How to display constant values using custom-columns format of kubectl? - kubectl

Question

I have multiple clusters and I want to check which ingresses do not specify explicit certificate. Right now I use the following command:
~$ k config get-contexts -o name | grep -E 'app(5|3)41.+-admin' | xargs -n1 -I {} kubectl --context {} get ingress -A -o 'custom-columns=NS:{.metadata.namespace},NAME:{.metadata.name},CERT:{.spec.tls.*.secretName}' | grep '<none>'
argocd argo-cd-argocd-server <none>
argocd argo-cd-argocd-server <none>
reference-app reference-app-netcore-ingress <none>
argocd argo-cd-argocd-server <none>
argocd argo-cd-argocd-server <none>
test-ingress my-nginx <none>
~$
I want to improve the output by including the context name, but I can't figure out how to modify the custom-columns format to do that.

Answer 1

The below command would Not yield the exact desired output, but it will be close. using jsonpath, it's possible:
kubectl config get-contexts -o name | xargs -n1 -I {} kubectl get ingress -A -o jsonpath="{range .items[*]}{} {.metadata.namespace} {.metadata.name} {.spec.tls.*.secretName}{'\n'}{end}" --context {}
If the exact output is needed, then the kubectl output needs to be looped in the bash loop. Example:
kubectl config get-contexts -o name | while read context; do k get ingress -A -o 'custom-columns=NS:{.metadata.namespace},NAME:{.metadata.name},CERT:{.spec.tls.*.secretName}' --context "$context" |awk -vcon="$context" 'NR==1{$0=$0FS"CONTEXT"}NR>1{$0=$0 FS con}1'; done |column -t
NS NAME CERT CONTEXT
default tls-example-ingress testsecret-tls kubernetes-admin-istio-demo.local#istio-demo.local
default tls-example-ingress1 testsecret-tls kubernetes-admin-istio-demo.local#istio-demo.local
default tls-example-ingress2 <none> kubernetes-admin-istio-demo.local#istio-demo.local
To perform post-processing around the header and context, the awk command was used. Here is some details about it:
Command:
awk -vcon="$context" 'NR==1{$0=$0FS"CONTEXT"}NR>1{$0=$0 FS con}1'; done |column -t
-vcon="$context": This is to create a variable called con inside awk to store the value of bash variable($context).
NR==1: Here NR is the record number(in this case line number) and $0 means record/line.
NR==1{$0=$0FS"CONTEXT"}: This means, on the 1st line, reset the line to itself followed by FS(default is space) followed by a string "CONTEXT".
Similarly, NR>1{$0=$0 FS con} means, from the 2nd line onwards, append the line with FS followed by con.
1 in the end is the tell awk to do the print.