Regular Expressions 101

Pro

Positive Lookbehind(?<=^(?:\d{6}(?:\d{2})*|(?:\d{3}){1,2}))

^start of line

Non-Capturing Group(?:\d{6}(?:\d{2})*|(?:\d{3}){1,2})

1st Alternative\d{6}(?:\d{2})*

\d{6}a digit, repeated exactly 6 times

Non-Capturing Group(?:\d{2})*

*repeats the group contents below any number of times:

\d{2}a digit, repeated exactly 2 times

2nd Alternative(?:\d{3}){1,2}

Non-Capturing Group(?:\d{3}){1,2}

{1,2}repeats the group contents below between 1 and 2 times:

\d{3}a digit, repeated exactly 3 times

Positive Lookahead(?=\d+$)

\d+a digit, repeated at least once

$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

Detailed match information will be displayed here automatically.

26 tokens

(?<=^(?:\d{6}(?:\d{2})*|(?:\d{3}){1,2}))(?=\d+$)

New

1234567890
1234
123456
1234567
12345678
123456789
1234567890123

1234567890
1234
123456
1234567
12345678
123456789
1234567890123