brief introduction

In the daily development under linux, we often need to process and analyze the json format data. jq Is an open source JSON format data processing tool, it provides a lot of flexible syntax, very powerful.

install

• macOS:

brew install jq

• Ubuntu

apt-get install jq

• Other reference Official website

jq syntax

Basic usage

Suppose that the text test ABCD JSON has the following string

{
    "name":"xiaoming",
    "age":21,
    "birthday":"10th August",
    "email":"yj.xxxx@xxxx.com",
    "skills":[
        {
            "name":"C++",
            "level":2
        },
        {
            "name":"Python",
            "level":1
        }
    ]
}

Filter by key

jq expression

cat test_json | jq ".name"

output

"xiaoming"

Filter by index

jq expression

cat test_json | jq ".skills[0]"

output

{
  "name": "C++",
  "level": 2
}

Traversing array

jq expression

cat test_json | jq ".skills[]"

output

{
  "name": "C++",
  "level": 2
}
{
  "name": "Python",
  "level": 1
}

Filter by Pipe ("|)

jq expression

cat test_json | jq ".skills[] | .level"

output

2
1

Construct Array

jq expression

cat test_json | jq "[.age, .email]"

output

[
  21,
  "yj.xxxx@xxxx.com"
]

Construct Mapping

jq expression

cat test_json | jq "{name, skills_2 : .skills}"

output

{
  "name": "xiaoming",
  "skills_2": [
    {
      "name": "C++",
      "level": 2
    },
    {
      "name": "Python",
      "level": 1
    }
  ]
}

jq expression

cat test_json | jq "{(.name): .skills}"

output

{
  "xiaoming": [
    {
      "name": "C++",
      "level": 2
    },
    {
      "name": "Python",
      "level": 1
    }
  ]
}

Built in operators and functions

addition

jq expression

cat test_json | jq ".age + 1"

output

22

Character mosaic

cat test_json | jq ".age + .name"

output

"yj.xxxx@xxxx.comxiaoming"

Subtraction -

jq expression

echo '["xml", "yaml", "json"]' | jq '. - ["xml", "yaml"]'

output

[
  "json"
]

Length

jq expression

echo '[[1,2], "string", {"a":2}, null]' | jq '[.[]| length]'

output

[
  2,
  6,
  1,
  0
]

keys

jq expression

cat test_json | jq 'keys'

output

[
  "age",
  "birthday",
  "email",
  "name",
  "skills"
]

in

jq expression

echo '["foo", "bar"]' | jq '.[] | in({"foo": 42})'

output

true
false

map

jq expression

echo '[1,2,3]' | jq 'map(.+1)'

output

[
  2,
  3,
  4
]

map_values

jq expression

echo '{"a": 1, "b": 2, "c": 3}' | jq 'map_values(.+1)'

output

{
  "a": 2,
  "b": 3,
  "c": 4
}

del

js expression

echo '{"foo": 42, "bar": 9001, "baz": 42}' | jq "del(.foo)"

output

{
  "bar": 9001,
  "baz": 42
}

select

jq expression

echo '[{"id": "first", "val": 1}, {"id": "second", "val": 2}]' | jq '.[] | select(.id == "second")'

output

{
  "id": "second",
  "val": 2
}

any

jq expression

echo '[true, false]' | jq 'any'

output

true

all

jq expression

echo '[true, false]' | jq 'all'

output

false

min,max

jq expression

echo '[5,4,2,7]' | jq 'min'

output

2

sort,sort_by

jq expression

echo '[8,3,null,6]' | jq 'sort'

output

[
  null,
  3,
  6,
  8
]

jq expression

echo '[{"foo":4, "bar":10}, {"foo":3, "bar":100}, {"foo":2, "bar":1}]' | jq 'sort_by(.foo)'

output

[
  {
    "foo": 2,
    "bar": 1
  },
  {
    "foo": 3,
    "bar": 100
  },
  {
    "foo": 4,
    "bar": 10
  }
]

index

jq expression

echo '["a","b", "c"]' | jq 'index("b")'

output

1

json

jq expression

echo '["a","b","c"]' | jq 'join(";")'

output

"a;b;c"

Conditional judgement

jq expression

echo 2 | jq 'if . == 0 then  "zero" elif . == 1 then "one" else  "many" end'

output

"many"

Reference resources

• Official references