This guide will walk through how to use grep instead of other methods in Ruby, such as select and map to search through a collection.

To start with, I'm going to create an array of file names.

arr = ['hey.rb', 'there.rb', 'index.html']

Now let's see how we can use grep to perform the functions of select or map.

First, let's say, you want to return only the files that end in the extension .rb, and along with it, you want to remove the extension, so the output has only file names.

The typical code to implement this type of behavior would be something like:

p arr.select { |x| x=~ /\.rb/ }.map{ |x| x[0..-4]}

The output should have just the values ["hey", "there"].

Though that worked, we can make it more efficient by using the grep method. By leveraging grep our code can be consolidated down to:

arr.grep(/(.*)\.rb/){$1}

The output will be the same.

devCamp Note: The {$1} is a tool that you can use regular expression matchers in Ruby to capture the values that were matched. So in our example the actual values that were matched were hey and there. The .rb was left off by default because it was not part of the match value that was returned. Ruby borrowed this concept from the Perl programming language.