How to append a line using sed in Linux yaml file after matching exact string

Question

I am not able to find a way to append a line in yaml file after exact match of string but ignoring similar string having other values in it in a line. There are some example but that is not my case. I have a yaml file and I am automating its configuration instead of adding values manually by going to line number, I am trying to find out a string and then after that, I am adding the value using sed command.

Here is the example

My current file a.yaml

rules:
  - name: Block PH by GeoIP country
    script: ./rules/Block PH by GeoIP country.js
    stage: login_success
    enabled: false
........
........
........
- name: Preview-1 API (Test Application)
  allowed_clients: []
  app_type: non_interactive
  callbacks: []                             <<<<< -------  see string "callbacks:" with brackets
  client_aliases: []
........
........
........
  allowed_logout_urls:
    - 'http://local.example.com:/login'
  allowed_origins: []
  callbacks:                           <<<<< -------  see string "callbacks:" where I want to append
    - 'http://local.example.com:/callback'

Command

sed -i "/callbacks:/a \ \ \ \ \ \ - 'https://d1.example.com/callback'" > a.yaml

Results of the Command

My Updated File a.yaml

rules:
  - name: Block PH by GeoIP country
    script: ./rules/Block PH by GeoIP country.js
    stage: login_success
    enabled: false
........
........
........
- name: Preview-1 API (Test Application)
  allowed_clients: []
  app_type: non_interactive
  callbacks: []                             
    - 'https://d1.example.com/callback'   <<<<< -------  see problem here
  client_aliases: []
........
........
........
  allowed_logout_urls:
    - 'http://local.example.com:/login'
  allowed_origins: []
  callbacks:                           
    - 'https://d1.example.com/callback'          <<<<< -------  I appended
    - 'http://local.example.com:/callback'

What I want

    rules:
  - name: Block PH by GeoIP country
    script: ./rules/Block PH by GeoIP country.js
    stage: login_success
    enabled: false
........
........
........
- name: Preview-1 API (Test Application)
  allowed_clients: []
  app_type: non_interactive
  callbacks: []                                <<<<< -------  I don't want to append here
  client_aliases: []
........
........
........
  allowed_logout_urls:
    - 'http://local.example.com:/login'
  allowed_origins: []
  callbacks:                           
    - 'https://d1.example.com/callback'          <<<<< -------  I want my addition only after this
    - 'http://local.example.com:/callback'

I don't want to append my line after every matching string, in my above example there are 2 lines having 2 values callbacks: [] and callbacks: so I am trying to append after callbacks: only.

Scenario

I wanted to use sed command in my bash script file where I will pass variable value for this line like this - 'https://$1.example.com/callback' and command would be like this

sed -i "/callbacks:/a \ \ \ \ \ \ - 'https://$1.example.com/callback'" > a.yaml

In this way I can reuse this script by passing any value and append line which will look as below

  callbacks:               
    - 'https://z.example.com/callback'
    - 'https://b.example.com/callback'
    - 'https://d1.example.com/callback'
    - 'http://local.example.com:/callback'

Answer 1

You could use $ to match the end of the line:

sed -i "/callbacks:$/a\
\    - 'https://d1.example.com/callback'" a.yaml