本帖最后由 yun 于 2019-9-11 17:23 编辑
ansible是一个系列文章,我们会尽量以通俗易懂的方式总结ansible的相关知识点。 "ansible系列"中的每篇文章都建立在前文的基础之上,所以,请按照顺序阅读这些文章,否则有可能在阅读中遇到障碍。
话接前文,我们继续来聊聊关于循环的关键字。
今天聊聊 "with_indexed_items"的用法,顾名思义,"with_indexed_items"应该与"索引"有关,没错,"with_indexed_items"的作用就是在循环处理列表时为列表中的每一项添加"数字索引","索引"从0开始,这样说可能不够直观,我们来看一个小示例,示例playbook如下: - ---
- - hosts: test70
- remote_user: root
- gather_facts: no
- tasks:
- - debug:
- msg: "{{ item }}"
- with_indexed_items:
- - test1
- - test2
- - test3
复制代码上例中我们定义了一个列表,列表中有3个值,test1、test2、test3,我们使用"with_indexed_items"关键字处理这个列表,然后使用debug模块输出了item的信息,那么上例playbook执行后输出的信息如下: - TASK [debug] **********************************
- ok: [test70] => (item=(0, u'test1')) => {
- "changed": false,
- "item": [
- 0,
- "test1"
- ],
- "msg": [
- 0,
- "test1"
- ]
- }
- ok: [test70] => (item=(1, u'test2')) => {
- "changed": false,
- "item": [
- 1,
- "test2"
- ],
- "msg": [
- 1,
- "test2"
- ]
- }
- ok: [test70] => (item=(2, u'test3')) => {
- "changed": false,
- "item": [
- 2,
- "test3"
- ],
- "msg": [
- 2,
- "test3"
- ]
- }
复制代码从上述输出信息的msg中可以看到,"with_indexed_items"在处理列表中的每一项时,按照顺序为每一项添加了编号,test1对应的索引编号是0,test2的编号是1,test3的编号是2,"with_indexed_items"将添加过编号的每一项放入到了item中,所以,我们可以在处理每一项的时候同时获取到对应的编号,playbook如下 - ---
- - hosts: test70
- remote_user: root
- gather_facts: no
- tasks:
- - debug:
- msg: "index is : {{ item.0 }} , value is {{ item.1 }}"
- with_indexed_items:
- - test1
- - test2
- - test3
复制代码上例中,我们已经能够通过"with_indexed_items"获取到列表中每个项的值以及对应的编号,但是,上述两个示例都是简单的单层列表,如果遇到像前文中出现的多层嵌套列表,"with_indexed_items"会怎样处理呢?我们来试试,示例playbook如下: - ---
- - hosts: test70
- remote_user: root
- gather_facts: no
- tasks:
- - debug:
- msg: "index is : {{ item.0 }} , value is {{ item.1 }}"
- with_indexed_items:
- - [ test1, test2 ]
- - [ test3, test4, test5 ]
- - [ test6, test7 ]
复制代码如上例所示,我们定义了一个嵌套的列表,列表中的每一项又是一个小列表,我们使用"with_indexed_items"处理这个列表,上例执行后,输出如下 - TASK [debug] *****************************
- ok: [test70] => (item=(0, u'test1')) => {
- "changed": false,
- "item": [
- 0,
- "test1"
- ],
- "msg": "index is : 0 , value is test1"
- }
- ok: [test70] => (item=(1, u'test2')) => {
- "changed": false,
- "item": [
- 1,
- "test2"
- ],
- "msg": "index is : 1 , value is test2"
- }
- ok: [test70] => (item=(2, u'test3')) => {
- "changed": false,
- "item": [
- 2,
- "test3"
- ],
- "msg": "index is : 2 , value is test3"
- }
- ok: [test70] => (item=(3, u'test4')) => {
- "changed": false,
- "item": [
- 3,
- "test4"
- ],
- "msg": "index is : 3 , value is test4"
- }
- ok: [test70] => (item=(4, u'test5')) => {
- "changed": false,
- "item": [
- 4,
- "test5"
- ],
- "msg": "index is : 4 , value is test5"
- }
- ok: [test70] => (item=(5, u'test6')) => {
- "changed": false,
- "item": [
- 5,
- "test6"
- ],
- "msg": "index is : 5 , value is test6"
- }
- ok: [test70] => (item=(6, u'test7')) => {
- "changed": false,
- "item": [
- 6,
- "test7"
- ],
- "msg": "index is : 6 , value is test7"
- }
复制代码你目光如炬,一定发现了,当我们定义了两层的嵌套列表时,"with_indexed_items"会将嵌套的两层列表"拉平","拉平"后按照顺序为每一项编号,"拉平"效果跟之前总结的"with_flattened"效果类似(如果忘了怎样使用"with_flattened"请回顾前文),但是,当处理这种嵌套的多层列表时,"with_indexed_items"的拉平效果与"with_flattened"的完全一致么,我们再来实验一下,我们把上例的嵌套列表改的更加复杂一些,再多嵌套一层,示例playbook如下 - ---
- - hosts: test70
- remote_user: root
- gather_facts: no
- tasks:
- - debug:
- msg: "{{ item }}"
- with_indexed_items:
- - [ test1, test2 ]
- - [ test3, [ test4, test5 ] ]
- - [ test6 ]
复制代码如上例所示,我们又在之前示例的基础上,多嵌套了一层列表,那么执行上例playbook,输出信息如下 - TASK [debug] ********************************
- ok: [test70] => (item=(0, u'test1')) => {
- "changed": false,
- "item": [
- 0,
- "test1"
- ],
- "msg": [
- 0,
- "test1"
- ]
- }
- ok: [test70] => (item=(1, u'test2')) => {
- "changed": false,
- "item": [
- 1,
- "test2"
- ],
- "msg": [
- 1,
- "test2"
- ]
- }
- ok: [test70] => (item=(2, u'test3')) => {
- "changed": false,
- "item": [
- 2,
- "test3"
- ],
- "msg": [
- 2,
- "test3"
- ]
- }
- ok: [test70] => (item=(3, [u'test4', u'test5'])) => {
- "changed": false,
- "item": [
- 3,
- [
- "test4",
- "test5"
- ]
- ],
- "msg": [
- 3,
- [
- "test4",
- "test5"
- ]
- ]
- }
- ok: [test70] => (item=(4, u'test6')) => {
- "changed": false,
- "item": [
- 4,
- "test6"
- ],
- "msg": [
- 4,
- "test6"
- ]
- }
复制代码你肯定看出了问题所在,没错,当多加了一层嵌套以后,"with_indexed_items"并不能像"with_flattened"一样将嵌套的列表"完全拉平",第二层列表中的项如果仍然是一个列表,"with_indexed_items"则不会拉平这个列表,而是将其当做一个整体进行编号。
关于"with_indexed_items"的使用就总结到这里,希望能够对你有所帮助。
|