# json

## 介紹
json是一種文件格式,全稱JavaScript Object Notation,它是來自 JavaScript,能夠給人閱讀的文本,通常用來作為傳輸數據的數據格式。
在程式中通常以object, record, struct, dictionary, hash table, keyed list, associative array表示
## 格式
以 { "左大括號" 開始，以 } "右大括號" 結束
每個名稱後都有 ： "冒號"
每個名稱／值都用 , "逗號" 分隔

### 例子

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 27,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    }
  ],
  "children": [],
  "spouse": null
}

為了更容易閱讀json，所以可以把它用樹表示
### 例子

# json-c

## 安裝方法

sudo apt install libjson-c-dev

## 終端機

編譯

gcc "fileName".c -ljson-c -o "fileName"

執行

./"fileName"

## visual studio code
開啟tasks.json 在args新增"-l"和"json-c"

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: gcc-9 建置使用中檔案",
            "command": "/usr/bin/gcc-9",
            "args": [
                "-g",
                "${file}",
                "-o",
                "${fileDirname}/${fileBasenameNoExtension}",
                "-l",
                "json-c"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "偵錯工具產生的工作。"
        }
    ],
    "version": "2.0.0"
}

## 語法
讀取json return
如果讀取文件失敗，則此函數返回 NULL

json_object *root = json_object_from_file(""fileName".json");

用一行印出整個json

printf("The json file:\n\n%s\n", json_object_to_json_string(root));

格式化印出json

printf("The json file:\n\n%s\n", json_object_to_json_string_ext(root, JSON_C_TO_STRING_PRETTY));