Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!.*(.).*\1)

.*any character (except for line terminators), repeated any number of times

Group 1(.)

.any character (except for line terminators)

.*any character (except for line terminators), repeated any number of times

\1the text saved by group 1

Group 2([abcd]+)

Character Class[abcd]+

+matches at least one character from the set below:

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

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

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

dthe literal d (100₁₀ / 144₈ / 64₁₆) (case sensitive)

$end of line

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.

25 tokens

^(?!.*(.).*\1)([abcd]+)$

New

abcd
abc
aaa
ab
a
abb
abcb
dbca
dbda
bdba
cbad

abcd
abc
aaa
ab
a
abb
abcb
dbca
dbda
bdba
cbad