Ansible lineinfile is not changing file as expect - ansible

Question

THi, new to this. . . .
Testing out a Ansible play to update the swappiness setting on a test box.
---
- hosts: "{{ target }}"
become: yes
tasks:
- name: swapness
lineinfile:
path: /etc/sysctl.conf
state: present
regexp: vm.swappiness=*
line: vm.swappiness=6
Currently, it is set to vm.swappiness=4 but running the above does not change that.
the way I read the logic is...
look for a line with "vm.swappiness=" and replace it with "vm.swappiness=6"

Answer 1

I would do in this way:
---
- name: Playbook who modify swapiness.
hosts: "{{ target }}"
become: yes
tasks:
# Set vm.swappiness to 6 in /etc/sysctl.conf
- name: Set swapiness.
sysctl:
name: vm.swappiness
value: '6'
state: present
sysctl_set: yes
reload: yes
The reason for that is that If exists any module for it, you should be doing using that module specific instead a generic one.
Ansible has a sysctl module, so it's better to use it for this.
Note: Please, review the code and set 2 white spaces between them if not already.

Answer 2

Given the file
shell> cat sysctl.conf
vm.swappiness=4
The task below works as expected
- lineinfile:
path: sysctl.conf
regexp: vm.swappiness=*
line: vm.swappiness=6
Running the playbook with the options --check --diff gives abridged
TASK [lineinfile] *****************************************************
--- before: sysctl.conf (content)
+++ after: sysctl.conf (content)
## -1 +1 ##
-vm.swappiness=4
+vm.swappiness=6
Notes
The regexp vm.swappiness=* is probably not what you really want. This regexp matches the string vm.swappiness followed by 0 or mode =. For example, below are strings that match this regexp
vm.swappiness
vm.swappiness=
vm.swappiness==========
Instead, you want a regexp that matches the string vm.swappiness= followed by 0 or more characters. For example vm.swappiness=.*