How can I get the names of all namespaces containing the word "nginx" and store those name-CodePudding

Basically I want to automate this task where I have some namespaces in Kubernetes I need to delete and others that I want to leave alone. These namespaces contain the word nginx. So I was thinking in order to do that I could get the output of get namespace using some regex and store those namespaces in an array, then iterate through that array deleting them one by one.

array=($(kubectl get ns | jq -r 'keys[]'))
declare -p array
for n in {array};
do
    kubectl delete $n
done

I tried doing something like this but this is very basic and doesn't even have the regex. But I just left it here as an example to show what I'm trying to achieve. Any help is appreciated and thanks in advance.

CodePudding user response：

kubectl get ns doesn't output JSON unless you add -o json. This:

array=($(kubectl get ns | jq -r 'keys[]'))

Should result in an error like:

parse error: Invalid numeric literal at line 1, column 5

kubectl get ns -o json emits a JSON response that contains a list of Namespace resources in the items key. You need to get the metadata.name attribute from each item, so:

kubectl get ns -o json | jq -r  '.items[].metadata.name'

You only want namespaces that contain the word "nginx". We could filter the above list with grep, or we could add that condition to our jq expression:

kubectl get ns -o json | jq -r  '.items[]|select(.metadata.name|test("nginx"))|.metadata.name'

This will output your desired namespaces. At this point, there's no reason to store this in array and use a for loop; you can just pipe the output to xargs:

kubectl get ns -o json |
jq -r  '.items[]|select(.metadata.name|test("nginx"))|.metadata.name' |
xargs kubectl delete ns

CodePudding user response：

kubectl get ns

output

NAME                          STATUS        AGE
default                       Active        75d
kube-public                   Active        75d
kube-system                   Active        75d
oci-service-operator-system   Active        31d
olm                           Active        31d

command

kubectl get ns --no-headers |  awk '{if ($1 ~ "de") print $1}'

Output

default
kube-node-lease

this will give you a list of namespaces

array=$(kubectl get ns --no-headers |  awk '{if ($1 ~ "de") print $1}')

Testing

bash-4.2$ array=$(kubectl get ns --no-headers |  awk '{if ($1 ~ "de") print $1}')
bash-4.2$ echo $array
default kube-node-lease
bash-4.2$ for n in $array; do echo $n; done
default
kube-node-lease
bash-4.2$