Regular Expressions 101

Explanation

Pro

^start of line

Group 1([0]?[1-9]|[1-2]\d|3[0-1])

1st Alternative[0]?[1-9]

Character Class[0]?

?matches at most one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[1-9]

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

2nd Alternative[1-2]\d

Character Class[1-2]

1-2one character from 1 (49₁₀) to 2 (50₁₀)

\da digit

3rd Alternative3[0-1]

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

Character Class[0-1]

0-1one character from 0 (48₁₀) to 1 (49₁₀)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Group 2(JAN|FEB|MAR|APR|MAY|JUN|JULY|AUG|SEP|OCT|NOV|DEC)

1st AlternativeJAN

JANthe literal text JAN (case sensitive)

2nd AlternativeFEB

FEBthe literal text FEB (case sensitive)

3rd AlternativeMAR

MARthe literal text MAR (case sensitive)

4th AlternativeAPR

APRthe literal text APR (case sensitive)

5th AlternativeMAY

MAYthe literal text MAY (case sensitive)

6th AlternativeJUN

JUNthe literal text JUN (case sensitive)

7th AlternativeJULY

JULYthe literal text JULY (case sensitive)

8th AlternativeAUG

AUGthe literal text AUG (case sensitive)

9th AlternativeSEP

SEPthe literal text SEP (case sensitive)

10th AlternativeOCT

OCTthe literal text OCT (case sensitive)

11th AlternativeNOV

NOVthe literal text NOV (case sensitive)

12th AlternativeDEC

DECthe literal text DEC (case sensitive)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[1-2]

1-2one character from 1 (49₁₀) to 2 (50₁₀)

\d{3}a digit, repeated exactly 3 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

Unit Test Summary

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Quick Reference

26 tokens

Regular Expression

^([0]?[1-9]|[1-2]\d|3[0-1])-(JAN|FEB|MAR|APR|MAY|JUN|JULY|AUG|SEP|OCT|NOV|DEC)-[1-2]\d{3}$

Unit Tests

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