How to change a specific YAML value for only certain YAML objects with yq

Let's assume the following YAML file:

---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: Bucket
metadata:
  name: kratix
  namespace: flux-system
spec:
  interval: 10s
  provider: generic
  bucketName: kratix
  endpoint: a.b.c.d:31337
  insecure: true
  secretRef:
    name: minio-credentials
---
apiVersion: v1
kind: Secret
metadata:
  name: minio-credentials
  namespace: flux-system
type: Opaque
data:
  accesskey: asecretkey
  secretkey: asecretvalue
---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: kratix-worker-resources
  namespace: flux-system
spec:
  interval: 3s
  prune: true
  dependsOn:
    - name: kratix-worker-dependencies
  sourceRef:
    kind: Bucket
    name: kratix
  path: ./worker-1/resources
---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: kratix-worker-dependencies
  namespace: flux-system
spec:
  interval: 8s
  prune: true
  sourceRef:
    kind: Bucket
    name: kratix
  path: ./worker-1/dependencies

This is what I want to do:

Note: By yq, I mean the Mike Farah version.

For YAML that is kind=Kustomization, I want to be able to modify the value for the .spec.path item from ./worker-1/<whatever> to ./<new value>/<whatever>, using yq. Everything else in the file needs to be copied as-is into the end result.

I have almost zero experience using yq and although I've read the documentation and have tried various things, I have not been able to figure out how to do this. At this early stage, yq is rather confusing.

Please include which implementation of yq you are using. You can employ the sub filter for string replacement in both of them.

kislyuk/yq:

yq -y 'select(.kind == "Kustomization").spec.path |= sub("/worker-1/"; "/whatever/")'

# or parametrized:
yq -y --arg kind Kustomization --arg from worker-1 --arg to whatever \
  'select(.kind == $kind).spec.path |= sub("/\($from)/"; "/\($to)/")'

• This does not (re-)print the initial document separator ---. If you need it, add the --explicit-start flag.
• This requires jq v1.5 from 2015, or higher.

mikefarah/yq:

yq 'select(.kind == "Kustomization").spec.path |= sub("/worker-1/", "/whatever/")'

# or parametrized:
kind=Kustomization from=worker-1 to=whatever yq \
  'select(.kind == strenv(kind)).spec.path |= sub("/\(env(from))/", "/\(env(to))/")'

• String interpolation with \(…) was introduced with v4.43.1 in 2024. For older versions, change "/\(env(from))/" and "/\(env(to))/" to "/" + env(from) + "/" and "/" + env(to) + "/", respectively.
• Since v4.18.1 from 2022, the eval (or e) command is set as default. For older versions, provide it manually as a separate argument right before the filter.
• String substitution with sub was introduced with v4.7.0 in 2021. Older versions are very outdated, and should be updated.

Output:

---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: Bucket
metadata:
  name: kratix
  namespace: flux-system
spec:
  interval: 10s
  provider: generic
  bucketName: kratix
  endpoint: a.b.c.d:31337
  insecure: true
  secretRef:
    name: minio-credentials
---
apiVersion: v1
kind: Secret
metadata:
  name: minio-credentials
  namespace: flux-system
type: Opaque
data:
  accesskey: asecretkey
  secretkey: asecretvalue
---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: kratix-worker-resources
  namespace: flux-system
spec:
  interval: 3s
  prune: true
  dependsOn:
    - name: kratix-worker-dependencies
  sourceRef:
    kind: Bucket
    name: kratix
  path: ./whatever/resources
---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: kratix-worker-dependencies
  namespace: flux-system
spec:
  interval: 8s
  prune: true
  sourceRef:
    kind: Bucket
    name: kratix
  path: ./whatever/dependencies