Ansible variables, Lists, Dictionaries

 There are many boring tasks in your daily job which can be automated easily if you know some of the tools like here, Ansible. Let's explore more on how to use the variables in the playbooks.

In this post we will be covering :

1. Basic datatypes
2. List variables and using them
3. Dictionary variable and accessing them

Variables and Datatypes in Ansible

In Ansible variables can be defined under global tasks or they can be defined at local to a task level. support all the Python supported datatypes.

---
# Filename: varibles_datatypes.yml
 - name: varibles in ansible
   hosts: localhost
   gather_facts: false
   vars:
     a: "Vybhava Technologies"
     b: yes
     n: 100
     m: 500.99
   tasks:
     - debug:
         msg:
           - "a= {{ a }} a type: {{ a |type_debug }}"
           - "b= {{ b }} b type: {{ b |type_debug }}"
           - "n= {{ n }} n type: {{ n |type_debug }}"
           - "m= {{ m }} m type: {{ m |type_debug }}"

The execution output is :

ansible-playbook varibles_datatypes.yml

 

Screenshot

Ansible Lists

In Ansible List object is similar to the Python list. Which can be assigned alist variable within a single line or lease it can be represented in the column which will start by using "-" for each element. Here I've experimented with two options.

# File: hello.yml
 - name: List variables from ansible playbook
   hosts: localhost
   gather_facts: no
   vars:
     mylearning_list: ['Linux','git','Jenkins','Docker','Kubernetes','Ansible']
   tasks:
     - name: printing list
       debug:
         msg:
         - "mylearning_list:"
         - "{{  mylearning_list  }}"

     - name: Concatenate a list to string
       set_fact:
         my_string: "{{ mylearning_list | join(',') }}"
     - name: Print the String
       debug:
         msg: "{{ my_string }}"

     - name: printing list element
       debug:
         msg: "mylearning_list: {{  mylearning_list[1] }}"
     - name: printing list range of elements
       debug:
         msg:
         - "mylearning_list[3:5]:"
         - "{{  myle

Ansible list of element usage 

Ansible  list example 02

 hosts: localhost
  gather_facts: no
  vars:
    devops_team:
      - srinu
      - rajshekhar
      - arun
      - charan
      - suresh
      - elavarsi

  tasks:
  - name: Display all elements of List
    debug:
      msg: "{{ devops_team }}"

  - name: Display a elements of List
    debug:
        msg: "{{ devops_team[3] }}"

  - name: Display rage of elements from List
    debug:
        msg: "{{ devops_team[3:6] }}"
~

Ansible Dictionaries

The python dictionaries can be used in the Ansible plays. The representation is within {} when we have few key:value
The data item will be stored with key and value

We can dfine a dictionary variable as two forms : 1. single line

osfam_web: {"el": "httpd", "ubuntu": "apache2"}

2. multiline form

osfam_web:
  el: httpd 
  ubuntu: apache2

Example Execution

[ansible@master qa]$ cat mydict.yml
---
# Filename: mydict.yml
 - name: Dictionaries in ansible
   hosts: localhost
   gather_facts: false
   vars:
     osfam: {"el":"httpd","ubuntu":"apache2"}
   tasks:
     - debug:
         msg:
           - "osfam.keys {{ osfam.keys() }}"
           - "osfam {{ osfam }}"
           - "osfam type {{ osfam |type_debug }}"
           - "osfam[el] {{ osfam['el'] }}"

Execution output

ansible-playbook mydict.yml

More variable stories on Ansible Automations are share:

1. host_vars and group_vars
2. Jinja2 template variables
3. Ansible custom roles and variables