Safer Commands with argv in Ansible: Pros, Cons, and Real Examples

When using Ansible to automate tasks, the command module is your bread and butter for executing system commands. But did you know that there’s a safer, cleaner, and more predictable way to pass arguments? Meet argv—an alternative to writing commands as strings.

In this post, I’ll explore the pros and cons of using argv, and I’ll walk through several real-world examples tailored to web servers and mail servers.

Why Use argv Instead of a Command String?

✅ Pros

• Avoids Shell Parsing Issues: Each argument is passed exactly as intended, with no surprises from quoting or spaces.
• More Secure: No shell = no risk of shell injection.
• Clearer Syntax: Every argument is explicitly defined, improving readability.
• Predictable: Behavior is consistent across different platforms and setups.

❌ Cons

• No Shell Features: You can’t use pipes (|), redirection (>), or environment variables like $HOME.
• More Verbose: Every argument must be a separate list item. It’s explicit, but more to type.
• Not for Shell Built-ins: Commands like cd, export, or echo with redirection won’t work.

Real-World Examples

Let’s apply this to actual use cases.

🔧 Restarting Nginx with argv

- name: Restart Nginx using argv
  hosts: amedee.be
  become: yes
  tasks:
    - name: Restart Nginx
      ansible.builtin.command:
        argv:
          - systemctl
          - restart
          - nginx

📬 Check Mail Queue on a Mail-in-a-Box Server

- name: Check Postfix mail queue using argv
  hosts: box.vangasse.eu
  become: yes
  tasks:
    - name: Get mail queue status
      ansible.builtin.command:
        argv:
          - mailq
      register: mail_queue

    - name: Show queue
      ansible.builtin.debug:
        msg: "{{ mail_queue.stdout_lines }}"

🗃️ Back Up WordPress Database

- name: Backup WordPress database using argv
  hosts: amedee.be
  become: yes
  vars:
    db_user: wordpress_user
    db_password: wordpress_password
    db_name: wordpress_db
  tasks:
    - name: Dump database
      ansible.builtin.command:
        argv:
          - mysqldump
          - -u
          - "{{ db_user }}"
          - -p{{ db_password }}
          - "{{ db_name }}"
          - --result-file=/root/wordpress_backup.sql

⚠️ Avoid exposing credentials directly—use Ansible Vault instead.

Using argv with Interpolation

Ansible lets you use Jinja2-style variables ({{ }}) inside argv items.

🔄 Restart a Dynamic Service

- name: Restart a service using argv and variable
  hosts: localhost
  become: yes
  vars:
    service_name: nginx
  tasks:
    - name: Restart
      ansible.builtin.command:
        argv:
          - systemctl
          - restart
          - "{{ service_name }}"

🕒 Timestamped Backups

- name: Timestamped DB backup
  hosts: localhost
  become: yes
  vars:
    db_user: wordpress_user
    db_password: wordpress_password
    db_name: wordpress_db
  tasks:
    - name: Dump with timestamp
      ansible.builtin.command:
        argv:
          - mysqldump
          - -u
          - "{{ db_user }}"
          - -p{{ db_password }}
          - "{{ db_name }}"
          - --result-file=/root/wordpress_backup_{{ ansible_date_time.iso8601 }}.sql

🧩 Dynamic Argument Lists

Avoid join(' '), which collapses the list into a single string.

❌ Wrong:

argv:
  - ls
  - "{{ args_list | join(' ') }}"  # BAD: becomes one long string

✅ Correct:

argv: ["ls"] + args_list

Or if the length is known:

argv:
  - ls
  - "{{ args_list[0] }}"
  - "{{ args_list[1] }}"

📣 Interpolation Inside Strings

- name: Greet with hostname
  hosts: localhost
  tasks:
    - name: Print message
      ansible.builtin.command:
        argv:
          - echo
          - "Hello, {{ ansible_facts['hostname'] }}!"

When to Use argv

✅ Commands with complex quoting or multiple arguments
✅ Tasks requiring safety and predictability
✅ Scripts or binaries that take arguments, but not full shell expressions

When to Avoid argv

❌ When you need pipes, redirection, or shell expansion
❌ When you’re calling shell built-ins

Final Thoughts

Using argv in Ansible may feel a bit verbose, but it offers precision and security that traditional string commands lack. When you need reliable, cross-platform automation that avoids the quirks of shell parsing, argv is the better choice.

Prefer safety? Choose argv.
Need shell magic? Use the shell module.

Have a favorite argv trick or horror story? Drop it in the comments below.