Ansible registers用法

Ansible registers用來捕捉一個task的輸出作爲一個變量。在Ansible的其它地方我們可以使用該變量，例如logging等。

這種變量包含了這個任務的返回值。當我們使用不同的模塊時, 會遇到的常見的返回值有：backup_file, changed, failed, invovation, msg, rc, results, skipped, stderr, stderr_lines, stdout. stdout_lines等。其它的模塊如shell, command等回有特殊的返回值。

每一個註冊過的變量在ansible任務執行的host上在執行接來下的任務時都是可用的。

讓我們來實驗一下

假設要輸出一個指定目錄下的.txt文件，我們可以用shell模塊去執行‘ls *.txt’命令並捕捉到輸出爲變量

[wlin@localhost ansible_practise]$ cat playbook.yml 
- hosts: localhost
  tasks:
  - name: Ansible register variable basic examples
    shell: "find *.txt"
    args:
      chdir: /tmp/find_output
    register: find_output

  - debug:
      var: find_output

執行結果爲：

[wlin@localhost ansible_practise]$ ansible-playbook playbook.yml 
 [WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'


PLAY [localhost] **************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************************************************************************************************
ok: [localhost]

TASK [Ansible register variable basic examples] *******************************************************************************************************************************************************************
changed: [localhost]

TASK [debug] ******************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "find_output": {
        "changed": true, 
        "cmd": "find *.txt", 
        "delta": "0:00:00.004511", 
        "end": "2020-05-21 15:59:42.901757", 
        "failed": false, 
        "rc": 0, 
        "start": "2020-05-21 15:59:42.897246", 
        "stderr": "", 
        "stderr_lines": [], 
        "stdout": "1.txt\n4.txt", 
        "stdout_lines": [
            "1.txt", 
            "4.txt"
        ]
    }
}

你可以選擇單個的參數進行輸出，例如，如果你只想知道文件的名字，你可以用find_output.stdout。

[wlin@localhost ansible_practise]$ cat playbook.yml 
- hosts: localhost
  tasks:
  - name: Ansible register variable basic examples
    shell: "find *.txt"
    args:
      chdir: /tmp/find_output
    register: find_output

  - debug:
      var: find_output
  - debug:
      var: find_output.stdout

     
[wlin@localhost ansible_practise]$ ansible-playbook playbook.yml 
 [WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'


PLAY [localhost] **************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************************************************************************************************
ok: [localhost]

TASK [Ansible register variable basic examples] *******************************************************************************************************************************************************************
changed: [localhost]

TASK [debug] ******************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "find_output": {
        "changed": true, 
        "cmd": "find *.txt", 
        "delta": "0:00:01.005628", 
        "end": "2020-05-25 14:07:52.035618", 
        "failed": false, 
        "rc": 0, 
        "start": "2020-05-25 14:07:51.029990", 
        "stderr": "", 
        "stderr_lines": [], 
        "stdout": "1.txt\n4.txt", 
        "stdout_lines": [
            "1.txt", 
            "4.txt"
        ]
    }
}

TASK [debug] ******************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "find_output.stdout": "1.txt\n4.txt"
}

PLAY RECAP ********************************************************************************************************************************************************************************************************
localhost                  : ok=4    changed=1    unreachable=0    failed=0