ansible diff module example between two files,Using Ansible Diff Module: A Detailed Guide to Comparing Two Files

Using Ansible Diff Module: A Detailed Guide to Comparing Two Files

Ansible, a powerful IT automation tool, offers a variety of modules to simplify various tasks. One such module is the diff module, which is particularly useful for comparing two files. Whether you’re a system administrator or a developer, understanding how to use the diff module can save you time and effort. In this article, I’ll walk you through the process of using the diff module to compare two files in Ansible. Let’s dive in!

Understanding the Diff Module

The diff module in Ansible is designed to compare two files and display the differences between them. It can be used to compare files on the same host or across different hosts. The module returns a non-zero exit code if the files differ, making it easy to integrate with other Ansible modules and playbooks.

Prerequisites

Before you start using the diff module, ensure that you have the following prerequisites in place:

• Ansible installed on your system
• Access to the hosts where you want to compare the files
• Two files to compare

Basic Syntax

The basic syntax for the diff module is as follows:

diff:  path/to/source/file: path/to/destination/file

In this syntax, “path/to/source/file” is the path to the source file, and “path/to/destination/file” is the path to the destination file you want to compare it with.

Comparing Files on the Same Host

Let’s say you have two files, “file1.txt” and “file2.txt,” on the same host. You want to compare these files using the diff module. Here’s how you can do it:

- name: Compare two files on the same host  diff:    path/to/file1.txt: path/to/file2.txt

This playbook will compare the contents of “file1.txt” and “file2.txt” and display the differences if any.

Comparing Files Across Different Hosts

Suppose you have two files, “file1.txt” on host1 and “file2.txt” on host2. You want to compare these files using the diff module. Here’s how you can do it:

- name: Compare two files across different hosts  hosts: all  tasks:    - name: Compare files on host1      diff:        path/to/file1.txt: path/to/file2.txt      register: diff_result    - name: Compare files on host2      diff:        path/to/file1.txt: path/to/file2.txt      register: diff_result2    - name: Check if the files are the same      assert:        that: diff_result.stdout == diff_result2.stdout

This playbook compares the contents of “file1.txt” and “file2.txt” on both host1 and host2. If the files are the same, the assert module will pass; otherwise, it will fail.

Output of the Diff Module

The diff module returns the differences between the two files in the following format:

--- path/to/source/file+++ path/to/destination/file@@ @@...

This output shows the differences between the two files. You can use this output to identify the changes made to the files.

Customizing the Output

By default, the diff module displays the differences in a unified format. However, you can customize the output format using the “output” parameter. Here’s an example:

- name: Customize the output format  diff:    path/to/source/file: path/to/destination/file    output: patch

This playbook will generate a patch file containing the differences between the two files.

Conclusion

Using the diff module in Ansible can be a valuable tool for comparing files on the same or different hosts. By following the steps outlined in this article, you can easily compare files and identify the differences between them. Whether you’re a system administrator or a developer, the diff module can help you save time and effort in your day-to-day tasks.