Regular Expressions 101

Pro

^start of line

Positive Lookahead(?=(I*))

Group 1(I*)

I*the literal I (73₁₀ / 111₈ / 49₁₆) (case sensitive), repeated any number of times

Group 2(^\1|,\2I|\2I)+

+repeats the group contents below at least once:

1st Alternative^\1

^start of line

\1the text saved by group 1

2nd Alternative,\2I

,the literal , (44₁₀ / 54₈ / 2C₁₆)

\2the text saved by group 2

Ithe literal I (73₁₀ / 111₈ / 49₁₆) (case sensitive)

3rd Alternative\2I

\2the text saved by group 2

Ithe literal I (73₁₀ / 111₈ / 49₁₆) (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

Regular Expression

^(?=(I*))(^\1|,\2I|\2I)+$

New

I,II,III,IIII,IIIII,IIIIII,IIIIIII
I,II,III,IIII,IIIII,IIIIII,IIIIIIIIII
II,II,III,IIII,IIIII,IIIIII,IIIIIII
I,II,IIIIII,IIII,IIIII,IIIIII,IIIIIII
IIIIII,IIIIIII
III,IIII,IIIII,IIIIII

Extraction

I,II,III,IIII,IIIII,IIIIII,IIIIIII
I,II,III,IIII,IIIII,IIIIII,IIIIIIIIII
II,II,III,IIII,IIIII,IIIIII,IIIIIII
I,II,IIIIII,IIII,IIIII,IIIIII,IIIIIII
IIIIII,IIIIIII
III,IIII,IIIII,IIIIII