# Regex-match-scan-grep-methods ## Objectives * Use the `match` method * Use capture groups * Use the `scan` method * Understand the diff between `match` and `scan` ## Ruby Methods with Regex You've learned the basics of writing Regular Expressions in Ruby. In this lesson we'll learn how to use regular expressions with the `match` and `scan` ruby methods. We'll also learn to use capture groups. ### Scan The `scan` method returns an array of **all** items in your string that match a given Regular Expression. For example: ``` "The rain in Spain lies mainly in the plain".scan(/\w+ain/) => ["rain", "Spain", "main", "plain"] ``` ### Match The `match` method returns the first item in your string that matches a given Regular Expression as a `MatchData` object. For example: ``` "The rain in Spain lies mainly in the plain".match(/\w+ain/) => # "The rain in Spain lies mainly in the plain".match(/France/) => nil ``` More often than not, we use the result of the match method as a boolean, indicating the existence of the pattern in the given string. ### Grep Grep is an enumerable method for pattern searching in arrays and hashes. Similar to `scan`, `grep` will return an array of matching items from an array. ``` names = ["Jeri Faria", "Althea Voth", "Audry Donoho", "Scotty Chaves", "Lance Barrio", "Zachary Newhall", "Stefany Janey", "Tressie Kinsel", "Raven Grimsley", "Marketta Gaylor", "Leota Crowe", "Mazie Norman", "Damien Loffredo"] #Get items from array where first name has five letters: names.grep(/^\w{5}\s/) => ["Audry Donoho", "Lance Barrio", "Raven Grimsley", "Leota Crowe", "Mazie Norman"] ``` ### Capture Groups Using parentheses in our regex allows us to create 'groups' that we can refer to in our scan/match/grep methods as indexes in an array. In the example below we create three capture groups for the three sets of digits in a phone number. Now, when we scan a list of numbers, each phone number is broken down into subgroups based on the capture groups we built in our regular expressions: ``` numbers = "202-555-0192 202-555-0147 202-555-0131 202-555-0116 202-555-0192 202-555-0197" number_breakdown = numbers.scan(/(\d+)-(\d+)-(\d+)/) => [["202", "555", "0192"], ["202", "555", "0147"], ["202", "555", "0131"], ["202", "555", "0116"], ["202", "555", "0192"], ["202", "555", "0197"]] number_breakdown[0] => ["202", "555", "0192"] number_breakdown[0][1] => "555" ``` View [Ruby Methods with Regex](https://learn.co/lessons/regex-match-scan-grep-methods-readme) on Learn.co and start learning to code for free. View [Ruby Methods with Regex](https://learn.co/lessons/regex-match-scan-grep-methods-readme) on Learn.co and start learning to code for free. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://certil-remy.gitbook.io/learn/ruby/untitled-3.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.