How to join a list of strings in Ansible?

In Ansible, I have a list of strings that I want to join with newline characters to create a string, that when written to a file, becomes a series of lines. However, when I use the join() filter, it works on the inner list, the characters in the strings, and not on the outer list, the strings themselves. Here's my sample code:

# Usage: ansible-playbook tst3.yaml --limit <GRP>
---
- hosts: all
  remote_user: root

  tasks:

  - name: Create the list
	set_fact:
		my_item: "{{ item }}"
	with_items:
	  - "One fish"
	  - "Two fish"
	  - "Red fish"
	  - "Blue fish"
	register: my_item_result

  - name: Extract items and turn into a list
	set_fact:
		my_list: "{{ my_item_result.results | map(attribute='ansible_facts.my_item') | list }}"

  - name: Examine the list
	debug:
		msg: "{{ my_list }}"

  - name: Concatenate the public keys
	set_fact:
		my_joined_list: "{{ item | join('\n') }}"
	with_items:
	  - "{{ my_list }}"

  - name: Examine the joined string
	debug:
		msg: "{{ my_joined_list }}"

I want to get output that looks like:

One fish
Two fish
Red fish
Blue Fish

What I get instead is:

TASK: [Examine the joined string] *********************************************
ok: [hana-np-11.cisco.com] => {
	"msg": "B\nl\nu\ne\n \nf\ni\ns\nh"
}
ok: [hana-np-12.cisco.com] => {
	"msg": "B\nl\nu\ne\n \nf\ni\ns\nh"
}
ok: [hana-np-13.cisco.com] => {
	"msg": "B\nl\nu\ne\n \nf\ni\ns\nh"
}
ok: [hana-np-14.cisco.com] => {
	"msg": "B\nl\nu\ne\n \nf\ni\ns\nh"
}
ok: [hana-np-15.cisco.com] => {
	"msg": "B\nl\nu\ne\n \nf\ni\ns\nh"
}

How do I properly concatenate a list of strings with the newline character?

Solution

join filter works on lists, so apply it to your list:

- name: Concatenate the public keys
  set_fact:
    my_joined_list: "{{ my_list | join('\n') }}"

---

Explanation

While my_list in your example is a list, when you use with_items, in each iterationitem is a string. Strings are treated as lists of characters, thus join splits them.

It’s like in any language: when you have a loop for i in (one, two, three) and refer to i inside the loop, you get only one value for each iteration, not the whole set.

---

Remarks

• Don’t use debug module, but copy with content to have\n rendered as newline.

• The way you create a list is pretty cumbersome. All you need is (quotation marks are also not necessary):

    - name: Create the list
      set_fact:
        my_list:
          - "One fish"
          - "Two fish"
          - "Red fish"
          - "Blue fish"