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)(?:(?:(public|protected|private)\s+)|(?:(abstract|static)\s+)|(?:(final)\s+)|(?:(volatile|synchronized)\s+)|(?:(native|strictfp)\s+))*([a-zA-Z_][[:alnum:]]+)\s+([a-zA-Z_][[:word:]<>\[\]]+)\s*\(\s*(?:(?:([a-zA-Z_][[:word:]<>\[\]]+)\s+([a-zA-Z_][[:alnum:]]+)\s*)(?:,\s*([a-zA-Z_][[:word:]<>\[\]]+)\s+([a-zA-Z_][[:alnum:]]+)\s*)*)?\)\s*\{`) var str = `cat cut cot c@t$ c?t c t? caut. caat cuut! hello hello world lite.ral $ sign lit\erbl ^ car[a]t Robert Bob Rob Rick Rick lo lol loll lolll lollll lolllll lollllll lolllllll lollllllll lolllllllll lollllllllll lolllllllllll lollllllllllll while (a < b) { while (c < d) { --d;}; while (b < c) { ++a; --c; } } 10001 18052 19146 <b>thing</a> +1 555-234-1234 == matches (654) 999-0234 == matches +1 (101) 234 9838 == matches 333 444.5555 == matches 111.234-3463 == matches +1-333-333-3333 == doesn't match (drops the +1) 555 2341234 == doesn't match (missing a separator) 231-1115 == doesn't match (missing an area code) doowopdoo shoobeedoobee doodoodoo doowop 0 C a@b.c bob@bob.bob steve@steve.co.uk tom.jones@its.not.unusual 0.0 +.03 -100.3 4.5e5 +0.03e-9 .01e12 .e4 -.e public static void main(String[] args) { return; } private double thingDoer (int thingA , float thingB) { while (thingA < thingB) { ++thingA; } return thingA * thingB; } boolean blobber(){ // do blob things return false; } invalidMethodSignature here{ return; } anotherInvalidOne(){ return; }` 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/