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

/
/
g

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`\(PERMBLOCK\)\s(?<IP>[.0-9]*)\s\((?<country>.{2}).*? - (?<date>.*)`) var str = `180.76.15.158 # lfd: (PERMBLOCK) 180.76.15.158 (CN/China/baiduspider-180-76-15-158.crawl.baidu.com) has had more than 4 temp blocks in the last 86400 secs - Mon Jun 11 05:20:35 2018 80.211.140.69 # lfd: (PERMBLOCK) 80.211.140.69 (IT/Italy/host69-140-211-80.serverdedicati.aruba.it) has had more than 4 temp blocks in the last 86400 secs - Mon Jun 11 05:39:16 2018 94.65.235.31 # lfd: (PERMBLOCK) 94.65.235.31 (GR/Greece/ppp-94-65-235-31.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Mon Jun 11 18:40:52 2018 94.71.194.156 # lfd: (PERMBLOCK) 94.71.194.156 (GR/Greece/athedsl-4511380.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Tue Jun 12 02:24:44 2018 114.207.112.188 # lfd: (PERMBLOCK) 114.207.112.188 (KR/Republic of Korea/114-207-112-188.tongkni.co.kr) has had more than 4 temp blocks in the last 86400 secs - Tue Jun 12 12:12:10 2018 94.64.71.183 # lfd: (PERMBLOCK) 94.64.71.183 (GR/Greece/ppp-94-64-71-183.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Wed Jun 13 03:54:37 2018 89.210.18.91 # lfd: (PERMBLOCK) 89.210.18.91 (GR/Greece/ppp089210018091.access.hol.gr) has had more than 4 temp blocks in the last 86400 secs - Wed Jun 13 04:07:48 2018 94.65.149.72 # lfd: (PERMBLOCK) 94.65.149.72 (GR/Greece/ppp-94-65-149-72.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Fri Jun 15 05:22:46 2018 94.64.70.87 # lfd: (PERMBLOCK) 94.64.70.87 (GR/Greece/ppp-94-64-70-87.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Sun Jun 17 07:06:11 2018 94.64.66.189 # lfd: (PERMBLOCK) 94.64.66.189 (GR/Greece/ppp-94-64-66-189.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Mon Jun 18 00:28:35 2018 180.76.15.6 # lfd: (PERMBLOCK) 180.76.15.6 (CN/China/baiduspider-180-76-15-6.crawl.baidu.com) has had more than 4 temp blocks in the last 86400 secs - Tue Jun 19 22:15:29 2018 94.65.145.144 # lfd: (PERMBLOCK) 94.65.145.144 (GR/Greece/ppp-94-65-145-144.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Wed Jun 20 01:13:08 2018 180.76.15.145 # lfd: (PERMBLOCK) 180.76.15.145 (CN/China/baiduspider-180-76-15-145.crawl.baidu.com) has had more than 4 temp blocks in the last 86400 secs - Thu Jun 21 13:55:36 2018 2.84.214.95 # lfd: (PERMBLOCK) 2.84.214.95 (GR/Greece/ppp-2-84-214-95.home.otenet.gr) has had more than 4 temp blocks in the last 86400 secs - Thu Jun 21 20:39:07 2018` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

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 Golang, please visit: https://golang.org/pkg/regexp/