Regular Expressions 101

Explanation

Pro

^start of line

Non-Capturing Group(?:\d+\.\d+\.(?:\d+\.)*(?=.*\n\d+\.\d+\.(?:\d+\.)*)|\d+\.\d+\.(?:\d+\.)*(?!.*\n))

1st Alternative\d+\.\d+\.(?:\d+\.)*(?=.*\n\d+\.\d+\.(?:\d+\.)*)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:\d+\.)*

*repeats the group contents below any number of times:

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Positive Lookahead(?=.*\n\d+\.\d+\.(?:\d+\.)*)

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

\na line-feed (newline) character (ASCII 10)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:\d+\.)*

*repeats the group contents below any number of times:

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

2nd Alternative\d+\.\d+\.(?:\d+\.)*(?!.*\n)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:\d+\.)*

*repeats the group contents below any number of times:

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Negative Lookahead(?!.*\n)

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

\na line-feed (newline) character (ASCII 10)

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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

^(?:\d+\.\d+\.(?:\d+\.)*(?=.*\n\d+\.\d+\.(?:\d+\.)*)|\d+\.\d+\.(?:\d+\.)*(?!.*\n))

1.2.
3.4.5.
5.6.7.10