Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

r"
"
gim

Test String

Code Generator

Language

Generated Code

use strict; my $str = 'STEELHEAD-MIB DEFINITIONS ::= BEGIN IMPORTS OBJECT-TYPE, MODULE-IDENTITY, NOTIFICATION-TYPE, Unsigned32, TimeTicks, IpAddress, Counter32, Counter64 FROM SNMPv2-SMI DateAndTime FROM SNMPv2-TC products FROM RBT-MIB; steelhead MODULE-IDENTITY LAST-UPDATED "201401070000Z" ORGANIZATION "Riverbed Technology, Inc." CONTACT-INFO " Riverbed Technical Support support@riverbed.com" DESCRIPTION "Steelhead MIB" REVISION "201401070000Z" DESCRIPTION "Connection forwarding cluster incompatible trap" REVISION "201301250000Z" DESCRIPTION "Corrections in descriptions of some traps" REVISION "201210170000Z" DESCRIPTION "Added trap for CF Peer IPv6 incompatible alarm" REVISION "201202030000Z" DESCRIPTION "Updated for 7.0.1" ::= { products 1 } system OBJECT IDENTIFIER ::= { steelhead 1 } status OBJECT IDENTIFIER ::= { steelhead 2 } config OBJECT IDENTIFIER ::= { steelhead 3 } alarms OBJECT IDENTIFIER ::= { steelhead 4 } statistics OBJECT IDENTIFIER ::= { steelhead 5 } -- -- -- SYSTEM -- -- model OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-only STATUS current DESCRIPTION "Appliance model" ::= { system 1 } serialNumber OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-only STATUS current DESCRIPTION "Appliance serial number" ::= { system 2 } systemVersion OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-only STATUS current DESCRIPTION "System software version string" ::= { system 3 } -- -- -- STATUS -- -- systemClock OBJECT-TYPE SYNTAX DateAndTime MAX-ACCESS read-only STATUS current DESCRIPTION "System clock time" ::= { status 1 } health OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-only STATUS current DESCRIPTION "Current health of the system. The value is one amongst Healthy, Admission Control, Degraded, Critical" ::= { status 2 } serviceStatus OBJECT-TYPE SYNTAX OCTET STRING MAX-ACCESS read-only STATUS current DESCRIPTION "Current status of the optimization service" ::= { status 3 }'; my $regex = qr/^\w+(?=\s+OBJECT-TYPE)/imp; if ( $str =~ /$regex/g ) { print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n"; # print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n"; # print "Capture Group 2 is $2 ... and so on\n"; } # ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p' # Named capture groups can be called via $+{name}

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html