Ansible Playbook の基本 | when / assert の条件指定 記法まとめ

true / false 判定

when に変数を渡せば true / false の判定が出来る。

• when: some_variable
• when: not some_variable

Boolean以外が入った変数も判定条件として使える。
たとえば文字列の場合は、値が存在すれば true と、空であれば false として評価される様子。

is defined

変数が定義済みかどうかを判定できる。

• when: some_variable is defined
• when: some_variable is not defined

is succeeded / is failed / is changed / is skipped

変数が辞書 (ハッシュ) の場合は、以下の特殊文法が使える。

• when: dictionary is succeeded
• when: dictionary is failed
• when: dictionary is changed
• when: dictionary is skipped

それぞれ

• dictionary.failed
• dictionary.change
• dictionary.skipped

の値の true / false を判定する。

( is succeeded は dictionary.failed の値を見ており、 failed が false だったり、 そもそも failed キーない場合にもマッチする模様 )

in

• 文字列の中に文字列が含まれていること
• 配列の中に要素があること

などを検証できる。

• when: "'somebody' in 'Everybody here is somebody'"
• when: "'banana' in fruits"

複合条件

when に複数の条件を配列で渡すことが出来る。
この場合、AND条件でひとつずつ評価される。

when:
  - some_not_defined_variable is defined
  - some_not_defined_variable # 評価されない

この例の場合だと、一個目の判定でそれ以降の評価を諦めるので、二個目は評価されない。

and や or で条件をつなげて、ひとつの when に 複数条件を渡すことも出来る。

when: some_not_defined_variable is defined and some_not_defined_variable

Playbookの例

- hosts: localhost
  tasks:
    - set_fact:
        alice:
          name: Alice
          job: not engineer
          age: 98
          evil_mind: # empty string 
          changed: true
          skipped: true
          failed: false
          kicked: true

    # present string evaluate as true
    - debug:
        msg: "Alice's name is {{ alice.name }}"
      when:
        - alice.name

    # not present string evaluate as false
    - debug:
        msg: "Alice is not evil"
      when:
        - not alice.evil_mind

    # You can use "is succeeded" conditional syntax
    # when alice dictionary has "failed" key and false value then evaluated as succeeded
    - debug:
        msg: "Alice has succeeded as not enginner"
      when:
        - alice is succeeded

    - debug:
        msg: "Alice is not evil"
      when:
        - not alice.evil_mind

    # You can use "is changed" conditional syntax
    # because alice dictionary has "changed" key and boolean value
    - debug:
        msg: "Alice was changed"
      when:
        - alice is changed

    # You can use "is failed" conditional syntax
    # because alice dictionary has "failed" key and false value
    - debug:
        msg: "Alice was not failed to swimming"
      when:
        - alice is not failed

    # You can use "is skipped" conditional syntax
    # because alice dictionary has "skipped" key and true value
    - debug:
        msg: "Alice skipped school programs when she was a child."
      when:
        - alice is skipped

    # You can not use some new original conditional syntax
    #  The conditional check 'alice is kicked' failed. The error was: template error while templating string: no test named 'kicked'
    # - debug:
    #    msg: "Alice has kicked from chat room"
    #  when:
    #    - alice is kicked

    - name: This task will be skipped because alice has no not_found key in he dictionary
      debug:
        msg: "Can you see unknown information of Alice?"
      when:
        - alice.not_found is defined

    - set_fact:
        bob:
          failed: true

    - debug:
        msg: "{{ bob }}"

    - name: 'This task will be skipped because bob has failed key value on his dictionary'
      debug:
        msg: "Bob is succeeded even he does not say anything."
      when:
        - bob is succeeded

    - name: 'This task will be skipped because bob has not changed key on his dictionary'
      debug:
        msg: "Bob is succeeded even he does not say anything."
      when:
        - bob is change

    - set_fact:
        carol:
          name: carol

    - debug:
        msg: Carol is succeeded because she has no failed in her dictionary
      when:
        - carol is succeeded
        - carol is not failed

環境

• ansible 2.6.0

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