Issue while using lineinfile module - Ansible

Question

I used this solution according to my problem statement - https://www.edureka.co/community/35835/lineinfile-module-in-ansible

it worked fine for the first time but when I executed it again it gave a weird unexpected output

Before executing the playbook

#legos

After 1st execution

legos

After 2nd execution

legos
legos

After 3rd execution

legos
legos
legos

Answer 1

The lineinfile task has to match both the commented and uncommented state of the line. This way it will uncomment #lego but will pass lego unchanged.

This task should do what you want:

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