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

/
/
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)^\s*\d+\s*:\s*(?:o?|(oo+?)\1+)$`) var str = ` 0 : 1 : o 2 : oo 3 : ooo 4 : oooo 5 : ooooo 6 : oooooo 7 : ooooooo 8 : oooooooo 9 : ooooooooo 10 : oooooooooo 11 : ooooooooooo 12 : oooooooooooo 13 : ooooooooooooo 14 : oooooooooooooo 15 : ooooooooooooooo 16 : oooooooooooooooo 17 : ooooooooooooooooo 18 : oooooooooooooooooo 19 : ooooooooooooooooooo 20 : oooooooooooooooooooo 21 : ooooooooooooooooooooo 22 : oooooooooooooooooooooo 23 : ooooooooooooooooooooooo 24 : oooooooooooooooooooooooo 25 : ooooooooooooooooooooooooo 26 : oooooooooooooooooooooooooo 27 : ooooooooooooooooooooooooooo 28 : oooooooooooooooooooooooooooo 29 : ooooooooooooooooooooooooooooo 30 : oooooooooooooooooooooooooooooo 31 : ooooooooooooooooooooooooooooooo 32 : oooooooooooooooooooooooooooooooo 33 : ooooooooooooooooooooooooooooooooo 34 : oooooooooooooooooooooooooooooooooo 35 : ooooooooooooooooooooooooooooooooooo 36 : oooooooooooooooooooooooooooooooooooo 37 : ooooooooooooooooooooooooooooooooooooo 38 : oooooooooooooooooooooooooooooooooooooo 39 : ooooooooooooooooooooooooooooooooooooooo 40 : oooooooooooooooooooooooooooooooooooooooo 41 : ooooooooooooooooooooooooooooooooooooooooo 42 : oooooooooooooooooooooooooooooooooooooooooo 43 : ooooooooooooooooooooooooooooooooooooooooooo 44 : oooooooooooooooooooooooooooooooooooooooooooo 45 : ooooooooooooooooooooooooooooooooooooooooooooo 46 : oooooooooooooooooooooooooooooooooooooooooooooo 47 : ooooooooooooooooooooooooooooooooooooooooooooooo 48 : oooooooooooooooooooooooooooooooooooooooooooooooo 49 : ooooooooooooooooooooooooooooooooooooooooooooooooo ` 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/