Using jq parse a json output to get specific properties as a new json output

Question

I am very new to jq, I am trying to parse an output json I get from command -

aws cloudformation list-stacks --stack-status-filter CREATE_COMPLETE

to get a new output where values of the key matches to certain pattern.

for example this is my json output from previous command -

{
  "StackSummaries": [
    {
      "StackId": "arn:aws:213dqwqwdqwdqwdq",
      "StackName": "monkeyman",
      "CreationTime": "2017-06-06T20:52:59.728Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "Liaison API ELB cloud formation script"
    },
    {
      "StackId": "arn:aws:csdfsdfcsdfsdfsdfsdfsdfgdfgfdg",
      "StackName": "monkeyman2",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "yoohooo instance"
    },
    {
      "StackId": "arn:aws:sdffgds444fsdfsdfgdfgfdg",
      "StackName": "starfish2",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "helloworld instance"
    },
    {
      "StackId": "arn:aws:csdfsdfcsdfsdfsdfsdfsdfgdfgfdg",
      "StackName": "bulldog4",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "night night instance"
    },
    {
      "StackId": "arn:aws:yhyhyhyhyhysdfgdfgfdg",
      "StackName": "carrotman",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "surprise mo instance"
    }

  ]

}

Here I need to create a new output json by piping the first output to jq where StackName startsWith monkeyman and bulldog and which should look like -

{
  "StackSummaries": [
    {
      "StackId": "arn:aws:213dqwqwdqwdqwdq",
      "StackName": "monkeyman",
      "CreationTime": "2017-06-06T20:52:59.728Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "Liaison API ELB cloud formation script"
    },
    {
      "StackId": "arn:aws:csdfsdfcsdfsdfsdfsdfsdfgdfgfdg",
      "StackName": "monkeyman2",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "yoohooo instance"
    },
    {
      "StackId": "arn:aws:csdfsdfcsdfsdfsdfsdfsdfgdfgfdg",
      "StackName": "bulldog4",
      "CreationTime": "2017-06-06T20:51:55.191Z",
      "StackStatus": "CREATE_COMPLETE",
      "TemplateDescription": "night night instance"
    }

  ]

}

I have tried a lot, I was able to do it somehow using basic unix split and regex commands but something tells me it would be easier and less cumbersome to do directly with jq.

Amazon supports this natively. We don't need 'jq' to achieve this. Refer this link: opensourceconnections.com/blog/2015/07/27/… which explains how to achieve this. — krishna_mee2004
– krishna_mee2004, Commented Jun 27, 2017 at 14:22

user197693 · Accepted Answer · 2017-06-07 01:01:45Z

3

It is easy with jq

jq '.[] |= map(select(.StackName | startswith("monkeyman"), startswith("bulldog")))'

In a nutshell, map(x) applies x to every object that is fed to it. select(y) selects the objects that meet the condition y. In this case, condition y is that there is a key called StackName whose value starts with either "monkeyman" or "bulldog".

edited Jun 7, 2017 at 1:01

answered Jun 7, 2017 at 0:06

user197693

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