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ansible 笔记 条件判断

2020/01/14 ansible

  1. 判断目录或文件是否存在

    ```

    • hosts: cf601 remote_user: root gather_facts: no vars: testpath: /testdir tasks:
      • debug: msg: “file exist” when: testpath is exists #不存在就用testpath is not exists

  2. 判断变量

    • defined: 判断变量是否已经定义，已经定义则为真
    • undefined: 判断变量是否已经定义，未定义则返回真
    • none: 判断变量是否已经定义，如果变量值已经定义，但是变量值为空，则返回真

    例:

     - hosts: cf601
   remote_user: root
   gather_facts: no
   vars:
     testvar: "test"
     testvar1:
   tasks:
   - debug:
       msg: "Variable is defined"
     when: testvar is defined
   - debug:
       msg: "Variable is undefined"
     when: testvar2 is undefined
   - debug:
       msg: "The variable is defined, but there is no value"
     when: testvar1 is none

  3. 判断执行结果

    • success或succeeded: 通过任务的返回信息判断任务的执行状态，任务执行成功则返回真
    • failure或failed: 通过任务的返回信息判断任务的执行状态，任务执行失败则返回真
    • change或changed: 通过任务的返回信息判断任务的执行状态，任务执行状态为changed则返回真
    • skip或skipped: 通过任务的返回信息判断任务的执行状态，当任务没有满足条件，而被跳过执行时，则返回真
     - hosts: cf601
   remote_user: root
   gather_facts: no
   vars:
     doshell: "yes"
   tasks:
   - shell: "cat /testdir/abc"
     when: doshell == "yes"
     register: returnmsg
     ignore_errors: true
   - debug:
       msg: "success"
     when: returnmsg is success
   - debug:
       msg: "failed"
     when: returnmsg is failure
   - debug:
       msg: "changed"
     when: returnmsg is change
   - debug:
       msg: "skip"
     when: returnmsg is skip

    稍加改变看看三种情况的结果

  4. 判断路径

    • file: 判断路径是否是一个文件，如果路径是一个文件则为真（该参数在实际使用我碰到过问题，暂时不考虑使用可以使用stat来代替例如：
     - name: check if exists /usr/local/bin/python3
   stat: path=
   register: dir_stat
	
 - name: check py3 is installed and force exit
   fail: msg="python3 has been installed already!"
   when: dir_stat.stat.exists
    • directory: 判断路径是否是一个目录，如果路径是一个目录则为真
    • link: 判断路径是否是一个软连接，如果路径是一个软连接则为真
    • mount: 判断路径是否是一个挂载点，如果路径是一个挂载点则为真
    • exists: 判断路径是否存在，如果路径存在则为真

    注意：某些版本之前可能需要加上“is_”前缀

     - hosts: cf601
   remote_user: root
   gather_facts: no
   vars:
     testpath1: "/testdir/test"
     testpath2: "/testdir/"
     testpath3: "/testdir/testsoftlink"
     testpath4: "/testdir/testhardlink"
     testpath5: "/boot"
   tasks:
   - debug:
       msg: "file"
     when: testpath1 is file
   - debug:
       msg: "directory"
     when: testpath2 is directory
   - debug:
       msg: "link"
     when: testpath3 is link
   - debug:
       msg: "link"
     when: testpath4 is link
   - debug:
       msg: "mount"
     when: testpath5 is mount
   - debug:
       msg: "exists"
     when: testpath1 is exists

  5. 判断整除（比较少用）

    • even: 判断数值是否是偶数，偶数则为真
    • odd: 判断数值是否是奇数，奇数则为真
    • divisibleby(num): 判断是否可以整除指定的数值，如果除以指定的值以后余数为0，则返回真
     - hosts: cf601
   remote_user: root
   gather_facts: no
   vars:
     num1: 4
     num2: 7
     num3: 64
   tasks:
   - debug:
       msg: "An even number"
     when: num1 is even
   - debug:
       msg: "An odd number"
     when: num2 is odd
   - debug:
       msg: "Can be divided exactly by"
     when: num3 is divisibleby(8)

  6. 其他

    • version: 可以用于对比两个版本号的大小，或者与指定的版本号进行对比，语法version（’版本号’，’比较操作符’）

    2.5版本此test从version_compare 更名为version

     - hosts: test70
   remote_user: root
   vars:
     ver: 7.4.1708
     ver1: 7.4.1707
   tasks:
   - debug:
       msg: "This message can be displayed when the ver is greater than ver1"
     when: ver is version(ver1,">")
   - debug:
       msg: "system version  greater than 7.3"
     when: ansible_distribution_version is version("7.3","gt")

    这里的例子里面两种比较都是可以的 支持多种风格操作符。

    • subset: 判断一个list是不是另一个list的子集，是则为真
    • siperset: 判断一个list是不是另一个list的父集，是则为真

    注：2.5版本之前是issubset和issuperset

```

  • hosts: cf601 remote_user: root gather_facts: no vars: a:
    • 2
    • 5 b: [1,2,3,4,5] tasks:
    • debug: msg: “A is a subset of B” when: a is subset(b)
    • debug: msg: “B is the parent set of A” when: b is superset(a) string: 判断对象是否是一个字符串，是则为真 number: 判断对象是否是一个数字，是则为真
  • hosts: cf601 remote_user: root gather_facts: no vars: testvar1: 1 testvar2: “1” testvar3: a tasks:
    • debug: msg: “This variable is a string” when: testvar1 is string
    • debug: msg: “This variable is a string” when: testvar2 is string
    • debug: msg: “This variable is a string” when: testvar3 is string
  • debug: msg: “This variable is number” when: testvar1 is number
    • debug: msg: “This variable is a number” when: testvar2 is number
    • debug: msg: “This variable is a number” when: testvar3 is number

转自 简书

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