Using Key(#) function to extract keys from an object in Ansible - json

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": ""
}

Answer 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() }}"

Answer 2

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