kubessh

#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'

if [[ $# -ne 2 && $# -ne 3 ]]; then
	echo "Usage: $0 namespace pattern [container]"
	exit 1
fi

NS_PATTERN="$1"
PATTERN="$2"

NAMESPACE="$(kubectl get ns | grep "$NS_PATTERN" | awk '{print $1}' | sed -n 1p)"
POD_ID=$(kubectl -n "$NAMESPACE" get pods | grep "$PATTERN" | sed -n 1p | awk '{print $1}')

for SHELL in /bin/bash /bin/sh; do
	if [[ $# -eq 2 ]]; then
		kubectl exec -n "$NAMESPACE" -it "$POD_ID" -- "$SHELL" && break

	else # container defined
		CONTAINER_ID="$(kubectl -n "$NAMESPACE" get pod "$POD_ID" \
			-o jsonpath="{.spec.containers[*].name}" | tr ' ' $'\n' | grep "$3")"
		kubectl exec -n "$NAMESPACE" -it "$POD_ID" --container "$CONTAINER_ID" -- "$SHELL" && break
	fi
done