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
- 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={{ py3_dir }}
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)
5.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 {{ansible_distribution_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
转载自：http://www.zsythink.net/archives/2817