Using Key(@) function to extract keys from an object in Ansible

Question

I have a file file.sub which contains this JSON object {"kas_sub.test1": "true", "kas_sub.test2": "true"}. I would extract the keys and to get this: kas_sub.test1 kas_sub.test1. When i try

- shell: 'cat path/to/file.sub'
  register: file1
- debug:
    var: file1.stdout_lines

I got:

TASK [shell] *****************************************************************************************************************
changed: [ansible4]
changed: [control]

TASK [debug] *****************************************************************************************************************
ok: [control] => {
    "file1.stdout_lines": [
        "{\"kas_sub.tes1\": \"true\", \"kas_sub.test2\": \"true\"}"
    ]
}

So it's not conserving the same JSON format because i would use the json_query filter.

     
- debug:
    msg: "{{ file1.stdout_lines| json_query(value1)}}"
  vars:
    value1: "@[?keys(@)]"

keys(@)function doesn't return anything

ok: [control] => {
    "msg": ""
}

score 1 · Accepted Answer · answered Aug 03 '22 at 10:42

1

^{note: taking for granted you want to read a file on the target machine}

In a nutshell:

- hosts: your_group
  gather_facts: false

  vars:
    file_to_read: /path/to/file.sub

  tasks:
    - name: slurp file content from target
      slurp:
        src: "{{ file_to_read }}"
      register: slurped_file

    - name: display keys from json inside file
      debug:
        msg: "{{ (slurped_file.content | b64decode | from_json).keys() }}"

answered Aug 03 '22 at 10:42

Zeitounator

38,476
7
53
66

man you rock, it's working as expected, the `slurp` module resolved it. thank you for your help again. Please could you explain why with the `cat` command the format changes `"{\"kas_sub.tes1\": \"true\", \"kas_sub.test2\": \"true\"}"`? – medisamm Aug 03 '22 at 11:03
1

If you use `from_json` on your entire `cat` output (i.e. `file1.stdout`) it will just work the same. But it is a bad practice to use shell when you have a module doing the job. – Zeitounator Aug 03 '22 at 11:17
i got it so just applying `from_json` will give the same orginal format `{"kas_sub.test1": "true", "kas_sub.test2": "true"}`. Exactly using a module doing the job is better then shell module Thank you again – medisamm Aug 03 '22 at 11:31

score 1 · Answer 2 · answered Aug 03 '22 at 11:15

1

_{Given the file
shell> cat /tmp/file.sub
{"kas_sub.test1": "true", "kas_sub.test2": "true"}}

Use jq (if you can). For example, get the keys

    - command: jq 'keys' /tmp/file.sub
      register: result

and convert them to a list

keys: "{{ result.stdout|from_yaml }}"

gives

keys:
  - kas_sub.test1
  - kas_sub.test2

^{Example of a complete playbook
- hosts: localhost
vars:
keys: "{{ result.stdout|from_yaml }}"
tasks:
- command: jq 'keys' /tmp/file.sub
register: result
- debug:
var: keys}

answered Aug 03 '22 at 11:15

Vladimir Botka

58,131
4
32
63

thank you so much @Vladimir Botka,`jq` is not installed i will install it and give it a try. I really appreciate it – medisamm Aug 03 '22 at 11:34
1

It depends on the use case. Make your choice. You're welcome. – Vladimir Botka Aug 03 '22 at 11:43

Using Key(@) function to extract keys from an object in Ansible

2 Answers2