yq/commands/write-update.md

description

description
Updates all the matching nodes of path expression in a yaml file to the supplied value.

Write

yq w <yaml_file> <path_expression> <new value>

See docs for path expression and value parsing for more details, including controlling quotes and tags.

Basic

Given a sample.yaml file of:

b:
  c: 2

then

yq w sample.yaml b.c cat

will output:

b:
  c: cat

Updating files in-place

yq w -i sample.yaml b.c cat

will update the sample.yaml file so that the value of 'c' is cat.

From STDIN

cat sample.yaml | yq w - b.c blah

Adding new fields

Any missing fields in the path will be created on the fly.

Given a sample.yaml file of:

b:
  c: 2

then

yq w sample.yaml b.d[+] "new thing"

will output:

b:
  c: cat
  d:
    - new thing

Appending value to an array field

Given a sample.yaml file of:

b:
  c: 2
  d:
    - new thing
    - foo thing

then

yq w sample.yaml "b.d[+]" "bar thing"

will output:

b:
  c: cat
  d:
    - new thing
    - foo thing
    - bar thing

Note that the path is in quotes to avoid the square brackets being interpreted by your shell.

Multiple Documents

Update a single document

Given a sample.yaml file of:

something: else
---
b:
  c: 2

then

yq w -d1 sample.yaml b.c 5

will output:

something: else
---
b:
  c: 5

Update all documents

Given a sample.yaml file of:

something: else
---
b:
  c: 2

then

yq w -d'*' sample.yaml b.c 5

will output:

something: else
b:
  c: 5
---
b:
  c: 5

Writing Anchors

The ---anchorName flag can be used to set the anchor name of a node

Given a sample document of:

commonStuff:
    flavour: vanilla

Then:

yq write sample.yaml commonStuff --anchorName=commonBits

Will yield

commonStuff: &commonBits
    flavour: vanilla

Writing Aliases

The --makeAlias flag can create or update a node to be an alias to an anchor.

Given a sample file of:

commonStuff: &commonBits
    flavour: vanilla

Then

yq write sample.yaml --makeAnchor foo commonBits

Will yield:

commonStuff: &commonBits
    flavour: vanilla
foo: *commonBits

Updating only styles/tags without affecting values

You can use the write command to update the quoting style of nodes, or their tags, without re-specifying the values. This is done by omitting the value argument:

Given a sample document:

a:
  c: things
  d: other things

Then

yq write sample.yaml --style=single a.*

Will yield:

a:
  c: 'things'
  d: 'other things'

Using a script file to update

Given a sample.yaml file of:

b:
  d: be gone
  c: 2
  e:
    - name: Billy Bob # comment over here

and a script update_instructions.yaml of:

- command: update 
  path: b.c
  value:
    #great 
    things: frog # wow!
- command: delete
  path: b.d

then

yq w -s update_instructions.yaml sample.yaml

will output:

b:
  c:
    #great
    things: frog # wow!
  e:
  - name: Billy Bob # comment over here

And, of course, you can pipe the instructions in using '-':

cat update_instructions.yaml | yq w -s - sample.yaml