Shell Functions

The following shell functions are often quite useful for debugging. You can add them to your ~/.bashrc or ~/.zshrc at your pleasure.

You don’t have to use them, but it’s helpful to know what they are, since folks tend to use them as abbreviations in messaging.

Just as typing kubectl get pod is kind of tedious to type on the cli, (k get pod or even just pods is much faster), typing that as instructions to someone looking for help is likewise faster and less error prone.

Plus, once you start using the funcs, you start having trouble remembering the full command syntax. Don’t even get me started on kubectl config get-contexts. Install the functions and just type context, get the info you’re after, and get on with your day.

Nik’s Shell Functions

• niks-k8s-shell-funcs.sh

Contents:

    # called without arguments, displays context and current context
    # called with an argument, changes into the context given
    function context {
      if [ -n "$1" ]; then
        kubectl config use-context $1
      else
        kubectl config get-contexts
      fi
    }

    # Do you want to type 'kubectl' all the time?
    alias k=kubectl

    # Typing 'kubectl get pod' gets old, too
    alias pods="kubectl get pod"

    # get logs from a pod matching a pattern in the current namespace, or another
    function podlogs {
      PATTERN=$1
      NS=$2
      if [ -n "$NS" ]; then
        clear && k logs -n $NS -f $(pods -n $NS | grep ${PATTERN} | cut -d " " -f 1)
      else
        clear && k logs -f $(pods | grep ${PATTERN} | cut -d " " -f 1)
      fi
    }

    # delete a pod matching a pattern in the current namespace or another
    function delpod {
      PATTERN=$1
      NS=$2
      if [ -n "$NS" ]; then
        PODS=$(pods -n $NS | grep ${PATTERN} | cut -d " " -f 1)
        echo "${PODS}" | xargs kubectl delete pod -n $NS
      else
        PODS=$(pods | grep ${PATTERN} | cut -d " " -f 1)
        echo "${PODS}" | xargs kubectl delete pod
      fi
    }

    # describe a pod matching a pattern in the current namespace or another
    function descpod {
      PATTERN=$1
      NS=$2
      if [ -n "$NS" ]; then
        PODS=$(pods -n $NS | grep ${PATTERN} | cut -d " " -f 1)
        echo "${PODS}" | xargs kubectl describe pod -n $NS
      else
        PODS=$(pods | grep ${PATTERN} | cut -d " " -f 1)
        echo "${PODS}" | xargs kubectl describe pod
      fi
    }

    # show images in use in a namespace, or globally
    function images {
      NS=$1

      if [[ -z "$NS" ]]; then
        kubectl get pods --all-namespaces -o jsonpath="{.items[*].spec['initContainers', 'containers'][*].image}" |tr -s '[[:space:]]' '\n' |sort |uniq -c

      else
        kubectl get pods -n "${NS}" -o jsonpath="{.items[*].spec['initContainers', 'containers'][*].image}" |tr -s '[[:space:]]' '\n' |sort |uniq -c

      fi
    }
        
    # Delete Failed Jobs in a Namespace
    function delfailedjobs {
      NS=$1
      if [ -z "$NS" ]; then
        echo "Usage: delfailedjobs <namespace>"
      else
        echo "Deleting failed jobs in $NS"
      fi

      kubectl get pods -n ${NS} --field-selector 'status.phase=Failed' -o name | xargs kubectl delete -n ${NS}
    }

    # Decode JWT's
    function decjwt {
        jq -R 'split(".") |.[0:2] | map(@base64d) | map(fromjson)'
    }

    # Get a JWT out of a K8S Cluster
    function gettoken {
      POD_PATTERN=$1
      TOKEN_DOMAIN=$2
      kubectl exec $(kubectl get pod | grep $POD_PATTERN | awk '{print $1}') -- cat /var/run/secrets/${TOKEN_DOMAIN}/serviceaccount/token

    }

    # Pull the generated Prometheus Config out of a Prometheus instance created by Prometheus Operator.
    alias promconfig="kubectl get secret -n monitoring prometheus-k8s -o json | jq -r .data.\\\"prometheus.yaml.gz\\\" | base64 -d | gunzip | vim -R -"