EX294: Use variables to retrieve the results of running a command

official doc link: register variables

0. Basic Idea

Ansible modules return JSON data. To make use of this returned data, Ansible can save a module's return as a variable, which is done by directive "register". From then on, the following tasks can reference this variable.

---
- hosts: home
  gather_facts: no
  tasks:
      - name: get data time
        shell: date '+%Y%m%d %H:%M:%S'
        register: result

      - name: print result
        debug: var=result

Let's have a look at what's the return data of the above example.

$ ansible-playbook playbook.yml

PLAY [home] ************************************************************************************************

TASK [get date time] **********************************************************************************

changed: [192.168.0.19]

TASK [print result] ****************************************************************************************

ok: [192.168.0.19] => {

    "result": {

        "ansible_facts": {

            "discovered_interpreter_python": "/usr/bin/python"

        },

        "changed": true,

        "cmd": "date '+%Y%m%d %H:%M:%S'",

        "delta": "0:00:00.009413",

        "end": "2019-11-27 22:55:25.818248",

        "failed": false,

        "rc": 0,

        "start": "2019-11-27 22:55:25.808835",

        "stderr": "",

        "stderr_lines": [],

        "stdout": "20191127 22:55:25",

        "stdout_lines": [

            "20191127 22:55:25"

        ]

    }

}

1 Key points

• registered variables are at the host-level, just like facts.
• registered variables are saved in memory
• registered variables can only be used by tasks running on the same host
• different modules return different data, please see their doc for data format