Shell：jq 循环 json 对象, jq 循环 json 数组, jq 用法实践, jq converts a JSON object to key=value, jq parses one field from an JSON array into bash array

 

1. 转换数字为字符串 How do I use jq to convert number to string?

Given the following jq command and Json:

jq '.[]|[.string,.number]|join(": ")' <<< '
[
  {
    "number": 3,
    "string": "threee"
  },
  {
    "number": 7,
    "string": "seven"
  }
]
'

I’m trying to format the output as:

three: 3
seven: 7

 

方法：The jq command has the tostring function. It took me a while to learn to use it by trial and error. Here is how to use it:

jq -r '.[] | [ .string, .number|tostring ] | join(": ")' <<< '
[{ "number": 9, "string": "nine"},
 { "number": 4, "string": "four"}]
'
#nine: 9
#four: 4

 

2. 转换 json 对象为 key=value 形式，How to convert a JSON object to key=value format in jq?

In jq, how can I convert a JSON to a string with key=value?

From:

{
    "var": 1,
    "foo": "bar",
    "x": "test"
}

To:

var=1
foo=bar
x=test

 

方法：You could try:

jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]" test.json

Here’s a demo:

$ cat test.json
{
    "var": 1,
    "foo": "bar",
    "x": "test"
}
$ jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]" test.json

#foo=bar
#var=1
#x=test

 

或者可以使用：

$ cat data.json
{
  "SITE_DATA": {
    "URL": "example.com",
    "AUTHOR": "John Doe",
    "CREATED": "10/22/2017"
  }
}

You can make a much simpler version of the jq program:

jq -r '.SITE_DATA | to_entries | .[] | .key + "=\"" + .value + "\""'

which outputs:

URL="example.com"
AUTHOR="John Doe"
CREATED="10/22/2017"

This string is evalable as long as the characters `, $, newline and null don’t appear in the data:

eval "$(jq -r '.SITE_DATA | to_entries | .[] | .key + "=\"" + .value + "\""' < data.json)"
echo "$AUTHOR"

 

或者：

Just realized that I can loop over the results and eval each iteration:

constants=$(cat ${1} | jq '.SITE_DATA' | jq -r "to_entries|map(\"\(.key)=\(.value|tostring)\")|.[]")

for key in ${constants}; do
  eval ${key}
done

Allows me to do:

echo ${AUTHOR}
# outputs John Doe

 

3.  将输出化为一行 Get outputs from jq on a single line

-c is what you likely need

Using the output you posted above, you can process it further:

jq -c . input

To Give;

{"key":"SEA-739","status":"Open","assignee":null}
{"key":"SEA-738","status":"Resolved","assignee":"user2@mycompany.com"}

Or you can just change your original command

FROM

jq -r '(.issues[] | {key, status: .fields.status.name, assignee: .fields.assignee.emailAddress})'

TO

jq -c '(.issues[] | {key, status: .fields.status.name, assignee: .fields.assignee.emailAddress})'

 

4. json 数组转 bash 数组 parse one field from an JSON array into bash array

I have a JSON output that contains a list of objects stored in a variable. (I may not be phrasing that right)

[
  {
    "item1": "value1",
    "item2": "value2",
    "sub items": [
      {
        "subitem": "subvalue"
      }
    ]
  },
  {
    "item1": "value1_2",
    "item2": "value2_2",
    "sub items_2": [
      {
        "subitem_2": "subvalue_2"
      }
    ]
  }
]

Using jq :

$ cat json
[
  {
    "item1": "value1",
    "item2": "value2",
    "sub items": [
      {
        "subitem": "subvalue"
      }
    ]
  },
  {
    "item1": "value1_2",
    "item2": "value2_2",
    "sub items_2": [
      {
        "subitem_2": "subvalue_2"
      }
    ]
  }
]

CODE:

arr=( $(jq -r '.[].item2' json) )
printf '%s\n' "${arr[@]}"

OUTPUT:

value2
value2_2

 

5. jq 遍历 json 数组，遍历 json 对象，Bash for Loop Over JSON Array Using jq

First we will start with some data:

sample='[{"name":"foo"},{"name":"bar"}]'  
echo "${sample}" | jq '.'

输出

[
  {
    "name": "foo"
  },
  {
    "name": "bar"
  }
]

By using jq --compact-output (or -c) we can get each object on a newline.

sample='[{"name":"foo"},{"name":"bar"}]'  
echo "${sample}" | jq -c '.[]'

输出

{"name":"foo"}
{"name":"bar"}

We could start iterating of the above with a Bash for loop if our data does not contain spaces or newlines. But since certificates contain newlines we better base64 encode each line. Also, instead of -c, we now use -r to get rid of the extra quotes.

sample='[{"name":"foo"},{"name":"bar"}]'  
echo "${sample}" | jq -r '.[] | @base64'

输出

eyJuYW1lIjoiZm9vIn0=  
eyJuYW1lIjoiYmFyIn0=

Now let’s build our for loop.

sample='[{"name":"foo"},{"name":"bar"}]'  
for row in $(echo "${sample}" | jq -r '.[] | @base64'); do  
    _jq() {
     echo ${row} | base64 --decode | jq -r ${1}
    }

   echo $(_jq '.name')
done

输出

foo  
bar

 

实例：

cat test.json | jq -c -r ".[] | {status : .status}" | while read row
do
    _jq() {
        echo ${row} | jq -r ${1}
    }

    echo $(_jq '.status')

done

以上代码等同于：

cat test.json | jq -r ".[] | {status: .status} | @base64"  | while read row
do
    _jq() {
        echo ${row} | base64 --decode | jq -r ${1}
    }

   echo $(_jq '.status')
done

 

6. 解决报错：parse error: Invalid string: control characters from U+0000 through U+001F must be escaped at line 3, column 9 或者 jq: error (at :1): Cannot index string with string “expand”

Newlines not supported on jqplay with jq 1.5. They must be escaped as \n or as \u000a.

一般原因是因为 jq 1.5的版本不知道 json 换行，解决方法如下：

json_string=$(echo ${string} | tr '\r\n' ' ')

#或者采用直接删除的方式
json_string=$(echo ${string} | tr -d '\r\n')

通过 tr 函数做一个替换即可！

 

7. jq 在线测试网站：

在线测试：https://jqplay.org/

手册：https://stedolan.github.io/jq/manual/

 

本文：Shell：jq 循环 json 对象, jq 循环 json 数组, jq converts a JSON object to key=value, jq parses one field from an JSON array into bash array