Regular Expressions 101

^start of string

Positive Lookahead(?=(a(?-1)?b)(?!b))

Group 1(a(?-1)?b)

athe literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive)

(?-1)?optionally calls group 1 as a subroutine

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

Negative Lookahead(?!b)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

a+the literal a (97₁₀ / 141₈ / 61₁₆) (case sensitive), repeated at least once

Positive Lookahead(?=(b(?-1)?c))

Group 2(b(?-1)?c)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

(?-1)?optionally calls group 2 as a subroutine

cthe literal c (99₁₀ / 143₈ / 63₁₆) (case sensitive)

Group 3(b(?-1)?c)

bthe literal b (98₁₀ / 142₈ / 62₁₆) (case sensitive)

(?-1)?optionally calls group 3 as a subroutine

cthe literal c (99₁₀ / 143₈ / 63₁₆) (case sensitive)

$end of string, or before its final line terminator

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

^
  (?=(a(?-1)?b)(?!b))  a+
  (?=(b(?-1)?c)) 
  (b(?-1)?c)
$

New

aaabbbbcccc