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

/
/
gm

Test String

Code Generator

Language

Generated Code

use strict; my $str = 'filename: /usr/lib/modules/5.7.7-967.native/kernel/drivers/video/nvidia.ko alias: char-major-195-* version: 450.57 supported: external license: NVIDIA srcversion: CCB2AEF641D4CD7A82E48B3 alias: pci:v000010DEd*sv*sd*bc03sc02i00* alias: pci:v000010DEd*sv*sd*bc03sc00i00* depends: retpoline: Y name: nvidia vermagic: 5.7.7-967.native SMP mod_unload parm: NvSwitchRegDwords:NvSwitch regkey (charp) parm: NvSwitchBlacklist:NvSwitchBlacklist=uuid[,uuid...] (charp) parm: nv_cap_enable_devfs:nv_cap_enable_devfs=0 or 1 (int) parm: NVreg_ResmanDebugLevel:int parm: NVreg_RmLogonRC:int parm: NVreg_ModifyDeviceFiles:int parm: NVreg_DeviceFileUID:int parm: NVreg_DeviceFileGID:int parm: NVreg_DeviceFileMode:int parm: NVreg_InitializeSystemMemoryAllocations:int parm: NVreg_UsePageAttributeTable:int parm: NVreg_MapRegistersEarly:int parm: NVreg_RegisterForACPIEvents:int parm: NVreg_EnablePCIeGen3:int parm: NVreg_EnableMSI:int parm: NVreg_TCEBypassMode:int parm: NVreg_EnableStreamMemOPs:int parm: NVreg_EnableBacklightHandler:int parm: NVreg_RestrictProfilingToAdminUsers:int parm: NVreg_PreserveVideoMemoryAllocations:int parm: NVreg_DynamicPowerManagement:int parm: NVreg_DynamicPowerManagementVideoMemoryThreshold:int parm: NVreg_EnableUserNUMAManagement:int parm: NVreg_MemoryPoolSize:int parm: NVreg_KMallocHeapMaxSize:int parm: NVreg_VMallocHeapMaxSize:int parm: NVreg_IgnoreMMIOCheck:int parm: NVreg_NvLinkDisable:int parm: NVreg_EnablePCIERelaxedOrderingMode:int parm: NVreg_RegisterPCIDriver:int parm: NVreg_RegistryDwords:charp parm: NVreg_RegistryDwordsPerDevice:charp parm: NVreg_RmMsg:charp parm: NVreg_GpuBlacklist:charp parm: NVreg_TemporaryFilePath:charp parm: NVreg_AssignGpus:charp'; my $regex = qr/(?<=version:\s\s\s\s\s\s\s\s)\d+(\.\d+)+/mp; 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