Regular Expressions 101

1st Alternative(?<=^|\s)([a-z])\1*(?!\S)\K

Positive Lookbehind(?<=^|\s)

1st Alternative^

^start of line

2nd Alternative\s

\sany whitespace character

Group 1([a-z])

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\1*the text saved by group 1, repeated any number of times

Negative Lookahead(?!\S)

\Sany non-whitespace character

\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match

2nd Alternative([a-z])\2*(?=\2)

Group 2([a-z])

Character Class[a-z]

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\2*the text saved by group 2, repeated any number of times

Positive Lookahead(?=\2)

\2the text saved by group 2

Global pattern flags

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

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?<=^|\s)([a-z])\1*(?!\S)\K|([a-z])\2*(?=\2)

New

abbbbbc x
test jjka
bbb cca
test hjjjja ppp
xaaa bcccd eee fffg