chore: quick notes on yq (in place) edit

content/posts/2024-04-14-quick-notes-on-yq-edit.md

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+---
+title:  "Quick notes on yq edit"
+date:   2024-04-14
+tags:
+  - programming
+  - helm
+---
+
+One of the best thing about kubernetes, and especially gitops, is that we can re-use the same definitely
+across many different environment and clusters via very simple yaml manipulation. Howver, it is also true
+that editing yaml en-masse is not fun and automation is highly desirable. Most people will eventually turn
+to `yq`, and at the same time be slightly stuck on the syntax. So I am just out here documenting a few
+of the most used commands in my normal work.
+
+To find all the clusters that is current set to image `1.0.0` for application `app`
+
+```shell
+yq 'select(.app.image.tag=="1.0.0")' | filename *.yaml
+```
+
+which tells us which file satisfies that condition. Sometime we may want to only find the image for applications
+that have been enabled.
+
+```shell
+yq 'select(.app.enabled==true and .app.image.tag=="1.0.0")' | filename *.yaml
+```
+
+Then if we want to do an in-place update of all the images to a mor up to date version on the yaml file
+
+```shell
+yq -i 'with(.app; select(. | .enabled==true and .image.tag="1.0.0") | .image.tag="2.0.0")' *.yaml
+```
+
+But there are cases where the yaml have not been properly formatted before so the minor change turns out to be way
+bigger than expected. In those cases we can generate the diff on those selected changes by first formatting the
+yaml - wrapped in the following shell function `yq_edit` (which I am sure you would have encountered before
+in some shape or form if you live on github)
+
+```shell
+function yq_edit() {
+  yq eval --exit-status '.' "$2" | tee out1.yaml
+  yq eval --exit-status "$1" "$2" | tee out.yaml
+  diff -u out1.yaml out2.yaml | tee out.patch
+  patch "$2" < out.patch
+  rm out1.yaml out2.yaml out.patch "$2.orig"
+}
+```
+
+which allows us to perform updates easily via
+
+```shell
+yq_edit 'with(.app; select(.image.tag="1.0.0") | .image.tag="2.0.0")' *.yaml
+```