第 8.1 章 Playbook流程控制--条件
第 8.1 章 Playbook流程控制
1.条件 更多详情请查看：https://docs.ansible.com/ansible/latest/user_guide/playbooks_conditionals.html
2.循环
1.条件
条件判断使用关键词when ，同时使用and、or来作条件组合，when语句默认放在任务语句之后，用来判断当前条件为真时，才会执行上面的语句。
如下示例：
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这里仅基于 ansible_facts 的条件使用
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单个条件满足执行关机
tasks:
- name: Shut down Debian flavored systems
ansible.builtin.command: /sbin/shutdown -h now
when: ansible_facts['os_family'] == "Debian"
多个条件（满足其中一个）：满足CentOS 6 或者 Debain 7执行关机
tasks:
- name: Shut down CentOS 6 and Debian 7 systems
ansible.builtin.command: /sbin/shutdown -h now
when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "6") or
(ansible_facts['distribution'] == "Debian" and ansible_facts['distribution_major_version'] == "7")
多个条件（需要全部满足）：可写成列表形式
tasks:
- name: Shut down CentOS 6 systems
ansible.builtin.command: /sbin/shutdown -t now
when:
- ansible_facts['distribution'] == "CentOS"
- ansible_facts['distribution_major_version'] == "6"
如果事实或变量是字符串，并且您需要对其进行数学比较，请使用过滤器确保 Ansible 将值读取为整数：
tasks:
- ansible.builtin.shell: echo "only on Red Hat 6, derivatives, and later"
when: ansible_facts['os_family'] == "RedHat" and ansible_facts['lsb']['major_release'] | int >= 6
在setup显示信息如下：
"ansible_lsb": {
"codename": "Core",
"description": "CentOS Linux release 7.6.1810 (Core)",
"id": "CentOS",
"major_release": "7",
"release": "7.6.1810"
},
……
"ansible_os_family": "RedHat",
练习示例：
示例一：根据不同系统版本执行相关Apache安装命令：
# cat when.yml - hosts: web tasks: - name: Update apache version - yum yum: name=httpd state=present when: ansible_pkg_mgr == 'yum' notify: restart httpd - name: Update apache version - apt apt: name=apache2 state=present update_cache=yes when: ansible_pkg_mgr == 'apt' notify: restart apache2 handlers: - name: restart httpd service: name=httpd state=restarted - name: restart apache2 service: name=apache2 state=restarted
示例二：判断IP为指定值执行相应IP输出操作：
# cat when1.yml
---
- hosts: web
gather_facts: yes
remote_user: root
tasks:
- name: host 192.168.3.72 run this task
debug: msg="{{ ansible_default_ipv4.address }} 执行任务中"
when: ansible_default_ipv4.address == '192.168.3.72'
执行效果如下：
TASK [host 192.168.3.72 run this task] ********************************************************************************
skipping: [192.168.3.71]
ok: [192.168.3.72] => {
"msg": "192.168.3.72 执行任务中"
}
skipping: [192.168.3.73]
skipping: [192.168.3.74]