[TOC]
`when` 语句用来判断哪些目标主机来执行当前 tasks
`with_items` 语句来循环某一个变量列表，然后将每次循环的结果放进 `item` 中
示例：
### 使用 when 判断是否执行
```
---
- hosts: k8s
become: yes
vars:
old_gw: "192.168.222.1"
new_gw: "192.168.222.3"
tasks:
- name: find netplan yaml file
shell: find /tmp/ -name "00-installer-config.yaml"
register: interface_name
when:
- ansible_distribution == "Ubuntu"
- ansible_distribution_version == "20.04"
- name: replace gateway
replace:
path: "{{ item }}"
regexp: "{{ old_gw }}"
replace: "{{ new_gw }}"
with_items:
- "{{ interface_name.stdout_lines }}"
#循环interface_name输出的stdout_lines内容，然后放到 {{ item }}中
when:
- ansible_distribution == "Ubuntu"
- ansible_distribution_version == "20.04"
- name: check
shell: cat {{ item }}
register: file_info
with_items: "{{ interface_name.stdout_lines }}"
when:
- ansible_distribution == "Ubuntu"
- ansible_distribution_version == "20.04"
- name: debug
debug:
msg: "{{ file_info.results[0].stdout_lines }}"
```
### 使用 when 判断 item 的个数
```
tasks:
- name: Run with items greater than 5
ansible.builtin.command: echo {{ item }}
loop: [ 0, 2, 4, 6, 8, 10 ]
when: item > 5
```
