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ansible
dmzkrsk
dmzkrsk

Reputation: 2115

Ansible: check, that file has changed after shell command

I have a shell command in ansible, that changes some file. But most of the time, file stays the same.

What is a preferred way to compare the content of the file before/after shell command and set task changed property?

Upvotes: 1

Views: 1434

Answers (1)

Vladimir Botka
Vladimir Botka

Reputation: 67984

Q: "Compare the content of the file before/after the shell command and set task changed."

A: Make the script report the changes, register the output of the shell command, and test changed_when.

For example, the task below sets a random environment variable RANDOM_TEXT and writes it to the file /tmp/test.ansible. If the file changes the script will report changed. Because of the potentially failing diff you have to set ignore_errors: true

    - shell: "sh -c 'cp /tmp/test.ansible /tmp/test.ansible.orig;
                     echo $RANDOM_TEXT > /tmp/test.ansible;
                     if (diff /tmp/test.ansible.orig /tmp/test.ansible > /dev/null);
                     then echo not changed;
                     else echo changed;
                     fi'"
      environment:
        RANDOM_TEXT: "{{ lookup('random_choice', 'AAA', 'BBB') }}"
      ignore_errors: true
      register: result
      changed_when: result.stdout == 'changed'

Example of a complete playbook for testing

- hosts: localhost

  tasks:

    - shell: "sh -c 'cp /tmp/test.ansible /tmp/test.ansible.orig;
                     echo $RANDOM_TEXT > /tmp/test.ansible;
                     if (diff /tmp/test.ansible.orig /tmp/test.ansible > /dev/null);
                     then echo not changed;
                     else echo changed;
                     fi'"
      environment:
        RANDOM_TEXT: "{{ lookup('random_choice', 'AAA', 'BBB') }}"
      ignore_errors: true
      register: result
      changed_when: result.stdout == 'changed'

    - debug:
        var: result

Upvotes: 1

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