The replace module can be used to replace markup in a file on the managed node (e.g. the target system). Or, the following can be used to invoke this module on the control node (that's your Ansible server). 

• local_action module
• delegate_to parameter
• connection parameter
• hostvars magic variable

The ansible-doc replace command can be used to show the Ansible documention on the replace module.

Let's say /tmp/foo.txt contains the following text.

Hello World
Earth Hello

In this example, Hello will be replaced with Goodby in foo.txt.

- name: replace Hello with Goodbye in foo.txt
  replace:
    path: /tmp/foo.txt
    regexp: Hello
    replace: Goodbye

foo.txt should now have the following.

Goodbye World
Earth Goodbye

regular expression (regexp)

Regular expressions can be used. In this example, only lines beginning with Hello will be replaced with Goodbye.

- name: replace lines beginning with Hello with Goodbye in foo.txt
  replace:
    path: /tmp/foo.txt
    regexp: ^Hello
    replace: Goodbye

If the file was successfully updated, the play should indicate changed.

TASK [replace lines beginning with 'Hello' followed by anything with 'World' in foo.txt]
changed: [server1.example.com]

If the file was not updated, the play should indicate ok. This is the expected behavior if there are no lines to replace in the file.

TASK [replace lines beginning with 'Hello' followed by anything with 'World' in foo.txt]
ok: [server1.example.com]