Ansible set_fact array and populate it from in loop

Ansible set_fact array and populate it from in loop

To populate an array using Ansible's set_fact and iterate over items to fill it, you can use a loop in Ansible tasks. Here's how you can achieve this:

Example Playbook

Assume you want to create an array of filenames from a list of files retrieved from a directory on a remote host.

--- - name: Populate array using set_fact hosts: your_target_host gather_facts: no # Disable gathering facts to speed up execution tasks: - name: List files in a directory shell: ls /path/to/your/directory register: files_result - name: Initialize an empty array set_fact: file_array: [] - name: Populate array with filenames set_fact: file_array: "{{ file_array + [ item ] }}" loop: "{{ files_result.stdout_lines }}" - name: Display populated array debug: var: file_array

Explanation:

  1. List files in a directory: Uses the shell module to list files in /path/to/your/directory on the remote host and stores the result in files_result.

  2. Initialize an empty array: Initializes an empty array file_array using set_fact.

  3. Populate array with filenames: Iterates over files_result.stdout_lines (which contains the list of filenames) using a loop and appends each filename to file_array.

    • file_array: "{{ file_array + [ item ] }}": Constructs a new array by concatenating the existing file_array with the current item (filename).

  4. Display populated array: Uses the debug module to display the file_array after it has been populated.

Notes:

  • gather_facts: no: Disabling gather_facts speeds up playbook execution if you don't need other facts about the remote host.

  • Looping with set_fact: Ansible allows you to loop over items and modify facts dynamically using set_fact. This is useful for scenarios where you need to construct data structures based on dynamic information retrieved during playbook execution.

  • Adjust Path: Replace /path/to/your/directory with the actual path on your remote host where you want to list files.

This example demonstrates how to populate an array (file_array) in Ansible using set_fact and a loop (loop) over items obtained from a previous task (files_result). Adjust the playbook according to your specific use case and data retrieval requirements.

Examples

  1. Ansible set_fact array and populate from loop Description: Initialize an empty array in Ansible, iterate over a list, and append values to the array using a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Populate array with values from loop set_fact: my_array: "{{ my_array + [item] }}" loop: - value1 - value2 - value3 - debug: var: my_array

    Explanation: In this Ansible playbook example, my_array is initialized as an empty list. The set_fact task iterates over a list of items (value1, value2, value3) and appends each item to my_array. Finally, the debug task prints the contents of my_array.

  2. Ansible set_fact array from loop with condition Description: Populate an array in Ansible only if certain conditions are met within a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Populate array with values from loop with condition set_fact: my_array: "{{ my_array + [item] }}" loop: - value1 - value2 - value3 when: item != 'value2' - debug: var: my_array

    Explanation: Here, the set_fact task appends each item (value1, value2, value3) to my_array, but only if the condition when: item != 'value2' is true. my_array will contain value1 and value3 after execution.

  3. Ansible set_fact array from file contents Description: Populate an array in Ansible with values read from a file using a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Read file contents into array set_fact: my_array: "{{ my_array + [item] }}" with_lines: cat /path/to/file.txt - debug: var: my_array

    Explanation: This playbook reads each line from /path/to/file.txt and appends it to my_array using the with_lines loop. The debug task then displays the contents of my_array.

  4. Ansible set_fact array from registered variable Description: Populate an array in Ansible with values from a registered variable using a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Get list of files find: paths: /path/to/directory patterns: "*.txt" register: file_list - name: Populate array with file names set_fact: my_array: "{{ my_array + [item.path] }}" loop: "{{ file_list.files }}" - debug: var: my_array

    Explanation: This playbook uses the find module to retrieve a list of .txt files in /path/to/directory and registers the result in file_list. Then, it iterates over file_list.files and appends each file path (item.path) to my_array, which is then displayed using debug.

  5. Ansible set_fact array with nested loops Description: Populate an array in Ansible using nested loops to concatenate multiple lists.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Outer loop set_fact: inner_array: [] with_items: - value1 - value2 - name: Inner loop set_fact: inner_array: "{{ inner_array + [item + '_sub'] }}" with_items: "{{ inner_array }}" loop_control: loop_var: item - name: Append inner_array to my_array set_fact: my_array: "{{ my_array + inner_array }}" - debug: var: my_array

    Explanation: In this example, the outer loop (with_items) iterates over value1 and value2. Inside the outer loop, an inner loop (with_items) appends _sub to each item in inner_array. After processing both loops, inner_array is appended to my_array, and the result is displayed using debug.

  6. Ansible set_fact array with condition inside loop Description: Populate an array in Ansible and apply a condition to each item within a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Populate array with filtered values set_fact: my_array: "{{ my_array + [item] }}" loop: - value1 - value2 - value3 when: item != 'value2' - debug: var: my_array

    Explanation: This playbook demonstrates how to populate my_array with values (value1, value2, value3) from the loop, applying a condition (when: item != 'value2') to exclude 'value2' from being added to my_array. The resulting array is then displayed using debug.

  7. Ansible set_fact array with dictionary values Description: Populate an array in Ansible with values extracted from dictionary items using a loop.

    --- - hosts: localhost gather_facts: false vars: my_dict: key1: value1 key2: value2 key3: value3 my_array: [] tasks: - name: Populate array with dictionary values set_fact: my_array: "{{ my_array + [item.value] }}" loop: "{{ my_dict | dict2items }}" - debug: var: my_array

    Explanation: This playbook initializes my_dict with key-value pairs. The set_fact task iterates over my_dict converted to items (dict2items filter) and appends each value (item.value) to my_array. Finally, my_array is displayed using debug.

  8. Ansible set_fact array with conditional append Description: Populate an array in Ansible and conditionally append values based on a loop.

    --- - hosts: localhost gather_facts: false vars: my_array: [] tasks: - name: Populate array with conditional values set_fact: my_array: "{{ my_array + [item] }}" loop: - value1 - value2 - value3 when: item != 'value2' - debug: var: my_array

    Explanation: This playbook sets my_array as an empty list and uses the set_fact task to append each item (value1, value2, value3) to my_array, excluding 'value2' based on the condition when: item != 'value2'. The resulting array is then printed using debug.

  9. Ansible set_fact array with filtered values Description: Populate an array in Ansible with values filtered from a list using a loop.

    --- - hosts: localhost gather_facts: false vars: my_list: - value1 - value2 - value3 my_array: [] tasks: - name: Populate array with filtered values set_fact: my_array: "{{ my_array + [item] }}" loop: "{{ my_list }}" when: item != 'value2' - debug: var: my_array

    Explanation: This playbook initializes my_list with values (value1, value2, value3). The set_fact task iterates over my_list and appends each item (item) to my_array, excluding 'value2' based on the condition when: item != 'value2'. The resulting array is then displayed using debug.

  10. Ansible set_fact array with dynamic values Description: Populate an array in Ansible with dynamically generated values using a loop.

    --- - hosts: localhost gather_facts: false vars: count: 5 my_array: [] tasks: - name: Populate array with dynamic values set_fact: my_array: "{{ my_array + [ 'value' + item | string ] }}" loop: "{{ range(1, count+1) | list }}" - debug: var: my_array

    Explanation: This playbook uses the range function to generate a list (1 to count) and iterates over it (loop). Each item in the loop is converted to a string ('value' + item | string) and appended to my_array using the set_fact task. Finally, my_array is printed using debug.

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