regex101: Grab valid LAN IPs

Pro

(?xm)applies the following effective flags to the remainder of the pattern: gxm

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Definition Group(?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )

Group byte(?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d)

1st Alternative 2[0-4]\d

2the literal text 2

Character Class[0-4]

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

\da digit

2nd Alternative 25[0-5]

25the literal text 25

Character Class[0-5]

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

3rd Alternative 1\d\d

1the literal text 1

\da digit

4th Alternative [1-9]?\d

Character Class[1-9]?

?matches at most one character from the set below:

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

\da digit

^start of line

Group 2(10 (?:\.(?&byte)){3} | 172 \. (?: 1 [6-9] | 2\d | 3[01] ) (?:\.(?&byte)){2} | 192 \. 168 (?:\.(?&byte)){2} | )

1st Alternative10 (?:\.(?&byte)){3}

10 the literal text 10

Non-Capturing Group(?:\.(?&byte)){3}

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

(?&byte)calls group byte as a subroutine

2nd Alternative 172 \. (?: 1 [6-9] | 2\d | 3[01] ) (?:\.(?&byte)){2}

172 the literal text 172

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?: 1 [6-9] | 2\d | 3[01] )

1st Alternative 1 [6-9]

1 the literal text 1

Character Class[6-9]

6-9one character from 6 (54₁₀) to 9 (57₁₀)

2nd Alternative 2\d

2the literal text 2

\da digit

3rd Alternative 3[01]

3the literal text 3

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Non-Capturing Group(?:\.(?&byte)){2}

{2}repeats the group contents below exactly 2 times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

(?&byte)calls group byte as a subroutine

3rd Alternative 192 \. 168 (?:\.(?&byte)){2}

192 the literal text 192

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

168 the literal text 168

Non-Capturing Group(?:\.(?&byte)){2}

{2}repeats the group contents below exactly 2 times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

(?&byte)calls group byte as a subroutine

4th Alternative — matches an empty string

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

25 tokens

Regular Expression

(?xm) (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) ^ (10 (?:\.(?&byte)){3} | 172 \. (?: 1 [6-9] | 2\d | 3[01] ) (?:\.(?&byte)){2} | 192 \. 168 (?:\.(?&byte)){2} | ) $

New

10.0.0.0
10.1.2.3
10.255.255.255
172.16.0.0
172.25.1.2.3
172.31.255.255
12.34.56.78
123.456.789.0
192.168.0.555
192.168.0.0
192.168.1.2
192.168.255.255

Substitution

10.0.0.0
10.1.2.3
10.255.255.255
172.16.0.0
172.25.1.2.3
172.31.255.255
12.34.56.78
123.456.789.0
192.168.0.555
192.168.0.0
192.168.1.2
192.168.255.255