- name: bob
age: 32

Merge arrays of objects together, matching on a key

This is a fairly complex expression - you can use it as is by providing the environment variables as seen in the example below.
It merges in the array provided in the second file into the first - matching on equal keys.
Explanation:
The approach, at a high level, is to reduce into a merged map (keyed by the unique key) and then convert that back into an array.
First the expression will create a map from the arrays keyed by the idPath, the unique field we want to merge by. The reduce operator is merging '({}; . * $item )', so array elements with the matching key will be merged together.
Next, we convert the map back to an array, using reduce again, concatenating all the map values together.
Finally, we set the result of the merged array back into the first doc.
Thanks Kev from stackoverflow
Given a sample.yml file of:
myArray:
- a: apple
b: appleB
- a: kiwi
b: kiwiB
- a: banana
b: bananaB
something: else
And another sample another.yml file of:
newArray:
- a: banana
c: bananaC
- a: apple
b: appleB2
- a: dingo
c: dingoC
then
idPath=".a" originalPath=".myArray" otherPath=".newArray" yq eval-all '
(
(( (eval(strenv(originalPath)) + eval(strenv(otherPath))) | .[] | {(eval(strenv(idPath))): .}) as $item ireduce ({}; . * $item )) as $uniqueMap
| ( $uniqueMap | to_entries | .[]) as $item ireduce([]; . + $item.value)
) as $mergedArray
| select(fi == 0) | (eval(strenv(originalPath))) = $mergedArray
' sample.yml another.yml
will output
myArray:
- a: apple
b: appleB2
- a: kiwi
b: kiwiB
- a: banana
b: bananaB
c: bananaC
- a: dingo
c: dingoC
something: else

Merge to prefix an element

Given a sample.yml file of:
a: cat
b: dog
then
yq '. * {"a": {"c": .a}}' sample.yml
will output
a:
c: cat
b: dog

Merge with simple aliases

Given a sample.yml file of:
a: &cat
c: frog
b:
f: *cat
c:
g: thongs
then
yq '.c * .b' sample.yml
will output
g: thongs
f: *cat

Merge copies anchor names

Given a sample.yml file of:
a:
c: &cat frog
b:
f: *cat
c:
g: thongs
then
yq '.c * .a' sample.yml
will output
g: thongs
c: &cat frog

Merge with merge anchors

Given a sample.yml file of:
foo: &foo
a: foo_a
thing: foo_thing
c: foo_c
bar: &bar
b: bar_b
thing: bar_thing
c: bar_c
foobarList:
b: foobarList_b
!!merge <<:
- *foo
- *bar
c: foobarList_c
foobar:
c: foobar_c
!!merge <<: *foo
thing: foobar_thing
then
yq '.foobar * .foobarList' sample.yml
will output
c: foobarList_c
!!merge <<:
- *foo
- *bar
thing: foobar_thing
b: foobarList_b

Custom types: that are really numbers

When custom tags are encountered, yq will try to decode the underlying type.
Given a sample.yml file of:
a: !horse 2
b: !goat 3
then
yq '.a = .a * .b' sample.yml
will output
a: !horse 6
b: !goat 3

Custom types: that are really maps

Custom tags will be maintained.
Given a sample.yml file of:
a: !horse
cat: meow
b: !goat
dog: woof
then
yq '.a = .a * .b' sample.yml
will output
a: !horse
cat: meow
dog: woof
b: !goat
dog: woof

Custom types: clobber tags

Use the c option to clobber custom tags. Note that the second tag is now used
Given a sample.yml file of:
a: !horse
cat: meow
b: !goat
dog: woof
then
yq '.a *=c .b' sample.yml
will output
a: !goat
cat: meow
dog: woof
b: !goat
dog: woof
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On this page
Multiply (Merge)
Objects and arrays - merging
Merging complex arrays together by a key field
Multiply integers
Merge objects together, returning merged result only
Merge objects together, returning parent object
Merge keeps style of LHS
Merge arrays
Merge, only existing fields
Merge, only new fields
Merge, appending arrays
Merge, only existing fields, appending arrays
Merge, deeply merging arrays
Merge arrays of objects together, matching on a key
Merge to prefix an element
Merge with simple aliases
Merge copies anchor names
Merge with merge anchors
Custom types: that are really numbers
Custom types: that are really maps
Custom types: clobber tags