Looping through a register variable

[Dimitri Yioulos]

Good day, all. I hope I'm not wearing out my welcome with too many questions.

In the following playbook, I first find any know_host file for any user on a particular system. I then copy a file with the list of additions to add to the known_hosts files. What I want to do is use the output of my register values to make changes to those know_host files, which my last play does. My iteration is wrong, though.

The playbook:

---

- hosts: all
  gather_facts: false
  become: yes

  vars:
    script_path: <script>

  tasks:

    - name: Find known hosts
      shell: find /root /home -type f -name known_hosts
      register: known

    - name: Debug known_hosts paths
      debug:
        msg: "{{ known.stdout }}"

    - name: Set fact with known_hosts paths
      set_fact:
        known_hosts_paths: "{{ known.stdout_lines }}"

    - name: Upload entries for new known_hosts svn
      copy:
        src: append
        dest: /tmp/append
        owner: root
        group: root
        mode: u=rwx,g=rw,o=rw

    - name: Append to all known_host files
      shell: cat /tmp/append >> {{ item }}
      loop:
        - '{{ known.stdout }}'

The output of the first play:

ok: [myhost] =>
  msg: |-
    /root/.ssh/known_hosts
    /home/user1/.ssh/known_hosts
    /home/ user2/.ssh/known_hosts
    /home/ user3/.ssh/known_hosts
    /home/ user4/.ssh/known_hosts

How do I make that last play work?

[Todd Lewis]

You want stdout_lines rather than stdout. The former is a list with new-lines removed. The latter is a possibly very long string with the complete output stream intact.

    - name: Append to all known_host files
      shell: cat /tmp/append >> {{ item }}
      loop:
        - '{{ known.stdout_lines }}'

How do I make that last play work? --
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-- 
Todd

[Dimitri Yioulos]

Todd, I made the change, but, the last play failed:

TASK [Append to all known_host files] *****************************************************************************************************
Thursday 23 May 2024  11:06:33 -0400 (0:00:01.629)       0:00:06.012 **********
Thursday 23 May 2024  11:06:33 -0400 (0:00:01.629)       0:00:06.011 **********
failed: [myhost] (item=['/root/.ssh/known_hosts', '/home/user1/.ssh/known_hosts', '/home/user2/.ssh/known_hosts', '/home/user3/.ssh/known_hosts', '/home/user4/.ssh/known_hosts']) => changed=true
  ansible_loop_var: item
  cmd: cat /tmp/append >> ['/root/.ssh/known_hosts', '/home/user1/.ssh/known_hosts', '/home/user2/.ssh/known_hosts', '/home/user3/.ssh/known_hosts', '/home/user4/.ssh/known_hosts']
  delta: '0:00:00.012330'
  end: '2024-05-23 11:06:33.947617'
  item:
  - /root/.ssh/known_hosts
  - /home/user1/.ssh/known_hosts
  - /home/user2/.ssh/known_hosts
  - /home/user3/.ssh/known_hosts
  - /home/user4/.ssh/known_hosts
  msg: non-zero return code
  rc: 1
  start: '2024-05-23 11:06:33.935287'
  stderr: '/bin/sh: line 1: [/root/.ssh/known_hosts,: No such file or directory'
  stderr_lines: <omitted>
  stdout: ''
  stdout_lines: <omitted>

I wonder if [ in  [/root/.ssh/known_hosts is getting in the way, since  /root/.ssh/known_host does exist.

[Todd Lewis]

Gah! Of course. known.stdout_lines is a list, so

loop:
  - '{{ known.stdout_lines }}'

passes the whole list as a single item. So you need to not put the list in a list:

loop: '{{ known.stdout_lines }}'

should do the trick.
—
Todd

To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/48b522d1-3503-4606-958b-29ab38398f5en%40googlegroups.com.

-- 
Todd

[Dimitri Yioulos]

Yupper, that worked. And, I appreciate the explanation. As the Farber College motto states, "Learning is Good".

[Dick Visser]

Sent from Gmail Mobile

On Thu, May 23, 2024 at 16:50 Todd Lewis <uto...@gmail.com> wrote:

You want stdout_lines rather than stdout. The former is a list with new-lines removed. The latter is a possibly very long string with the complete output stream intact.

    - name: Append to all known_host files
      shell: cat /tmp/append >> {{ item }}
      loop:
        - '{{ known.stdout_lines }}'

That should probably just loop over the list itself? So:

    - name: Append to all known_host files
      shell: cat /tmp/append >> {{ item }}
      loop: '{{ known.stdout_lines }}'

To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/4b07b147-2d6b-40d4-aa6f-a0e385893c6a%40gmail.com.

[Rowe, Walter P. (Fed)]

Here is an illustration of the difference for those interested.

- name: test loop constructs

  hosts: localhost

  gather_facts: false

  become: false

  vars:

    my_list: [ one, two, three ]

  tasks:

    - name: construct 1

      debug: var=item

      loop:

        - '{{ my_list }}'

    - name: construct 2

      debug: var=item

      loop: '{{ my_list }}'

% ansible-playbook -i localhost, loop.yml

PLAY [test loop constructs] ********************************************************************************************

TASK [construct 1] *****************************************************************************************************

ok: [localhost] => (item=['one', 'two', 'three']) => {

    "ansible_loop_var": "item",

    "item": [

        "one",

        "two",

        "three"

    ]

}

TASK [construct 2] *****************************************************************************************************

ok: [localhost] => (item=one) => {

    "ansible_loop_var": "item",

    "item": "one"

}

ok: [localhost] => (item=two) => {

    "ansible_loop_var": "item",

    "item": "two"

}

ok: [localhost] => (item=three) => {

    "ansible_loop_var": "item",

    "item": "three"

}

PLAY RECAP *************************************************************************************************************

localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

Walter
--
Walter Rowe, Division Chief
Infrastructure Services Division
Mobile: 202.355.4123

On May 24, 2024, at 7:41 AM, Rowe, Walter P. (Fed) <walte...@nist.gov> wrote:

Very subtle but very different. Great catch Todd.

In the first instance you create a list that contains a single item – another list called known.stdout_lines.

loop:
  - '{{ known.stdout_lines }}'

In the second instance you provide a list called known.stdout_lines as the list for the loop:

loop: '{{ known.stdout_lines }}'

The second instance is the desired behavior. The difference is subtle at first glance but makes a world of difference in execution.

Walter
--
Walter Rowe, Division Chief
Infrastructure Services Division
Mobile: 202.355.4123

To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/b661295c-91dd-449f-ad73-d1eb4a60f7a1%40gmail.com.

[Rowe, Walter P. (Fed)]

Very subtle but very different. Great catch Todd.

In the first instance you create a list that contains a single item – another list called known.stdout_lines.

loop:
  - '{{ known.stdout_lines }}'

In the second instance you provide a list called known.stdout_lines as the list for the loop:

loop: '{{ known.stdout_lines }}'

The second instance is the desired behavior. The difference is subtle at first glance but makes a world of difference in execution.

Walter
--
Walter Rowe, Division Chief
Infrastructure Services Division
Mobile: 202.355.4123

On May 23, 2024, at 11:30 AM, Todd Lewis <uto...@gmail.com> wrote:

To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/b661295c-91dd-449f-ad73-d1eb4a60f7a1%40gmail.com.