Regular Expressions 101

Explanation

Pro

^start of line

Positive Lookahead(?=.*_)

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

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\d{5,8}a digit, repeated between 5 and 8 times

Non-Capturing Group(?:_\d{5,8})*

*repeats the group contents below any number of times:

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\d{5,8}a digit, repeated between 5 and 8 times

_?optionally matches the literal _ (95₁₀ / 137₈ / 5F₁₆)

$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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

^(?=.*_)\d{5,8}(?:_\d{5,8})*_?$

New

123456_123456
12345678_12345678_12345678
123456_12345678_123456_12345678
12345_123456_1234567_12345678_
12334

123456_1
123456_12
123456_1594126781
123_1594126781

Extraction

123456_123456
12345678_12345678_12345678
123456_12345678_123456_12345678
12345_123456_1234567_12345678_
12334

123456_1
123456_12
123456_1594126781
123_1594126781