#       
## Overview
The **`File.extname()`** or **`extname()`** function of the File class in Ruby gets the extension of a file. For example, this function will return the extension of a Ruby application file `main.rb` as `.rb`.
## Syntax
```ruby
File.extname(file_name)
```
## Parameters
**`file_name`**: This is the file whose extension name we get.
## Return value
This method returns the extension of the file `file_name`.
## Code example
Let's consider an example to see this method in action.

# Create the file names
fn1 = "main.rb"
fn2 = "app.js"
fn3 = "main.java"
fn4 = "app.py"

# Get the extension names
puts File.extname(fn1)
puts File.extname(fn2)
puts File.extname(fn3)
puts File.extname(fn4)

## Explanation
* **Lines 2 to 5**: We create some file names with their respective extensions.
* **Lines 8 to 11**: We use the `File.extname()` method to get the extension of each file. Then, we print these extensions to the console with the **`puts`** method.

What is the File.extname() method in Ruby?

File.extname() in Ruby retrieves the extension of a file, e.g., "main.rb" returns ".rb".