#                 
## Overview
We can check if a certain key is present in our environment variables using the **`has_key()` method** in Ruby. This method is invoked on the `ENV` class.

## Syntax
```ruby
ENV.has_key(name)
```
## Parameters
**`name`**: This is the name of each environment variable that we want to check to see if it is present.
## Return value
The value returned is a Boolean. If the key exists, then `true` is returned. Otherwise, `false` is returned.
## Example



# create some environment variables
ENV["platform"] = "Edpresso"
ENV["isBest"] = "true"
ENV["user_key"] = "1234skldks"

# check if some environment variables exist
puts ENV.has_key?("user_key")  # true
puts ENV.has_key?("isBest")    # true
puts ENV.has_key?("platform")  # true
puts ENV.has_key?("foo")       # false
puts ENV.has_key?("bar")       # false

## Explanation
* Line 2–4: We create some environment variables.
* Line 7–11: Using the `has_key()` method, we check if some environment variable names exist and then print the results to the console.

How to know if a key is present in ENV in Ruby using has_key()

Use Ruby's `ENV.has_key(name)` to check if an environment variable key exists, returning a Boolean.