{
  "id": "field-selector-basics",
  "title": "Filtering Resources with Field Selectors",
  "category": "Core Concepts",
  "difficulty": "Easy",
  "type": "task",
  "weight": 4,
  "description": "## Filtering Resources with Field Selectors\n\nField selectors let you filter Kubernetes resources by the **value of specific object fields** — similar to how label selectors work but targeting any field in the resource spec or status.\n\nCommon use cases:\n- Find all pods in a specific phase: `kubectl get pods --field-selector=status.phase=Running`\n- Find resources in a specific namespace: `kubectl get pods --field-selector=metadata.namespace=kube-system`\n\n**Your task:**\n\nSeveral pods have been created for you — some Running, some in a Failed state.\n\n1. Use a field selector to list only the **Running** pods and count them. Save the count to `/tmp/running-count.txt`\n2. Use a field selector to list all pods **not** in the `default` namespace (filter by `metadata.namespace!=default`)\n\n```bash\n# Count running pods:\nkubectl get pods --field-selector=status.phase=Running --no-headers | wc -l\n```",
  "hints": [
    {
      "title": "Field selector syntax",
      "body": "Use `--field-selector=field.path=value` to filter. Multiple conditions are comma-separated. Supported operators: `=`, `==`, `!=`.",
      "command": "kubectl get pods --field-selector=status.phase=Running"
    },
    {
      "title": "Save running pod count to a file",
      "body": "Pipe the result through wc -l and redirect to the file.",
      "command": "kubectl get pods --field-selector=status.phase=Running --no-headers | wc -l | tr -d ' ' > /tmp/running-count.txt"
    }
  ],
  "setup_commands": [
    {
      "command": "kubectl run alpha --image=nginx:alpine 2>/dev/null || true"
    },
    {
      "command": "kubectl run beta --image=nginx:alpine 2>/dev/null || true"
    },
    {
      "command": "kubectl run crash-pod --image=busybox:1.36 --restart=Never -- /bin/false 2>/dev/null || true"
    },
    {
      "command": "kubectl rollout status deployment/alpha --timeout=30s 2>/dev/null || true"
    }
  ],
  "validation": {
    "commands": [
      {
        "description": "File /tmp/running-count.txt exists and has a numeric value",
        "command": "cat /tmp/running-count.txt",
        "expected_output": "^[0-9]+$",
        "match": "regex"
      },
      {
        "description": "The saved count matches the actual number of Running pods",
        "command": "LIVE=$(kubectl get pods --field-selector=status.phase=Running --no-headers 2>/dev/null | wc -l | tr -d ' '); SAVED=$(cat /tmp/running-count.txt 2>/dev/null | tr -d ' '); [ \"$LIVE\" = \"$SAVED\" ] && echo 'match' || echo 'mismatch'",
        "expected_output": "match",
        "match": "exact"
      }
    ]
  },
  "default_namespace": "default",
  "teardown_commands": [
    {
      "command": "kubectl delete pod alpha beta crash-pod --ignore-not-found --grace-period=0 --force"
    },
    {
      "command": "rm -f /tmp/running-count.txt"
    }
  ]
}