Regular Expressions 101

^start of line

Negative Lookahead(?!.*\b(\d+)\b.*\b\1\b)

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

\ban ASCII word boundary

Group 1(\d+)

\d+a digit, repeated at least once

\ban ASCII word boundary

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

\ban ASCII word boundary

\1the text saved by group 1

\ban ASCII word boundary

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d*a digit, repeated any number of times

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Non-Capturing Group(?:, *[1-9]\d* *)*

*repeats the group contents below any number of times:

,the literal , (44₁₀ / 54₈ / 2C₁₆)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d*a digit, repeated any number of times

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

$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

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Search reference

Regular Expression

^(?!.*\b(\d+)\b.*\b\1\b) *[1-9]\d* *(?:, *[1-9]\d* *)*$

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