I'm trying to execute a shell script on a localhost using Ansible and display the output of the script. I've registered the output of the command using the shell module and stored it in the result variable. When I print result using the debug module, I see the dictionary duplicated. The dictionary contains both the stdout and stdout_lines fields, but I don't understand why the result is duplicated. Here's the playbook I'm using:

yaml

---
- name: Run shell script and display all keys in result
  hosts: localhost
  tasks:
    - name: Create the shell script
      copy:
        dest: /tmp/multi_output.sh
        content: |
          #!/bin/bash
          # Print multiple messages to STDOUT
          for i in {1..101}
          do
              echo "Message $i to STDOUT"
          done
          sync  # Forces the buffer to be written to disk
        mode: '0755'

    - name: Run the shell script
      shell: "/tmp/multi_output.sh"
      register: result
      environment:
        PYTHONUNBUFFERED: 1
        
    - name: Display unique lines from 'stdout_lines'
      debug:
        var: result.stdout_lines
      changed_when: false

    - name: Display all keys in 'result'
      debug:
        var: result

Question: Why do I see two similar entries when I print result, as if the dictionary is duplicated (e.g., the stdout and stdout_lines fields)? How can I avoid this behavior and get a clear display of the output?

TASK [Visualizzare tutte le chiavi di 'result'] ********************************
ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "....",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 82 su STDOU"
}

ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "....",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 3 su STDOUT"
        ]
    }
}

TASK [Visualizzare tutte le chiavi di 'result'] ********************************
ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "...",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 3 su STDOUT"
        ]
    }
}

I'm trying to execute a shell script on a localhost using Ansible and display the output of the script. I've registered the output of the command using the shell module and stored it in the result variable. When I print result using the debug module, I see the dictionary duplicated. The dictionary contains both the stdout and stdout_lines fields, but I don't understand why the result is duplicated. Here's the playbook I'm using:

yaml

---
- name: Run shell script and display all keys in result
  hosts: localhost
  tasks:
    - name: Create the shell script
      copy:
        dest: /tmp/multi_output.sh
        content: |
          #!/bin/bash
          # Print multiple messages to STDOUT
          for i in {1..101}
          do
              echo "Message $i to STDOUT"
          done
          sync  # Forces the buffer to be written to disk
        mode: '0755'

    - name: Run the shell script
      shell: "/tmp/multi_output.sh"
      register: result
      environment:
        PYTHONUNBUFFERED: 1
        
    - name: Display unique lines from 'stdout_lines'
      debug:
        var: result.stdout_lines
      changed_when: false

    - name: Display all keys in 'result'
      debug:
        var: result

Question: Why do I see two similar entries when I print result, as if the dictionary is duplicated (e.g., the stdout and stdout_lines fields)? How can I avoid this behavior and get a clear display of the output?

TASK [Visualizzare tutte le chiavi di 'result'] ********************************
ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "....",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 82 su STDOU"
}

ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "....",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 3 su STDOUT"
        ]
    }
}

TASK [Visualizzare tutte le chiavi di 'result'] ********************************
ok: [localhost] => {
    "result": {
        "changed": true,
        "cmd": "/tmp/multi_output.sh",
        "delta": "0:00:00.016129",
        "end": "2025-03-19 17:17:17.259092",
        "failed": false,
        "msg": "",
        "rc": 0,
        "start": "2025-03-19 17:17:17.242963",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "...",
        "stdout_lines": [
            "Messaggio 1 su STDOUT",
            "Messaggio 2 su STDOUT",
            "Messaggio 3 su STDOUT"
        ]
    }
}

• ansible
• ansible-2.x
• ansible-runner

• 1 That are the Common Return Values. And when stdout is returned, Ansible always provides a list of strings, each containing one item per line from the original output. – U880D Commented Mar 19 at 19:29
• "I don't understand why the result is duplicated.", it was designed, created in that way. So either use results.stdout or result.stdout_lines depending on what you try to achieve. – U880D Commented Mar 19 at 19:33
• Furthermore, "Display all keys in 'result'" would be more var: result.keys() and resulting into an output of result.keys(): - changed - stdout - stderr - rc - cmd - start - end - delta - msg - stdout_lines - stderr_lines - failed, a list of the dict keys. – U880D Commented Mar 19 at 19:34

3 Answers 3

When you register results from the shell: module, you get the outpt twice, by design. One is the entire output in stdout key, which is a single string and the other is a list with all the lines one-by-one in the stdout_lines key. The content will be the same, you may decide which one fits better to the task you want to do with it.

By the way, you do not have to create a script file and the run it in a separate step. You can simply use the shell: module with the | operator, as you did with the copy: module.

On the last line of your code, have...

var: result.stdout

...or...

var: result.stdout_lines

...whichever you prefer.

The issue was resolved by updating the versions of the libraries to:

• ansible==4.10.0

• ansible-core==2.11.12

• ansible-runner==2.4.0

These versions are not the latest because I need to maintain compatibility with CentOS 7 systems running Python 2.7.

With this configuration, the issue no longer occurs.