jqの基本的な使い方

対象データ

sample.json

{"menu": {
  "id": "file",
  "value": "File",
  "popup": {
    "menuitem": [
      {"value": "New", "onclick": "CreateNewDoc()"},
      {"value": "Open", "onclick": "OpenDoc()"},
      {"value": "Close", "onclick": "CloseDoc()"}
    ]
  }
}}

※参照元: JSON Example

目的別コマンド例

全てを表示

$ cat sample.json | jq "."
{
  "menu": {
    "popup": {
      "menuitem": [
        {
          "onclick": "CreateNewDoc()",
          "value": "New"
        },
        {
          "onclick": "OpenDoc()",
          "value": "Open"
        },
        {
          "onclick": "CloseDoc()",
          "value": "Close"
        }
      ]
    },
    "value": "File",
    "id": "file"
  }
}

menuの中身表示

$ cat sample.json | jq ".menu"
{
  "popup": {
    "menuitem": [
      {
        "onclick": "CreateNewDoc()",
        "value": "New"
      },
      {
        "onclick": "OpenDoc()",
        "value": "Open"
      },
      {
        "onclick": "CloseDoc()",
        "value": "Close"
      }
    ]
  },
  "value": "File",
  "id": "file"
}

menuitemの0番目の中身表示

$ cat sample.json | jq ".menu.popup.menuitem[0]"
{
  "onclick": "CreateNewDoc()",
  "value": "New"
}

menuitemの0番目のvalueを表示

$ cat sample.json | jq ".menu.popup.menuitem[0].value"
"New"

menuitemの全ての要素のvalueを表示

$ cat sample.json | jq ".menu.popup.menuitem[].value"
"New"
"Open"
"Close"