JQ

[aibangjuxin]

Here are some examples of more advanced usage of jq:

Recursive Descent

Suppose you have a JSON file data.json containing a nested object:

{
  "name": "John",
  "address": {
    "street": "123 Main St",
    "city": "Anytown",
    "state": "CA",
    "zip": "12345"
  },
  "friends": [
    {
      "name": "Jane",
      "age": 25
    },
    {
      "name": "Bob",
      "age": 30
    }
  ]
}

You can use jq to recursively traverse the object and extract specific values:

jq '.. | .name?' data.json

This will output:

"John"
"Jane"
"Bob"

The .. syntax tells jq to recursively traverse the object, and the .name? syntax extracts the value of the name property if it exists.

Aggregating Data

Suppose you have a JSON file data.json containing an array of objects:

[
  {
    "name": "John",
    "age": 30
  },
  {
    "name": "Jane",
    "age": 25
  },
  {
    "name": "Bob",
    "age": 40
  }
]

You can use jq to calculate the average age:

jq 'add | . / length' data.json

This will output:

31.666666666666668

The add function sums up the values, and the length function returns the length of the array. The / operator performs division.

Grouping and Sorting

Suppose you have a JSON file data.json containing an array of objects:

[
  {
    "name": "John",
    "department": "Sales",
    "salary": 50000
  },
  {
    "name": "Jane",
    "department": "Marketing",
    "salary": 60000
  },
  {
    "name": "Bob",
    "department": "Sales",
    "salary": 70000
  }
]

You can use jq to group the data by department and calculate the total salary for each department:

jq 'group_by(.department) | .[] | { department: .[0].department, total_salary: (map(.salary) | add) }' data.json

This will output:

[
  {
    "department": "Marketing",
    "total_salary": 60000
  },
  {
    "department": "Sales",
    "total_salary": 120000
  }
]

The group_by function groups the data by department, and the map function extracts the salaries for each group. The add function sums up the salaries.

Merging Data

Suppose you have two JSON files, data1.json and data2.json, containing arrays of objects:

// data1.json
[
  {
    "name": "John",
    "age": 30
  },
  {
    "name": "Jane",
    "age": 25
  }
]

// data2.json
[
  {
    "name": "John",
    " occupation": "Developer"
  },
  {
    "name": "Jane",
    " occupation": "Designer"
  }
]

You can use jq to merge the two files based on the name property:

jq -s 'map({name, age, occupation}) | group_by(.name) | .[] | { name: .[0].name, age: .[0].age, occupation: .[1].occupation }' data1.json data2.json

This will output:

[
  {
    "name": "John",
    "age": 30,
    "occupation": "Developer"
  },
  {
    "name": "Jane",
    "age": 25,
    "occupation": "Designer"
  }
]

The -s option tells jq to read the input files sequentially, and the group_by function merges the data based on the name property.

These are just a few examples of the many advanced things you can do with jq. I hope this helps!

[aibangjuxin]

jq 是一个轻量级且强大的命令行JSON处理器，它允许你通过编写类似于域名的查询语法来处理JSON数据。以下是一些使用 jq 进行高级过滤的示例：

1. 选择特定字段：

   jq '.fieldName'

2. 选择所有字段：

   jq '.'

3. 选择多个特定字段：

   jq '.fieldName1, .fieldName2'

4. 过滤数组中的对象：

   jq '.arrayField[] | select(.fieldName == "value")'

5. 使用正则表达式过滤字段值：

   jq --arg regex '.*your_regex.*' '.arrayField[] | select(.fieldName | test($regex))'

6. 获取数组中第一个元素：

   jq '.arrayField[0]'

7. 获取数组中最后一个元素：

   jq '.arrayField[-1]'

8. 计算数组中元素的数量：

   jq '.arrayField | length'

9. 计算数组中满足条件的元素数量：

   jq '.arrayField | length | select(. > 0)'

10. 对数组中的元素进行排序：

    jq '.arrayField | sort_by(.fieldName)'

11. 对数组中的元素进行逆序：

    jq '.arrayField | reverse'

12. 从嵌套的JSON结构中提取信息：

    jq '.parentField[].childField'

13. 使用条件表达式：

    jq '.arrayField[] | if .fieldName == "value" then . else empty end'

14. 创建新的JSON结构：

    jq '[ .arrayField[] | {newField: .fieldName} ]'

15. 合并多个JSON文件：

    jq -s '.[]' file1.json file2.json > merged.json

16. 递归查询所有匹配的字段：

    jq 'recurse(.[]; .fieldName?)'

17. 使用变量：

    jq --arg name "value" '. | select(.fieldName == $name)'

18. 格式化JSON输出：

    jq '.'

19. 计算字段的总和：

    jq '.arrayField | add'

20. 将JSON对象转换为键值对数组：

    jq 'to_entries | .[] | .key as $k | .value as $v | "\($k): \($v)"'

这些示例展示了 jq 的一些强大功能，但 jq 的能力远不止这些。根据你的具体需求，你可以编写更复杂的查询来处理JSON数据。记得在使用 jq 之前，你需要安装它。在大多数Linux发行版中，你可以使用包管理器来安装。