Ansible lineinfile duplicates line

Question

I have a simple file at /etc/foo.txt. The file contains the following:

#bar

I have the following ansible playbook task to uncomment the line ab

Answer 1

The problem is the task's regex only matches the commented out line, #bar. To be idempotent, the lineinfile task needs to match both the commented and uncommented state of the line. This way it will uncomment #bar but will pass bar unchanged.

This task should do what you want:

- name: test lineinfile
  lineinfile: 
    backup=yes
    state=present
    dest=/etc/foo.txt
    regexp='^#?bar'
    line='bar'

Note the only change was adding a "?" to the regex.