Regular Expressions 101

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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"
"
ms

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?ms)(lease\s(?P<ip>[0-9\.]+)\s{.+})`) var str = `lease 10.31.31.131 { starts 0 2014/08/31 14:54:11; ends 0 2014/08/31 15:04:11; cltt 0 2014/08/31 14:54:11; binding state active; next binding state free; rewind binding state free; hardware ethernet d0:e7:82:19:8e:ec; set ddns-rev-name = "131.31.31.10.in-addr.arpa."; set ddns-txt = "0044522956d8e56b0f40798743a0660994"; set ddns-fwd-name = "Chromecast.example."; client-hostname "Chromecast"; } lease 10.31.31.133 { starts 0 2014/08/31 14:54:51; ends 0 2014/08/31 15:04:51; cltt 0 2014/08/31 14:54:51; binding state active; next binding state free; rewind binding state free; hardware ethernet 00:18:0a:22:2f:9f; uid "\001\000\030\012\"/\237"; set ddns-rev-name = "133.31.31.10.in-addr.arpa."; set ddns-txt = "31897a4f3a66a2733b86a7cd3b0b0b2923"; set ddns-fwd-name = "ap-1-00180a222f9f.example."; client-hostname "ap-1-00180a222f9f"; } ` if len(re.FindStringIndex(str)) > 0 { fmt.Println(re.FindString(str),"found at index",re.FindStringIndex(str)[0]) } }

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/