ansible条件判断
在工作中，我们在执行playbook时，需要对某些条件进行判断，只有当满足条件才执行相应的tasks;
1.when条件判断：只条满足when的条件时才执行对应的tasks
注：when关键字后面跟着的是python的表达式,在表达式中你能够使用任何的变量或者facts
#注：当需要用远程主机的一些信息时，gather_facts必须要开启，默认是开启状态
[root@nfs-server playbook]# cat when.yml
---
- hosts: webservers
remote_user: root
#gather_facts: False
tasks:
- name: Host 192.168.1.101 run this task
debug: ‘msg=" {{ ansible_default_ipv4.address }}"‘
when: ansible_default_ipv4.address == "192.168.2.101"
- name: memtotal < 500M and processor_cores == 2 run this task
debug: ‘msg="{{ ansible_fqdn }}"‘
when: ansible_memtotal_mb < 500 and ansible_processor_cores == 2
- name: all host run this task
shell: hostname
register: info
- name: Hostname is lamp1 Machie run this task
debug: ‘msg="{{ ansible_fqdn }}"‘
when: info[‘stdout‘] == "lamp1"
- name: Hostname is startswith l run this task
debug: ‘msg="{{ ansible_fqdn }}"‘
when: info[‘stdout‘].startswith(‘l‘)
[root@nfs-server playbook]# ansible-playbook when.yml
PLAY [webservers] **************************************************************************************************************************************
TASK [Gathering Facts] *********************************************************************************************************************************
ok: [192.168.2.101]
ok: [192.168.2.111]
TASK [Host 192.168.1.101 run this task] ****************************************************************************************************************
ok: [192.168.2.101] => {
"msg": " 192.168.2.101"
}
skipping: [192.168.2.111]
TASK [memtotal < 500M and processor_cores == 2 run this task] ******************************************************************************************
skipping: [192.168.2.101]
skipping: [192.168.2.111]
TASK [all host run this task] **************************************************************************************************************************
changed: [192.168.2.101]
changed: [192.168.2.111]
TASK [Hostname is lamp1 Machie run this task] **********************************************************************************************************
ok: [192.168.2.101] => {
"msg": "lamp1"
}
skipping: [192.168.2.111]
TASK [Hostname is startswith l run this task] **********************************************************************************************************
ok: [192.168.2.101] => {
"msg": "lamp1"
}
ok: [192.168.2.111] => {
"msg": "lamp2"
}
PLAY RECAP *********************************************************************************************************************************************
192.168.2.101 : ok=5 changed=1 unreachable=0 failed=0
192.168.2.111 : ok=3 changed=1 unreachable=0 failed=02.changed_when：先执行task,并对task返回的值进行判断，当满足changed_when指定的条件时说明是执行成功的
#注：默认情况下执行了命令的主机状态都为changed，本例对输出进行判断，包含是某个指定字符才能为changed; [root@nfs-server playbook]# cat when_1.yml --- - hosts: webservers remote_user: root #gather_facts: False tasks: - name: all host run this task shell: hostname register: info changed_when: ‘"lamp1" in info.stdout‘ [root@nfs-server playbook]# ansible-playbook when_1.yml PLAY [webservers] ************************************************************************************************************************************** TASK [Gathering Facts] ********************************************************************************************************************************* ok: [192.168.2.101] ok: [192.168.2.111] TASK [all host run this task] ************************************************************************************************************************** ok: [192.168.2.111] changed: [192.168.2.101] PLAY RECAP ********************************************************************************************************************************************* 192.168.2.101 : ok=2 changed=1 unreachable=0 failed=0 192.168.2.111 : ok=2 changed=0 unreachable=0 failed=0
3.failed_when:当执行失败后，会将信息存在register的stderr中，通过判断指定的字符是否在stderr中来确定是否真的失败；
暂时没有合适的例子，等有了再补~
本文出自 “激情燃烧的岁月” 博客，请务必保留此出处http://liuzhengwei521.blog.51cto.com/4855442/1962382
原文：http://liuzhengwei521.blog.51cto.com/4855442/1962382