Ansible the lineinfile, blockinfile and replace modules

 Hello !!

This post is for exploring the "lineinfile" vs 'blockinfile' and "replace" modules. The replace and the lineinfile use the path parameter to mark: The file to modify. lineinfile module is used to ensure[s] a particular line is in a file, or [to] replace an existing line using a back-referenced (backref) regular expression (regex).

Use the replace module if you want to change multiple, similar lines

The "dest" parameter is used for modules creating new files like template or copy modules. Just replace dest with path and both provided examples should work as expected.

Adding lines in the file

Adding a line in a file, if a file does not exist then it will create it.

---
# Filename: adding_line.yml
 - name: testing LineInFile module
   hosts: localhost
   tasks:
   - name: Add a line to a file if the file does not exist
     lineinfile:
       path: /tmp/hosts
       line: 192.168.1.99 ansiblectl.devopshunter.com ctl
       create: yes

The execution of the above playbook gives us the, update of the file /tmp/hosts file created with the line value. check the content of the file.

 
Screenshot 1

Adding a line in file create if not 

Insert before 

A line can be inserted before the pattern matched 

---
 - name: testing inline
   hosts: localhost
   gather_facts: no
   tasks:
   - name: insert before
     lineinfile:
       dest: /tmp/hosts
       line: 192.168.0.19 bhagathsing.devops.com bhagathsing
       insertbefore: (192.168.0.18*)
  

Execution will gives as follows:

Ansible the lineinfile module using insertbefore parameter

Insert After

Insert after the pattern line

---
 - name: testing inline
   hosts: localhost
   gather_facts: no
   tasks:
   - name: insert after
     lineinfile:
       dest: /tmp/hosts
       line: 192.168.0.18 freedome.devops.com freedome
       insertafter: (192.*)
  

lineinfile module with 'insertafter' parameter

 Removal lines in a file of httpd.conf

---
 - name: testing inline
   hosts: localhost
   gather_facts: no
   tasks:
   - name: remove commented lines
     lineinfile:
      dest: /tmp/sample
      regex: "(^#)"
      state: absent
      backup: yes
   - name: remove tabbed commented lines
     lineinfile:
      dest: /tmp/sample
      regex: "(#)"
      state: absent
   - name: remove blank lines
     lineinfile:
      dest: /tmp/sample
      regex: "(^\n)"
      state: absent   

The execution of removal of lines from the httpd.conf file.

The lineinfile module uses to remove comment lines of httpd.conf file

Replace module

This module will be helps you to find and replace the text in remote/target server files.

 /tmp/mytest.txt 

Step 2: Create a playbook with the File name: test-replace.yml and the content as follows
---
# Ansile replace module example
 - name: Ansile replace module
   gather_facts: no
   hosts: localhost
   become: yes
   tasks:
     - name: mytest.txt replace
       replace:
         path: /tmp/mytest.txt
         regexp: "ofmw"
         replace: "Oracle Fusion Middleware"


		 
Assume that you have inventory file having 'webserver' group with node1, node2


Step 3: Execution output is as follows:
ansible-playbook test-replace.yml                                                                                                                             

Execution Screen shots: 

'blockinfile' module

If you have multiple lines that need to be inserted into a file in remote box with Ansible blockinfile module. It works similar ot lineinfile module but here multiple lines can be processed.

--- 
# Filename: file-blocking.yaml
# targets [optional] if you pass extra vars ok, otherwise localhost
- name: Creating File with blockinfile
  gather_facts: no
  hosts: "{{ targets | default('localhost') }}"

  tasks:
  - name: Create new file
    file:
      path: /tmp/ansible-slogun.txt
      state: touch
    
  - name: Block of text adds to file
    blockinfile:
      path: /tmp/ansible-slogun.txt
      block: Ansible has a large collection of inbuilt modules to manage various cloud resources. The book begins with the concepts needed to safeguard your credentials and explain how you interact with cloud providers to manage resources. Each chapter begins with an introduction and prerequisites to use the right modules to manage a given cloud provider. Learn about Amazon Web Services, Google Cloud, Microsoft Azure, and other providers.

The playbook can be using no extra vars that means localhost will be target host, the executed as follows :

ansible-playbook file-blocking.yaml

References:

1. Official Documentation link
2. The joy of the blockinfile