Regular Expressions 101

Explanation

Pro

Negative Lookbehind(?<!\d)

\da digit

Non-Capturing Group(?:[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])

1st Alternative[01]?[0-9]{1,2}

Character Class[01]?

?matches at most one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{1,2}

{1,2}matches between 1 and 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative2[0-4][0-9]

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

0-4one character from 0 (48₁₀) to 4 (52₁₀)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

3rd Alternative25[0-5]

25the literal text 25

Character Class[0-5]

0-5one character from 0 (48₁₀) to 5 (53₁₀)

Non-Capturing Group(?:\.(?:[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])){3}

{3}repeats the group contents below exactly 3 times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])

1st Alternative[01]?[0-9]{1,2}

Character Class[01]?

?matches at most one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{1,2}

{1,2}matches between 1 and 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative2[0-4][0-9]

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

0-4one character from 0 (48₁₀) to 4 (52₁₀)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

3rd Alternative25[0-5]

25the literal text 25

Character Class[0-5]

0-5one character from 0 (48₁₀) to 5 (53₁₀)

Non-Capturing Group(?::\d{1,5})?+

?+repeats the group contents below at most once:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\d{1,5}a digit, repeated between 1 and 5 times

Negative Lookahead(?!\d|\t*offline)

1st Alternative\d

\da digit

2nd Alternative\t*offline

\t*a tab character (ASCII 9), repeated any number of times

offlinethe literal text offline (case sensitive)

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

25 tokens

Regular Expression

(?<!\d)(?:[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])(?:\.(?:[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])){3}(?::\d{1,5})?+(?!\d|\t*offline)

Unit Tests

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