Modifying yaml array in bash

Question

I have a file with below content,

- groups:
  - system:bootstrappers
  - system:nodes
  rolearn: arn:aws:iam::1234566:role/radeks-project-us-east-1-NodeInstanceRole
  username: system:node:{{EC2PrivateDNSName}}

I want to append this file content as shown below with eks ,iammappings as first two lines,

eks:
  iammappings:
  - groups:
  - system:bootstrappers
  - system:nodes
  rolearn: arn:aws:iam::1234566:role/radeks-project-us-east-1-NodeInstanceRole
  username: system:node:{{EC2PrivateDNSName}}

I tried yq merge.But It didnt work for me.Please let me know how to do this.

But I need to add eks: ,iammappings as parents yaml tags to the array — Rad4
– Rad4, Commented Jul 14, 2020 at 22:38
FYI, all JSON files are also valid YAML files. Even if your input is formatted in a way that's conventional YAML, it'll work perfectly fine if your output is just JSON -- which means you have a much wider array of tools that can write it. — Charles Duffy
– Charles Duffy, Commented Jul 14, 2020 at 23:10
...and are you sure your stated output is right? The way you state it, groups is the key in a dictionary whose value is null, and system:bootstrappers and system:nodes are not inside groups, but instead are separate items in the iammappings list. — Charles Duffy
– Charles Duffy, Commented Jul 14, 2020 at 23:17

bigbounty · Accepted Answer · 2020-07-14 23:12:27Z

1

There is a specific tool for parsing yaml in bash i.e yq same as jq. Link - https://github.com/mikefarah/yq

You have to modify the source yaml file as follows

- groups:
    - system:bootstrappers
    - system:nodes
    - rolearn: arn:aws:iam::1234566:role/radeks-project-us-east-1-NodeInstanceRole
    - username: system:node:{{EC2PrivateDNSName}}

Else yq won't accept it as proper yaml file.

Next to get your job done use the following command

yq p -i file.yaml 'eks.iammappings'

The above command uses prefix function and will replace in place. The contents of the file will be as follows

eks:
  iammappings:
    - groups:
        - system:bootstrappers
        - system:nodes
        - rolearn: arn:aws:iam::1234566:role/radeks-project-us-east-1-NodeInstanceRole
        - username: system:node:{{EC2PrivateDNSName}}

edited Jul 14, 2020 at 23:12

answered Jul 14, 2020 at 23:03

bigbounty

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2 Comments

Charles Duffy Over a year ago

Incidentally, the OP already knows about yq -- they asked a question about its use just this morning.

bigbounty Over a year ago

@CharlesDuffy He didn't try yq prefix

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