如何筛选OPNSense防火墙VLAN配置中selected=1的子属性？

假设你的原始JSON结构类似这样：

{
  "vlans": [
    {
      "if": "em0",
      "pcp": [
        {"value": 0, "selected": 0},
        {"value": 3, "selected": 1}
      ],
      "proto": [
        {"value": "802.1Q", "selected": 1},
        {"value": "802.1ad", "selected": 0}
      ],
      "description": "要移除的字段"
    },
    {
      "if": "em1",
      "pcp": [{"value": 5, "selected": 1}],
      "proto": [{"value": "802.1ad", "selected": 0}],
      "other": "无用字段"
    }
  ]
}

要保留if字段，以及pcp、proto数组中selected等于1的子元素，用以下jq命令：

jq '.vlans |= map({
  if: .if,
  pcp: (.pcp | map(select(.selected == 1))),
  proto: (.proto | map(select(.selected == 1)))
})' input.json > output.json

执行后得到的精简结果：

{
  "vlans": [
    {
      "if": "em0",
      "pcp": [{"value": 3, "selected": 1}],
      "proto": [{"value": "802.1Q", "selected": 1}]
    },
    {
      "if": "em1",
      "pcp": [{"value": 5, "selected": 1}],
      "proto": []
    }
  ]
}

如果希望过滤后子数组为空时自动移除该字段，用进阶版命令：

jq '.vlans |= map(
  .if as $if
  | (.pcp | map(select(.selected == 1))) as $pcp
  | (.proto | map(select(.selected == 1))) as $proto
  | {}
  | .if = $if
  | if $pcp != [] then .pcp = $pcp else . end
  | if $proto != [] then .proto = $proto else . end
)' input.json > output.json

此时第二个VLAN的proto字段会被移除，结果如下：

{
  "vlans": [
    {
      "if": "em0",
      "pcp": [{"value": 3, "selected": 1}],
      "proto": [{"value": "802.1Q", "selected": 1}]
    },
    {
      "if": "em1",
      "pcp": [{"value": 5, "selected": 1}]
    }
  ]
}

核心逻辑说明：

• map(...) 遍历每个VLAN对象，生成新的对象结构
• select(.selected == 1) 筛选子属性中符合条件的元素
• map(select(...)) 对数组整体过滤，保留符合条件的元素
• 进阶版通过变量缓存过滤结果，再根据是否为空决定是否保留字段

内容的提问来源于stack exchange，提问作者NorbertK