Ansible - set_fact语法问题

Question

在下面的攻略中，有人能告诉我最后一条set_fact语句的语法有什么问题吗？如果我显式地指定了主机名R9 (按照第一个set_fact)，那么它就可以正常工作。但是，如果我指定一个变量的值为R9，然后在最后的set_fact语句中使用它，我会得到如下所示的错误。啊。

---
- hosts: all
  gather_facts: no

  vars:
    ansible_network_os: ios
    ansible_connection: network_cli

  tasks:
   - ios_command:  
         commands: show ip arp
     register: results

   - set_fact:
        some_var: "{{ hostvars['R9'].results }}"

   - set_fact:
       hostname: "R9"

   - set_fact:
        another_var: "{{ hostvars['{{hostname}}'].results }}"

   - debug:
       var=some_var

   - debug:
       var=another_var

错误：

fatal: [R7]: FAILED! => 
  msg: |-
    The task includes an option with an undefined variable. The error was: "hostvars['{{hostname}}']" is undefined
  
    The error appears to be in '/root/ansible/Rapid/testsetfact.yml': line 20, column 6, but may
    be elsewhere in the file depending on the exact syntax problem.
  
    The offending line appears to be:
  
  
       - set_fact:
         ^ here
fatal: [R9]: FAILED! => 
  msg: |-
    The task includes an option with an undefined variable. The error was: "hostvars['{{hostname}}']" is undefined
  
    The error appears to be in '/root/ansible/Rapid/testsetfact.yml': line 20, column 6, but may
    be elsewhere in the file depending on the exact syntax problem.
  
    The offending line appears to be:
  
  
       - set_fact:
         ^ here

Answer 1

您可以使用inventory_hostname来实现您的目的：

  - set_fact:
      another_var: "{{ hostvars[inventory_hostname].results }}"