jq komutu - JSON processor

Giriş

Açıklaması şöyle

... jq is a command-line tool for parsing and manipulating JSON data. It is written in C and has a lightweight, minimalistic and flexible syntax. It allows you to filter, extract, and transform JSON data quickly and easily, making it a powerful tool for data processing and analysis.

jq was created by Steve Kemp. He started working on jq in early 2011, and the first version was released in April of that year. The tool quickly gained popularity among developers and data analysts, and it has since become one of the most widely used command-line JSON processors.

jq Filters

Açıklaması şöyle

jq reads JSON data from input and applies a series of filters to it, producing one or more outputs. The filters are written in a domain-specific language (DSL) that is similar to the one used in functional programming languages like Haskell, Lisp and Ruby.

Açıklaması şöyle

jq supports a wide range of filter types that can be used to select, extract, and modify JSON data, common ones are:

Selectors: Select specific parts of JSON data.

Functions: Built-in functions that can be used to perform various operations on the input JSON data.

Operators: Used to perform mathematical, logical, and comparison operations on the input JSON data.

Pipe: Used to connect multiple filters together, where the output of one filter is passed as input to the next filter.

jq Data Types

Açıklaması şöyle

jq supports several types of data, including:

Numbers: Integers and floating-point values, such as 42, 3.14, and -2.

Strings: Text enclosed in double quotes, such as “hello world”.

Booleans: true and false.

Arrays: Lists of values enclosed in square brackets, such as [1, 2, 3].

Objects: Key-value pairs enclosed in curly braces, such as {“name”: “Tony”, “age”: 100}.

Null: The special value null.

jq Regular Expression

Açıklaması şöyle

jq uses the Oniguruma regular expression library, as do php, ruby, TextMate, Sublime Text, etc, so the description here will focus on jq specifics.

The jq regex filters are defined so that they can be used using one of these patterns:

STRING | FILTER( REGEX )

STRING | FILTER( REGEX; FLAGS )

STRING | FILTER( [REGEX] )

STRING | FILTER( [REGEX, FLAGS] )

Örnek

Şöyle yaparız

$ cat file.json | jq '.[] | select(.email | test("^[a-z]+@"))'

$ cat file.json | jq '.[] | select(.email | test("^[a-z]+@") | not)'

Örnek

Pretty print için şöyle yaparız

kubectl get 
  --raw "..." 
  | jq .

Örnek

Şöyle yaparız

$ echo '{"name": "Tony", "age": 100}' | jq .
{
  "name": "Tony",
  "age": 100
}

Identifier Yani Key

Örnek

Şöyle yaparız

$ echo '{"foo": 42, "bar": "less interesting data"}'  | jq '.foo'
42

İsimli Array

Örnek

Elimizde şöyle bir JSON olsun

{
  "DBClusterSnapshots": [
    {
      ...
      "Status": "copying",
      ...
    }
  ]
}

Status alanına erişmek için şöyle yaparız

jq -r .DBClusterSnapshots[0].Status

Bir diğer seçenek olarak Şöyle yaparız

jshon -e DBClusterSnapshots -e 0 -e Status -u

İsimsiz Array

.[N] veya .[N] şeklinde kullanılır. Array'in içindeki bir alana erişmek için .[].keyname şeklinde kullanılır

Örnek

Şöyle yaparız

$ echo '[1, 2, 3]' | jq '.[1]'
2

Örnek

Şöyle yaparız

$ echo '[{"name": "Tony", "age": 100}, {"name": "Jane", "age": 25}]' | jq '.[].name'
"Tony"
"Jane"

Örnek

Elimizde şöyle bir kod olsun. url kısmı önemli değil.

~ curl -X GET -H "Accept: application/vnd.kafka.avro.v2+json" \
      http://localhost:... | jq

[
  {
    "topic": "movies",
    "key": null,
    "value": {
      "id": 294,
      "title": "Die Hard",
      "release_year": 1988
    },
    "partition": 0,
    "offset": 0
  },
  ...
]

Bu çıktıdan sadece "title" ve "release year" alanlarını isteyelim. Şöyle yaparız. İsmisiz array nesnesinin içindeki tüm title vs gibi alanlara erişilir

~ curl -X GET -H "Accept: application/vnd.kafka.avro.v2+json" \
      http://localhost:... | jq \
      | jq '.[] | {title: .value.title, year: .value.release_year}'

{
  "title": "Die Hard",
  "year": 1988
}
{
  "title": "Tree of Life",
  "year": 2011
}
{
  "title": "A Walk in the Clouds",
  "year": 1995
}
{
  "title": "The Big Lebowski",
  "year": 1998
}
{
  "title": "Super Mario Bros.",
  "year": 1993
}
{
  "title": "Chariots of Fire",
  "year": 1981
}

keys function

Örnek

Şöyle yaparız

$ echo '{"name": "Tony", "age": 100}' | jq 'keys'
[
  "age",
  "name"
]

length function

Örnek

Şöyle yaparız

$ echo '[1, 2, 3]' | jq 'length'
3

to_entries function

Örnek

Şöyle yaparız

$ echo '{"name": "Tony", "age": 100}' | jq 'to_entries | .[] | .value'
"Tony"
100

Conditionals and Comparisons

select(.keyname) şeklindedir

Örnek

Şöyle yaparız

$ cat file.json | jq '.[] | select(.name == "Tony")'

$ cat file.json | jq '.[] | select(.age > 100)'

$ cat file.json | jq '.[] | select(.age >= 100)'

$ cat file.json | jq '.[] | select(.age > 100 and .gender == "male")'

$ cat file.json | jq '.[] | select(.age > 100 or .gender == "female")'

--args seçeneği

array oluşturur

Örnek

Şöyle yaparız

{
    jq -n --arg key APP-Service1-Admin '{($key): $ARGS.positional}' --args a b
    jq -n --arg key APP-Service1-View  '{($key): $ARGS.positional}' --args c d
}

// Output
{
  "APP-Service1-Admin": [
    "a",
    "b"
  ]
}
{
  "APP-Service1-View": [
    "c",
    "d"
  ]
}

--join-output seçeneği

Örnek

Şöyle yaparız

$ ip -details -json link show | jq --join-output '...'

-r seçeneği 

Şöyle yaparız

jq -r '.Policy'