How to append to a list in Ansible

In this repository you can find examples of how to append things to lists in Ansible.

The original blog post can be found at: https://blog.crisp.se/2016/10/20/maxwenzin/how-to-append-to-lists-in-ansible

The examples make use of the builtin set_fact module.

How to run demonstration

ansible-playbook demo-append-list.yml

or (if the file is made executable)

./demo-append-list.yml

Example output

max@max-x1:~/ansible-append-list$ ansible-playbook demo-append-list.yml
 [WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'


PLAY [localhost] *******************************************************************************************************************************************************************************************

TASK [Gathering Facts] *************************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "msg": "Append list to list, or merge two lists"
}

TASK [Setup two lists to be merged] ************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "list_one": [
        1,
        2,
        3
    ]
}

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "list_two": [
        4,
        5,
        6
    ]
}

TASK [Merge the two lists] *********************************************************************************************************************************************************************************
ok: [localhost]

TASK [Demonstrate merged lists] ****************************************************************************************************************************************************************************
ok: [localhost] => {
    "lists_merged": [
        1,
        2,
        3,
        4,
        5,
        6
    ]
}

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "msg": "Append/merge list of maps to list"
}

TASK [Setup two lists to be merged] ************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "list_one": [
        {
            "first_name": "John",
            "last_name": "Doe"
        },
        {
            "first_name": "Jane",
            "last_name": "Doe"
        }
    ]
}

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "list_two": [
        {
            "first_name": "Douglas",
            "last_name": "Adams"
        },
        {
            "first_name": "Frederic",
            "last_name": "Bastiat"
        }
    ]
}

TASK [Merge the two lists of maps] *************************************************************************************************************************************************************************
ok: [localhost]

TASK [Demonstrate merged lists] ****************************************************************************************************************************************************************************
ok: [localhost] => {
    "lists_merged": [
        {
            "first_name": "John",
            "last_name": "Doe"
        },
        {
            "first_name": "Jane",
            "last_name": "Doe"
        },
        {
            "first_name": "Douglas",
            "last_name": "Adams"
        },
        {
            "first_name": "Frederic",
            "last_name": "Bastiat"
        }
    ]
}

TASK [Initialize an empty list] ****************************************************************************************************************************************************************************
ok: [localhost]

TASK [Setup a integer variable] ****************************************************************************************************************************************************************************
ok: [localhost]

TASK [Append item to list] *********************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "the_list": [
        5
    ]
}

TASK [Append another item to the list] *********************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "the_list": [
        5,
        6
    ]
}

TASK [Initialize an empty list for our truths] *************************************************************************************************************************************************************
ok: [localhost]

TASK [Setup a boolean variable] ****************************************************************************************************************************************************************************
ok: [localhost]

TASK [Append boolean to list] ******************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "my_thruths": [
        true
    ]
}

TASK [Append another boolean to the list] ******************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "my_thruths": [
        true,
        false
    ]
}

TASK [Initialize an empty list for our strings] ************************************************************************************************************************************************************
ok: [localhost]

TASK [Setup a string variable] *****************************************************************************************************************************************************************************
ok: [localhost]

TASK [Append string to list] *******************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "my_strings": [
        "Max"
    ]
}

TASK [Append another item to the list] *********************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "my_strings": [
        "Max",
        "Power"
    ]
}

PLAY RECAP *************************************************************************************************************************************************************************************************
localhost                  : ok=31   changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Ansible version

Demo built with Ansible version 2.6.5 Tested up to version 2.10.8