Ruby | Regular Expressions Last Updated : 27 Sep, 2025 Comments Improve Suggest changes Like Article Like Report A regular expression is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings. Ruby regular expressions i.e. Ruby regex for short, helps us to find particular patterns inside a string. Two uses of ruby regex are Validation and Parsing. Ruby regex can be used to validate an email address and an IP address too. Ruby regex expressions are declared between two forward slashes. Syntax:# finding the word 'hi'"Hi there, i am using gfg" =~ /hi/ This will return the index of first occurrence of the word 'hi' if present, or else will return ' nil '. Checking if a string has a regex or notWe can also check if a string has a regex or not by using the match method. Below is the example to understand. Example : Ruby # Ruby program of regular expression # Checking if the word is present in the string if "hi there".match(/hi/) puts "match" end Output:matchChecking if a string has some set of characters or notWe can use a character class which lets us define a range of characters for the match. For example, if we want to search for vowel, we can use [aeiou] for match. Example : Ruby # Ruby program of regular expression # declaring a function which checks for vowel in a string def contains_vowel(str) str =~ /[aeiou]/ end # Driver code # Geeks has vowel at index 1, so function returns 1 puts( contains_vowel("Geeks") ) # bcd has no vowel, so return nil and nothing is printed puts( contains_vowel("bcd") ) Output:1Different regular expressionsThere are different short expressions for specifying character ranges : \w is equivalent to [0-9a-zA-Z_]\d is the same as [0-9]\s matches white space\W anything that’s not in [0-9a-zA-Z_]\D anything that’s not a number\S anything that’s not a spaceThe dot character . matches all but does not match new line. If you want to search . character, then you have to escape it.Example : Ruby # Ruby program of regular expression a="2m3" b="2.5" # . literal matches for all character if(a.match(/\d.\d/)) puts("match found") else puts("not found") end # after escaping it, it matches with only '.' literal if(a.match(/\d\.\d/)) puts("match found") else puts("not found") end if(b.match(/\d.\d/)) puts("match found") else puts("not found") end Output:match foundnot foundmatch foundModifiers for regexFor matching multiple characters we can use modifiers: + is for 1 or more characters* is for 0 or more characters? is for 0 or 1 character{x, y} if for number of characters between x and yi is for ignores case when matching text.x is for ignores whitespace and allows comments in regular expressions.m is for matches multiple lines, recognizing newlines as normal characters.u,e,s,n are for interprets the regexp as Unicode (UTF-8), EUC, SJIS, or ASCII. the regular expression is assumed to use the source encoding, If none of these modifiers is specified. Comment M ManishKhetan Follow Improve M ManishKhetan Follow Improve Article Tags : Ruby Ruby-Basics Ruby-String Explore Ruby Programming Language 4 min read OverviewRuby For Beginners 3 min read Ruby Programming Language (Introduction) 4 min read Comparison of Java with Other Programming Languages 4 min read Similarities and Differences between Ruby and C language 3 min read Similarities and Differences between Ruby and C++ 3 min read Environment Setup in Ruby 3 min read How to install Ruby on Linux? 2 min read How to install Ruby on Windows? 2 min read Interesting facts about Ruby Programming Language 2 min read BasicsRuby | Keywords 4 min read Ruby | Data Types 3 min read Ruby Basic Syntax 3 min read Hello World in Ruby 2 min read Ruby | Types of Variables 4 min read Global Variable in Ruby 2 min read Comments in Ruby 2 min read Ruby | Ranges 4 min read Ruby Literals 4 min read Ruby Directories 5 min read Ruby | Operators 11 min read Operator Precedence in Ruby 2 min read Operator Overloading in Ruby 5 min read Ruby | Pre-define Variables & Constants 5 min read Ruby | unless Statement and unless Modifier 2 min read Control StatementsRuby | Decision Making (if, if-else, if-else-if, ternary) | Set - 1 3 min read Ruby | Loops (for, while, do..while, until) 5 min read Ruby | Case Statement 3 min read Ruby | Control Flow Alteration 7 min read Ruby Break and Next Statement 2 min read Ruby redo and retry Statement 2 min read BEGIN and END Blocks In Ruby 2 min read File Handling in Ruby 4 min read MethodsRuby | Methods 3 min read Method Visibility in Ruby 3 min read Recursion in Ruby 4 min read Ruby Hook Methods 5 min read Ruby | Range Class Methods 5 min read The Initialize Method in Ruby 2 min read Ruby | Method overriding 2 min read Ruby Date and Time 3 min read OOP ConceptsObject-Oriented Programming in Ruby | Set 1 9 min read Object Oriented Programming in Ruby | Set-2 8 min read Ruby | Class & Object 4 min read Private Classes in Ruby 3 min read Freezing Objects | Ruby 2 min read Ruby | Inheritance 4 min read Polymorphism in Ruby 3 min read Ruby | Constructors 2 min read Ruby | Access Control 8 min read Ruby | Encapsulation 2 min read Ruby Mixins 3 min read Instance Variables in Ruby 3 min read Data Abstraction in Ruby 3 min read Ruby Static Members 3 min read ExceptionsRuby | Exceptions 4 min read Ruby | Exception handling 6 min read Catch and Throw Exception In Ruby 3 min read Raising Exceptions in Ruby 4 min read Ruby | Exception Handling in Threads | Set - 1 2 min read Ruby | Exception Class and its Methods 3 min read Ruby RegexRuby | Regular Expressions 3 min read Ruby Search and Replace 2 min read Ruby ClassesRuby | Float Class 7 min read Ruby | Integer Class 3 min read Ruby | Symbol Class 5 min read Ruby | Struct Class 5 min read Ruby | Dir Class and its methods 3 min read Ruby | MatchData Class 4 min read Ruby ModuleRuby | Module 4 min read Ruby | Comparable Module 3 min read Ruby | Math Module 4 min read Include v/s Extend in Ruby 2 min read Like