Regular Expressions 101

Negative Lookbehind(?<![\d.])

Character Class[\d.]

\da digit

.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

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

Non-Capturing Group(?:[1-9]?\d|1\d\d|2[0-4]\d|25[0-5])

1st 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

2nd Alternative1\d\d

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da digit

3rd Alternative2[0-4]\d

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

\da digit

4th Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:[1-9]?\d|1\d\d|2[0-4]\d|25[0-5])

1st 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

2nd Alternative1\d\d

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da digit

3rd Alternative2[0-4]\d

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

\da digit

4th Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

Negative Lookahead(?![\d.])

Character Class[\d.]

\da digit

.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?<![\d.])(?:(?:[1-9]?\d|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:[1-9]?\d|1\d\d|2[0-4]\d|25[0-5])(?![\d.])

New

I'm using powershell to run a find/replace across a folder full of log files. Below is a mock up of the type of formatting I'm dealing with. test 127.1.1.1test test 10.0.0.1 test test 172.28.69.77test test 15.26.32.159 test test 15.26.32.1594test test 1.26.3255.1594test test 1555.2655.3255.1594test 255.255.255.192 256.255.255.0 999.999.999.999

Regular Expression

Extraction