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

/
/
gxm

Test String

Code Generator

Language

Generated Code

import Foundation let pattern = #"^(?<time>[^ +][-:0-9TZ]+|[[:upper:]][[:lower:]]{2}[ -:+0-9TZ]*)([^ ][+0:]+|\s+)(\s*)(?<host>[^ ][-\w\d]+)(\s*)(?<service>[^ [][-_\w]+)(\[(?<pid>[^ \]][\d]*)\]):\s*((\[\s*(?<mtime>[^ ][\w: \/]+)\]\s*\[\s*(?<severity>[^ ][\w]+)\]\s*){0,1}\s*\[\s*(?<component>[^ ][\w:]+)\]){0,1}\s*(?<message>.*){0,1}.*$"# let regex = try! NSRegularExpression(pattern: pattern, options: [.anchorsMatchLines, .allowCommentsAndWhitespace]) let testString = #""" Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3915] haproxy: [1503580119.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:08:39", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"AMQP serve Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3916] haproxy: [1503580148.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:09:08", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"message re Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3917] haproxy: [1503580151.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:09:11", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"AMQP serve Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3918] haproxy: [1503580164.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:09:24", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"message re Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3919] haproxy: [1503580167.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:09:27", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"AMQP serve Oct 02 12:56:47 ctl01 td-agent-bit[22911]: [3920] haproxy: [1503580172.000000000, {"path"=>"/var/log/sapmock/haproxy.log", "time"=>"2017-08-24T13:09:32", "host"=>"de4-1d-2d-0d-44-a0", "service"=>"ceilometer-polling", "message"=>"AMQP serve Oct 02 12:58:52 ctl01 td-agent-bit[22911]: [engine] caught signal Oct 02 12:58:52 ctl01 td-agent-bit[22911]: [2017/10/02 12:58:52] [ info] [input] pausing tail.0 Oct 02 12:58:52 ctl01 td-agent-bit[22911]: [2017/10/02 12:58:52] [ info] [input] pausing tail.1 Oct 02 12:58:52 ctl01 systemd[1]: Stopping TD Agent Bit... Oct 02 13:00:22 ctl01 systemd[1]: td-agent-bit.service: State 'stop-sigterm' timed out. Killing. Oct 02 13:00:22 ctl01 systemd[1]: td-agent-bit.service: Main process exited, code=killed, status=9/KILL Oct 02 13:00:22 ctl01 systemd[1]: Stopped TD Agent Bit. Oct 02 13:00:22 ctl01 systemd[1]: td-agent-bit.service: Unit entered failed state. Oct 02 13:00:22 ctl01 systemd[1]: td-agent-bit.service: Failed with result 'signal'. Oct 02 13:00:22 ctl01 systemd[1]: Started TD Agent Bit. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [ info] [engine] started Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [in_tail] parser 'rabbitmq' is not registered Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [ warn] [out_es] consider use a tag_key that starts with '_' Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. Oct 02 13:00:22 ctl01 td-agent-bit[23506]: [2017/10/02 13:00:22] [error] [parser:haproxy] Invalid time format %Y-%m-%dT%H:%M:%S. """# let stringRange = NSRange(location: 0, length: testString.utf16.count) let matches = regex.matches(in: testString, range: stringRange) var result: [[String]] = [] for match in matches { var groups: [String] = [] for rangeIndex in 1 ..< match.numberOfRanges { let nsRange = match.range(at: rangeIndex) guard !NSEqualRanges(nsRange, NSMakeRange(NSNotFound, 0)) else { continue } let string = (testString as NSString).substring(with: nsRange) groups.append(string) } if !groups.isEmpty { result.append(groups) } } print(result)

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 Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression