Regular Expressions 101

1st Alternative^\d{5}(?:-\d{4})?(?!\S)

^start of line

\d{5}a Unicode decimal digit, repeated exactly 5 times

Non-Capturing Group(?:-\d{4})?

?repeats the group contents below at most once:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{4}a Unicode decimal digit, repeated exactly 4 times

Negative Lookahead(?!\S)

\Sany character that is not Unicode whitespace

2nd Alternative(?<!\S)\d{5}(?:-\d{4})?(?=[\r\n]|$)

Negative Lookbehind(?<!\S)

\Sany character that is not Unicode whitespace

\d{5}a Unicode decimal digit, repeated exactly 5 times

Non-Capturing Group(?:-\d{4})?

?repeats the group contents below at most once:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{4}a Unicode decimal digit, repeated exactly 4 times

Positive Lookahead(?=[\r\n]|$)

1st Alternative[\r\n]

Character Class[\r\n]

\ra carriage return (ASCII 13)

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

2nd Alternative$

$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.

Search reference

Regular Expression

^\d{5}(?:-\d{4})?(?!\S)|(?<!\S)\d{5}(?:-\d{4})?(?=[\r\n]|$)

New

Nothing to match in the middle 06000 or 06000-0000 on this line

06111 these are ok 06222-1111

06333-1111 and these 06444

06555-333 these are not 06666-444

06777-66666 also not 06888-77777

06888-00001 but this last one is

06999-9999

Some additional cases here:

12345abc something non-whitespace after it? no

abc12345 something non-whitespace before it? no

Just on its own? yes

12345

Regular Expression

Substitution