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"
"
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)(?:(?P<Day1>\d{1,2})(?:\W*(?P<Month1>[A-Z][a-z]*\b))|(?:(?P<Month2>[A-Z][a-z]*\b)\W*)(?:(?P<Day2>\d{1,2})(?:\b|th|st|nd))?|(?P<Month3>\d{1,2})\W+(?P<Day3>\d{1,2})|(?P<Month4>\d{1,2}))?\W+?(?P<Year>\d{2,4}(?=$|;))`) var str = `04/20/2009 04/20/09 4/20/09 4/3/09 Mar-20-2009 Mar 20, 2009 March 20, 2009 Mar. 20, 2009 Mar 20 2009; 20 Mar 2009 20 March 2009 20 Mar. 2009 20 March, 2009 Mar 20th, 2009 Mar 21st, 2009 Mar 22nd, 2009 Feb 2009 Sep 2009 Oct 2010 6/2008 12/2009 2009 2010` 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/