What is the select{} method of the ENV class in Ruby?

Overview

We can use the select{} method to select some environment variables based on a condition specified in the block. This method takes a block that specifies the condition. For every name and value pair that returns true by the condition, they are added to a Hash returned by this method.

Syntax

ENV.select{|name, value| block}
Syntax for select{} method

Parameters

  • name: The name of each environment variable.
  • value: The value of each environment variable.
  • block: This is a condition. It takes name and value in a form of the two-elements array as parameters.

Return value

The value returned is a hash of name-value pairs.

Code Example

Let's look at the code below:

# clear default environment variables
ENV.clear
# create new environment variables
ENV["token"] = "12345"
ENV["base_url"] = "https://baseurl.com"
ENV["foo"] = "0"
ENV["bar"] = "1"
# select variables that starts with "b"
puts ENV.select{|name, value| name.start_with?("b") }

Explanation

In the code above,

  • Line 2: We clear the default or environment variables present.
  • Lines 5 to 8: We create the new environment variables.
  • Line 11: We use the select{} method to select environment variables that begin with the letter b.

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